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1986 Johnson 70 Overheating
I recently purchased a boat that has 2 1986 Johnson 70 motors on it.
On the first run out we noticed that the temperature guage for one of them went up to the top of the red while the other stayed in the bottom 1/3rd of the green. We stopped the motors and took the covers off and put our hands on both of the heads near the spark plugs. The one that had stayed in the green was barely warm and the one that was in the red was hot enough to bother your hand if you left it resting on it for 30 seconds. We had actually never gone more than about 1/3rd throttle on either engine for no more than about 5 minutes. And the one in the red had only been at idle except for about 30 seconds when I had put it up to about 1/3rd throttle. The pee stream on both motors looked good. But on the one that was in the red, the pee stream was even stronger - actually stronger than I have ever seen on outboards. I replaced the thermostat because I was thinking that the impeller was good because the pee stream was so good. But it still climbs up to the red after just a few minutes at idle - and then the powerhead feels hot to the touch - not like it burns your hand - but again uncomfortable if you leave your hand on it for a while. Any ideas what the next step should be? I called the local boat guys and they are all at least 2 weeks out and halibut season opens Thursday - so I would like to get a chance to use the boat before 2 weeks from now. Thanks, Eldon |
1986 Johnson 70 Overheating
Eldon Cutlip wrote:
I recently purchased a boat that has 2 1986 Johnson 70 motors on it. On the first run out we noticed that the temperature guage for one of them went up to the top of the red while the other stayed in the bottom 1/3rd of the green. We stopped the motors and took the covers off and put our hands on both of the heads near the spark plugs. The one that had stayed in the green was barely warm and the one that was in the red was hot enough to bother your hand if you left it resting on it for 30 seconds. We had actually never gone more than about 1/3rd throttle on either engine for no more than about 5 minutes. And the one in the red had only been at idle except for about 30 seconds when I had put it up to about 1/3rd throttle. The pee stream on both motors looked good. But on the one that was in the red, the pee stream was even stronger - actually stronger than I have ever seen on outboards. I replaced the thermostat because I was thinking that the impeller was good because the pee stream was so good. But it still climbs up to the red after just a few minutes at idle - and then the powerhead feels hot to the touch - not like it burns your hand - but again uncomfortable if you leave your hand on it for a while. Any ideas what the next step should be? I called the local boat guys and they are all at least 2 weeks out and halibut season opens Thursday - so I would like to get a chance to use the boat before 2 weeks from now. Thanks, Eldon If you can hold your hand on it for 30 seconds, it's actually running cold. It sounds like the gauge is inaccurate. There was no factory provision for sending units on these engines except for the warning horn switch, so the installation is suspect, too. A count to about -6- before it gets too hot for your hand on the thermostat housing is normal operating temperature. Maybe the pee stream on the colder engine is weak because the thermostat is stuck open or someone has removed it. Rob |
1986 Johnson 70 Overheating
If I remove the thermostat from the one that is running hot (or at
least hotter), should that then duplicate the cold one - with the hand test? And if so, that should prove the guage is the culprit? Thanks, Eldon trainfan1 wrote in message ... Eldon Cutlip wrote: I recently purchased a boat that has 2 1986 Johnson 70 motors on it. On the first run out we noticed that the temperature guage for one of them went up to the top of the red while the other stayed in the bottom 1/3rd of the green. We stopped the motors and took the covers off and put our hands on both of the heads near the spark plugs. The one that had stayed in the green was barely warm and the one that was in the red was hot enough to bother your hand if you left it resting on it for 30 seconds. We had actually never gone more than about 1/3rd throttle on either engine for no more than about 5 minutes. And the one in the red had only been at idle except for about 30 seconds when I had put it up to about 1/3rd throttle. The pee stream on both motors looked good. But on the one that was in the red, the pee stream was even stronger - actually stronger than I have ever seen on outboards. I replaced the thermostat because I was thinking that the impeller was good because the pee stream was so good. But it still climbs up to the red after just a few minutes at idle - and then the powerhead feels hot to the touch - not like it burns your hand - but again uncomfortable if you leave your hand on it for a while. Any ideas what the next step should be? I called the local boat guys and they are all at least 2 weeks out and halibut season opens Thursday - so I would like to get a chance to use the boat before 2 weeks from now. Thanks, Eldon If you can hold your hand on it for 30 seconds, it's actually running cold. It sounds like the gauge is inaccurate. There was no factory provision for sending units on these engines except for the warning horn switch, so the installation is suspect, too. A count to about -6- before it gets too hot for your hand on the thermostat housing is normal operating temperature. Maybe the pee stream on the colder engine is weak because the thermostat is stuck open or someone has removed it. Rob |
1986 Johnson 70 Overheating
I took the thermostat out of the "hot" one and then ran it on the
"ears." The engine stayed dead cold for as long as I ran it (probably a few minutes). But the pee hole just dribbled a drop or so every few seconds - no stream. Then I put the thermostat back in and it had a good stream at the pee hole but the engine started heating up again. Should I still get a good stream even with the thermostat out - if the water pump is good? I know the powerhead was getting water because it stayed dead cold and I saw water when I pulled the thermostat cover. Thanks, Eldon trainfan1 wrote in message ... Eldon Cutlip wrote: I recently purchased a boat that has 2 1986 Johnson 70 motors on it. On the first run out we noticed that the temperature guage for one of them went up to the top of the red while the other stayed in the bottom 1/3rd of the green. We stopped the motors and took the covers off and put our hands on both of the heads near the spark plugs. The one that had stayed in the green was barely warm and the one that was in the red was hot enough to bother your hand if you left it resting on it for 30 seconds. We had actually never gone more than about 1/3rd throttle on either engine for no more than about 5 minutes. And the one in the red had only been at idle except for about 30 seconds when I had put it up to about 1/3rd throttle. The pee stream on both motors looked good. But on the one that was in the red, the pee stream was even stronger - actually stronger than I have ever seen on outboards. I replaced the thermostat because I was thinking that the impeller was good because the pee stream was so good. But it still climbs up to the red after just a few minutes at idle - and then the powerhead feels hot to the touch - not like it burns your hand - but again uncomfortable if you leave your hand on it for a while. Any ideas what the next step should be? I called the local boat guys and they are all at least 2 weeks out and halibut season opens Thursday - so I would like to get a chance to use the boat before 2 weeks from now. Thanks, Eldon If you can hold your hand on it for 30 seconds, it's actually running cold. It sounds like the gauge is inaccurate. There was no factory provision for sending units on these engines except for the warning horn switch, so the installation is suspect, too. A count to about -6- before it gets too hot for your hand on the thermostat housing is normal operating temperature. Maybe the pee stream on the colder engine is weak because the thermostat is stuck open or someone has removed it. Rob |
1986 Johnson 70 Overheating
Eldon Cutlip wrote:
I took the thermostat out of the "hot" one and then ran it on the "ears." The engine stayed dead cold for as long as I ran it (probably a few minutes). But the pee hole just dribbled a drop or so every few seconds - no stream. Then I put the thermostat back in and it had a good stream at the pee hole but the engine started heating up again. Should I still get a good stream even with the thermostat out - if the water pump is good? I know the powerhead was getting water because it stayed dead cold and I saw water when I pulled the thermostat cover. Thanks, Eldon trainfan1 wrote in message ... Eldon Cutlip wrote: I recently purchased a boat that has 2 1986 Johnson 70 motors on it. On the first run out we noticed that the temperature guage for one of them went up to the top of the red while the other stayed in the bottom 1/3rd of the green. We stopped the motors and took the covers off and put our hands on both of the heads near the spark plugs. The one that had stayed in the green was barely warm and the one that was in the red was hot enough to bother your hand if you left it resting on it for 30 seconds. We had actually never gone more than about 1/3rd throttle on either engine for no more than about 5 minutes. And the one in the red had only been at idle except for about 30 seconds when I had put it up to about 1/3rd throttle. The pee stream on both motors looked good. But on the one that was in the red, the pee stream was even stronger - actually stronger than I have ever seen on outboards. I replaced the thermostat because I was thinking that the impeller was good because the pee stream was so good. But it still climbs up to the red after just a few minutes at idle - and then the powerhead feels hot to the touch - not like it burns your hand - but again uncomfortable if you leave your hand on it for a while. Any ideas what the next step should be? I called the local boat guys and they are all at least 2 weeks out and halibut season opens Thursday - so I would like to get a chance to use the boat before 2 weeks from now. Thanks, Eldon If you can hold your hand on it for 30 seconds, it's actually running cold. It sounds like the gauge is inaccurate. There was no factory provision for sending units on these engines except for the warning horn switch, so the installation is suspect, too. A count to about -6- before it gets too hot for your hand on the thermostat housing is normal operating temperature. Maybe the pee stream on the colder engine is weak because the thermostat is stuck open or someone has removed it. Rob With the thermostat out the pressure will fall off. Hence my suspicion of your "cold" motor. The thermostats should be closed, or substantially so, until around 150 degrees, and then they will let 150 degree or warmer water by. You can test them on your kitchen stove with a candy thermometer if you must. Where are your sending units? Rob |
1986 Johnson 70 Overheating
If you want to eliminate the gauges, disconnect both sending units and
temporarily run a wire from the cool motor to the one showing hot and one from the hot motor to the one running cool. If the problem now shows on the one that was running cool, you know you have a bad gauge. -- Bill Chesapeake, Va "Eldon Cutlip" wrote in message m... If I remove the thermostat from the one that is running hot (or at least hotter), should that then duplicate the cold one - with the hand test? And if so, that should prove the guage is the culprit? Thanks, Eldon trainfan1 wrote in message ... Eldon Cutlip wrote: I recently purchased a boat that has 2 1986 Johnson 70 motors on it. On the first run out we noticed that the temperature guage for one of them went up to the top of the red while the other stayed in the bottom 1/3rd of the green. We stopped the motors and took the covers off and put our hands on both of the heads near the spark plugs. The one that had stayed in the green was barely warm and the one that was in the red was hot enough to bother your hand if you left it resting on it for 30 seconds. We had actually never gone more than about 1/3rd throttle on either engine for no more than about 5 minutes. And the one in the red had only been at idle except for about 30 seconds when I had put it up to about 1/3rd throttle. The pee stream on both motors looked good. But on the one that was in the red, the pee stream was even stronger - actually stronger than I have ever seen on outboards. I replaced the thermostat because I was thinking that the impeller was good because the pee stream was so good. But it still climbs up to the red after just a few minutes at idle - and then the powerhead feels hot to the touch - not like it burns your hand - but again uncomfortable if you leave your hand on it for a while. Any ideas what the next step should be? I called the local boat guys and they are all at least 2 weeks out and halibut season opens Thursday - so I would like to get a chance to use the boat before 2 weeks from now. Thanks, Eldon If you can hold your hand on it for 30 seconds, it's actually running cold. It sounds like the gauge is inaccurate. There was no factory provision for sending units on these engines except for the warning horn switch, so the installation is suspect, too. A count to about -6- before it gets too hot for your hand on the thermostat housing is normal operating temperature. Maybe the pee stream on the colder engine is weak because the thermostat is stuck open or someone has removed it. Rob |
1986 Johnson 70 Overheating
trainfan1 wrote in message ...
Eldon Cutlip wrote: I took the thermostat out of the "hot" one and then ran it on the "ears." The engine stayed dead cold for as long as I ran it (probably a few minutes). But the pee hole just dribbled a drop or so every few seconds - no stream. Then I put the thermostat back in and it had a good stream at the pee hole but the engine started heating up again. Should I still get a good stream even with the thermostat out - if the water pump is good? I know the powerhead was getting water because it stayed dead cold and I saw water when I pulled the thermostat cover. Thanks, Eldon trainfan1 wrote in message ... Eldon Cutlip wrote: I recently purchased a boat that has 2 1986 Johnson 70 motors on it. On the first run out we noticed that the temperature guage for one of them went up to the top of the red while the other stayed in the bottom 1/3rd of the green. We stopped the motors and took the covers off and put our hands on both of the heads near the spark plugs. The one that had stayed in the green was barely warm and the one that was in the red was hot enough to bother your hand if you left it resting on it for 30 seconds. We had actually never gone more than about 1/3rd throttle on either engine for no more than about 5 minutes. And the one in the red had only been at idle except for about 30 seconds when I had put it up to about 1/3rd throttle. The pee stream on both motors looked good. But on the one that was in the red, the pee stream was even stronger - actually stronger than I have ever seen on outboards. I replaced the thermostat because I was thinking that the impeller was good because the pee stream was so good. But it still climbs up to the red after just a few minutes at idle - and then the powerhead feels hot to the touch - not like it burns your hand - but again uncomfortable if you leave your hand on it for a while. Any ideas what the next step should be? I called the local boat guys and they are all at least 2 weeks out and halibut season opens Thursday - so I would like to get a chance to use the boat before 2 weeks from now. Thanks, Eldon If you can hold your hand on it for 30 seconds, it's actually running cold. It sounds like the gauge is inaccurate. There was no factory provision for sending units on these engines except for the warning horn switch, so the installation is suspect, too. A count to about -6- before it gets too hot for your hand on the thermostat housing is normal operating temperature. Maybe the pee stream on the colder engine is weak because the thermostat is stuck open or someone has removed it. Rob With the thermostat out the pressure will fall off. Hence my suspicion of your "cold" motor. The thermostats should be closed, or substantially so, until around 150 degrees, and then they will let 150 degree or warmer water by. You can test them on your kitchen stove with a candy thermometer if you must. Where are your sending units? Rob I don't know where my sending units are. For the Mercury engines I've had I always got a nice shop manual for the specific engine from Mercury. I haven't had a chance to get one for these Johnsons yet. I do see a wire coming out of the power head just left of the thermostat that I was guessing might be it. I was thinking that even with the thermostat completely removed that the pee hole should still have a stream of some kind - so I was thinking my water pump was suspect. Are you saying that with the thermostat completely out the pressure is reduced enough so that the pee hole may just dribble (with no stream) and my water pump may still be good? If so, maybe I should just replace the thermostat on the cold one and see if it "warms up?" If it does I could then do a "hand test" to see if they are both pretty close to the same heat range? And I could also see if their guages start reading close to the same heat range? Unfortunately these thermostats are weird plastic ones that I've never seen before and I don't think I would be able to see anything if I boiled them. And more unfortunate is I won't be back home until Friday evening to continue working on this. I really appreciate your help. I haven't really even got a chance to try this boat out because of this problem and I'm really dying to. I did schedule an appointment in 2 weeks with the mechanic. But the sooner I can get it worked out the sooner I can try out the boat :) Thanks, Eldon |
1986 Johnson 70 Overheating
I don't know where my sending units are. For the Mercury engines I've had I always got a nice shop manual for the specific engine from Mercury. I haven't had a chance to get one for these Johnsons yet. I do see a wire coming out of the power head just left of the thermostat that I was guessing might be it. I was thinking that even with the thermostat completely removed that the pee hole should still have a stream of some kind - so I was thinking my water pump was suspect. Are you saying that with the thermostat completely out the pressure is reduced enough so that the pee hole may just dribble (with no stream) and my water pump may still be good? If so, maybe I should just replace the thermostat on the cold one and see if it "warms up?" If it does I could then do a "hand test" to see if they are both pretty close to the same heat range? And I could also see if their guages start reading close to the same heat range? Unfortunately these thermostats are weird plastic ones that I've never seen before and I don't think I would be able to see anything if I boiled them. And more unfortunate is I won't be back home until Friday evening to continue working on this. I really appreciate your help. I haven't really even got a chance to try this boat out because of this problem and I'm really dying to. I did schedule an appointment in 2 weeks with the mechanic. But the sooner I can get it worked out the sooner I can try out the boat :) Thanks, Eldon You should have metal OMC# 396987 143 degree thermostats in those engines. This is a recirculating system, and at low displacement speeds (the water pump - not the vessel) you will have a drop in pressure as your "warm" water is wasted out the exhaust relief and exhaust hub without the thermostat in place. It may even be low when the pump reaches centrifugal speeds. Put known good thermostats in and check your water jacket temp. I think you will be alright. Rob |
1986 Johnson 70 Overheating
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1986 Johnson 70 Overheating
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1986 Johnson 70 Overheating
Well, I replaced the thermostat in the cold motor. And I tried to find
"heat sticks" and nobody in the 3 auto part stores I went to knew what they were. They did sell some laser things starting at about $100. But I couldn't justify that for a one time deal. After replacing the thermostat in the cold motor, it went up to about mid-way in the red at idle. And my wife and I put our hands on the thermostat housing after letting it idle in the red for about 5 minutes or so and counted to between 3 and 4 seconds until we had to pull our hands off it. I ran the "hot" motor and it ended up just slightly higher than mid-way in the red and we could put our hands on the thermostat housing for between 4 and 5 seconds. So, I was figuring that the guages just weren't the right ones for this engine and that the engines were running fine. I then took them out on the water and both of them were idling in the red (about mid-way). I then opened them up to about 2000 or so rpms and they both cooled down to about mid-green. Then I think let them idle again and the "hot" engine got to the top of the red again. So, I shut that one off and ran the "cool" engine for a few minutes around 4000 rpms and I looked down and saw that one was up in the red. That kind of surprised me because I had been thinking that at least the "cold" motor would run well. The other day we had run that one for a good 20 minutes at the same speed and it stayed in the green (that was before we put the new thermostat in). Then we decided to head back - and I kind of took turns with the motors trying to keep them as cool as I could. Just before we got back we heard what I suspect was an overheat alarm beep. So I shut them both off and tried to get anchored - but we were in the way in the harbor by that time. When I turned the key back on for the cold motor we just heard a steady alarm. So I turned the key back on the for hot motor and puttered over - but it was running "rough" by then I would say - it shut off once by itself - and it didn't start right up that time. So, I was thinking I must need have a semi-bad impeller in both motors at this point. So, I just took apart the lower unit and pulled the water pump on the cold motor. The impeller looked fine - no wear or tear and still quite bendy. The inside of the water pump lining doesn't have any scratches. So now I'm totally out of ideas. At this point I'm believing the guages - since the overheat alarm sounded. Is it possible I replaced the old thermostat that was stuck wide open in the cold motor with a thermostat rated for a different temperature? The new one looked the same as the old one (wierd plastic things - kind of look like some kind of practice tips for archery (but too big and plastic) with threads on the "shank" side that don't seem to thread into anything). But I did notice the old one has 10LT stamped on it and the new ones I got have G1C stamped on them. Any ideas are GREATLY appreciated! Eldon |
1986 Johnson 70 Overheating
"Eldon Cutlip" wrote in message om... So, I was thinking I must need have a semi-bad impeller in both motors at this point. So, I just took apart the lower unit and pulled the water pump on the cold motor. The impeller looked fine - no wear or tear and still quite bendy. The inside of the water pump lining doesn't have any scratches. So now I'm totally out of ideas. Replace the impellers. even if they look good they may not be. A few years ago my dad was up in Canada fishing and the engine was running hot. Removed the leg and "flipped" the impeller over. The engine ran fine the rest of the trip. The impeller got changed ASAP! Greg |
1986 Johnson 70 Overheating
"Greg O" wrote in message ...
"Eldon Cutlip" wrote in message om... So, I was thinking I must need have a semi-bad impeller in both motors at this point. So, I just took apart the lower unit and pulled the water pump on the cold motor. The impeller looked fine - no wear or tear and still quite bendy. The inside of the water pump lining doesn't have any scratches. So now I'm totally out of ideas. Replace the impellers. even if they look good they may not be. A few years ago my dad was up in Canada fishing and the engine was running hot. Removed the leg and "flipped" the impeller over. The engine ran fine the rest of the trip. The impeller got changed ASAP! Greg I replaced the water pump in the "cold" motor - or at least the one that was cold originally :) After that, I had just enough time to idle it for 5 or 10 minutes on the ears. It settled right at the mark between the green and red. I didn't have a chance to get the other engine's water pump done yet or to take the cold one out on the water. But something still seems wrong even with the cold motor. I think I will have to buy one of those laser temperature things. And I think someone had mentioned that the oil to fuel mixture may be suspect. Could running too lean cause the engines to run hotter? If so how do I verify what the oil mixture is set to (these are the VRO Johnson 70's - 1986)? I had two of the local boat mechanics tell me the new thermostats are the same as the ones I replaced. So, I think the plan right now is replace the other water pump, get a laser, and verify the oil mixture. I have no clue how to verify the oil mixture but I guess I could just put oil in the fuel tank and see if they stay cooler. Thanks, Eldon |
1986 Johnson 70 Overheating
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1986 Johnson 70 Overheating
On 19 May 2004 08:40:19 -0700, (Eldon Cutlip)
wrote: Derek wrote in message . .. On 18 May 2004 08:40:40 -0700, (Eldon Cutlip) wrote: "Greg O" wrote in message ... "Eldon Cutlip" wrote in message om... So, I was thinking I must need have a semi-bad impeller in both motors at this point. So, I just took apart the lower unit and pulled the water pump on the cold motor. The impeller looked fine - no wear or tear and still quite bendy. The inside of the water pump lining doesn't have any scratches. So now I'm totally out of ideas. Replace the impellers. even if they look good they may not be. A few years ago my dad was up in Canada fishing and the engine was running hot. Removed the leg and "flipped" the impeller over. The engine ran fine the rest of the trip. The impeller got changed ASAP! Greg I replaced the water pump in the "cold" motor - or at least the one that was cold originally :) After that, I had just enough time to idle it for 5 or 10 minutes on the ears. It settled right at the mark between the green and red. I didn't have a chance to get the other engine's water pump done yet or to take the cold one out on the water. But something still seems wrong even with the cold motor. I think I will have to buy one of those laser temperature things. And I think someone had mentioned that the oil to fuel mixture may be suspect. Could running too lean cause the engines to run hotter? If so how do I verify what the oil mixture is set to (these are the VRO Johnson 70's - 1986)? I had two of the local boat mechanics tell me the new thermostats are the same as the ones I replaced. So, I think the plan right now is replace the other water pump, get a laser, and verify the oil mixture. I have no clue how to verify the oil mixture but I guess I could just put oil in the fuel tank and see if they stay cooler. Thanks, Eldon Without verifying that both your gauges are accurate and reliable.. ...... you could be farting against thunder! Well, my thinking was that the laser temperature gun would tell me exactly what temperature my engines are running at. I thought I could then see what the guage was reading and "mentally calibrate" for my guages. How else can I verify my guages are accurate and reliable? Eldon Wal-Mart sells mechanical temp gauges (made by Equius) for around $10. They come with a good selection of fittings and mine is very accurate. You should be able to install a "T" piece fitting that will accept both your electric gauge and the mechanical one simultaniously. Try vairying the the engine conditions (NEVER rev a motor above 2000 r.p.m. in neutral). The two gauges should follow each other closely. Now, test the other motor. All done for around $15. Just be careful not to kink the temp gauge line, it's filled with liquid (alcohol, I think). Ideally, this test should be performed under normal operating conditions. Another method, but do this at your own risk, is to ground out the wire to the sender unit via a selection of various resistors. For example, if a 500 Ohm resistor takes the gauge to half, and a 200 Ohm takes it to one quarter, it MUST do the same on the other gauge. Next, remove the sender units and put them in a pot of warm water for a bit. Using a digital multimeter, record the Ohms readings of both. Heat the water a little more and repeat, all the way up to near boiling. I'm guessing the readings should be within about 5% of each other. Remember to make the readings quickly, for accuracy. Problem is, if they're way out, which one is faulty???? This is why I preffer a mechanical gauge over an electric gauge whenever possible, even for Volts (joke!). Unfortunately, the pivoting and steering system of a boat does not lend itself to these gauges, unless they're mounted on the motor directly (another temporary option). Okay, since I have a few minutes, and it were my boat, here's what I'd do (at your own risk of course) 1) Replace the other impellor (water pump). 2) Ensure that all the seals between the pump and the head are good. You could even be losing water pressure/volume from a leaking seal or joint somewhere along that pipe (been there, done that). 3) Remove both thermostats, and leave housings open. BRIEFLY run engines at idle and a little above. Both "fountains" should be similar in volume and pressure (use drums, not ear muffs, for a true simulation.) 4) Verify that both thermostats are working similarly, by using the pot on a stove method. 5) Verify that both temperature gauges are accurate/reliable. (also check for and clean any corrosion on any terminals). Basically, you start at the beginning (pump) and logically eliminate any discrepencies between the 2 motors. I would also suggest getting a manual for your motor. They are invaluable. Good Luck. |
1986 Johnson 70 Overheating
Wal-Mart sells mechanical temp gauges (made by Equius) for around $10. They come with a good selection of fittings and mine is very accurate. You should be able to install a "T" piece fitting that will accept both your electric gauge and the mechanical one simultaniously. Try vairying the the engine conditions (NEVER rev a motor above 2000 r.p.m. in neutral). The two gauges should follow each other closely. Now, test the other motor. All done for around $15. Just be careful not to kink the temp gauge line, it's filled with liquid (alcohol, I think). Ideally, this test should be performed under normal operating conditions. Another method, but do this at your own risk, is to ground out the wire to the sender unit via a selection of various resistors. For example, if a 500 Ohm resistor takes the gauge to half, and a 200 Ohm takes it to one quarter, it MUST do the same on the other gauge. Next, remove the sender units and put them in a pot of warm water for a bit. Using a digital multimeter, record the Ohms readings of both. Heat the water a little more and repeat, all the way up to near boiling. I'm guessing the readings should be within about 5% of each other. Remember to make the readings quickly, for accuracy. Problem is, if they're way out, which one is faulty???? This is why I preffer a mechanical gauge over an electric gauge whenever possible, even for Volts (joke!). Unfortunately, the pivoting and steering system of a boat does not lend itself to these gauges, unless they're mounted on the motor directly (another temporary option). Okay, since I have a few minutes, and it were my boat, here's what I'd do (at your own risk of course) 1) Replace the other impellor (water pump). 2) Ensure that all the seals between the pump and the head are good. You could even be losing water pressure/volume from a leaking seal or joint somewhere along that pipe (been there, done that). 3) Remove both thermostats, and leave housings open. BRIEFLY run engines at idle and a little above. Both "fountains" should be similar in volume and pressure (use drums, not ear muffs, for a true simulation.) 4) Verify that both thermostats are working similarly, by using the pot on a stove method. 5) Verify that both temperature gauges are accurate/reliable. (also check for and clean any corrosion on any terminals). Basically, you start at the beginning (pump) and logically eliminate any discrepencies between the 2 motors. I would also suggest getting a manual for your motor. They are invaluable. Good Luck. I really appreciate your time on this! I just got the manual via UPS and my wife ordered one of the temperature laser gun things. And I will be starting through your suggestions starting with the water pump in the "hot" engine when I get back home this weekend. Thanks! Eldon |
1986 Johnson 70 Overheating
"Derek" wrote Wal-Mart sells mechanical temp gauges (made by Equius) for around $10. They come with a good selection of fittings and mine is very accurate. Which department at Walmart did you find it in? Cam |
1986 Johnson 70 Overheating
On Thu, 20 May 2004 08:37:22 -0800, "Camilo"
wrote: "Derek" wrote Wal-Mart sells mechanical temp gauges (made by Equius) for around $10. They come with a good selection of fittings and mine is very accurate. Which department at Walmart did you find it in? Cam The Auto section, where they keep all the oil, Volt, Amp etc. gauges for cars. They're pretty common at auto accesorie stores. I've seen them at Canadian Tire here in Canada too. |
1986 Johnson 70 Overheating
"Eldon Cutlip" wrote in message om... I really appreciate your time on this! I just got the manual via UPS and my wife ordered one of the temperature laser gun things. And I will be starting through your suggestions starting with the water pump in the "hot" engine when I get back home this weekend. Thanks! Eldon Be sure you install the factory water pump kit #432995 which contains everything you need to replace it plus items to upgrade your cooling system. You will get a different thermostat spring and a plastic water tell-tale fitting that get relocated to the top of the exhaust housing to purge trapped air in the system. Remember that your temperature gauges are not precision instruments and that the sender is only reading "skin temperature" of the motor, which may be higher or lower than the internal water temp of the engine. Keep us posted Bill Grannis service manager |
1986 Johnson 70 Overheating
I replaced the water pump in the "hot" engine. So, that meant I had
replaced the water pump in both engines and thermostats in both engines. Someone else had already moved the pee hole connector to the top of the exhaust housing on both engines. And someone else must have already upgraded the springs on the thermostats. Because the kit said I should just replace the straight spring that was in there with the same straight string in the water pump kit. So I think I should be good on all the water pump conversion things. I then ran both engines (at idle on the ears) and they both got into the red on my guages. The laser gun showed up to about 135 degrees at the front of the thermostat housing and up to about 170 degrees (varying though) at lower parts of the power head. So I decided I better take it to the local professional before I screwed things up. The mechanic called and said both engines were running great. He said they were both below 150 degrees and that they ran them up to 2000 rpms. He said he believed the sending units on the guages were bad because they looked pretty corroded. He said he was going to see when he could get some in and maybe look at getting me set up with water pressure guages instead (he thought they would be a better indicator of a good cooling system - and I still have the overheat warning horn). But then he called back later and said they do not make the sending units or guages for my motors anymore. He cleaned up my sending units and replaced them. I took the boat out for the next three days and the motors appeared to work great. No overheat alarm. When one of the guages got up into the red the corresponding motor appeared to be smoking more than when the guage showed in the green. I was wondering if that could have something to do with the fact that I mixed the gas in the tank 100 to 1 as a safeguard because I was afraid the guages going in the red might be because the mix was too lean. Does that seem possible at all? Also, do any of you guys know what the part numbers for the sending units and guages would be and where I might be able to find obsolete parts like those? My motors are 1986 Johnson 70hp - model: J70TLCD I bought a parts manual but it doesn't seem to include part numbers for the sending unit and temperature guages. Thanks very much for the help! Eldon |
1986 Johnson 70 Overheating
"Eldon Cutlip" wrote in message m... I replaced the water pump in the "hot" engine. So, that meant I had replaced the water pump in both engines and thermostats in both engines. Also, do any of you guys know what the part numbers for the sending units and guages would be and where I might be able to find obsolete parts like those? My motors are 1986 Johnson 70hp - model: J70TLCD I bought a parts manual but it doesn't seem to include part numbers for the sending unit and temperature guages. Part number 175410 from Johnson or Evinrude is the complete water temperature gauge kit for an outboard motor. Bill Grannis service manager |
1986 Johnson 70 Overheating
"Billgran" wrote in message ...
"Eldon Cutlip" wrote in message m... I replaced the water pump in the "hot" engine. So, that meant I had replaced the water pump in both engines and thermostats in both engines. Also, do any of you guys know what the part numbers for the sending units and guages would be and where I might be able to find obsolete parts like those? My motors are 1986 Johnson 70hp - model: J70TLCD I bought a parts manual but it doesn't seem to include part numbers for the sending unit and temperature guages. Part number 175410 from Johnson or Evinrude is the complete water temperature gauge kit for an outboard motor. Bill Grannis service manager Thanks! Is that the one that will work with my 1986 J70TLCD outboards? And do you know any sources for that? My local mechanic told me they didn't make sending units or guages for my outboards anymore. Eldon |
1986 Johnson 70 Overheating
"Eldon Cutlip" wrote in message om... Part number 175410 from Johnson or Evinrude is the complete water temperature gauge kit for an outboard motor. Bill Grannis service manager Thanks! Is that the one that will work with my 1986 J70TLCD outboards? And do you know any sources for that? My local mechanic told me they didn't make sending units or guages for my outboards anymore. Eldon I don't have one of those handy, but I think it's just the sender and the gauge and you would have to use your original sender bracket. Late model motors have a tapped hole for the senders. Your "mechanic" may be mistaken about gauges being unavailable since Teleflex makes a whole series of gauges that include an outboard water temp version. Go to teleflex.com The Teleflex part numbers for a common style a OB water temp gauge 72622 sender 52320-010 Z bracket IA55009 Any marine store or supplier can order these for you. Bill Grannis service manager |
1986 Johnson 70 Overheating
hi eldon,
when mixing oil for 2-stroke 100 to 1 means you used less oil and less protection to the engine and runs hotter. For instance I run 50 to 1 mix of 2-stroke oil. So in a gallon of gas is 128 ounces of fuel. At 50 to 1, I mix 12.8 ounces of marine 2-stroke oil for 5 gallons of fuel. I have a mixing cup to measure my fuel mixture. (128 divide by 50 = 2.56 times 5 = 12.8) I think I am correct. greg "Eldon Cutlip" wrote in message m... I replaced the water pump in the "hot" engine. So, that meant I had replaced the water pump in both engines and thermostats in both engines. Someone else had already moved the pee hole connector to the top of the exhaust housing on both engines. And someone else must have already upgraded the springs on the thermostats. Because the kit said I should just replace the straight spring that was in there with the same straight string in the water pump kit. So I think I should be good on all the water pump conversion things. I then ran both engines (at idle on the ears) and they both got into the red on my guages. The laser gun showed up to about 135 degrees at the front of the thermostat housing and up to about 170 degrees (varying though) at lower parts of the power head. So I decided I better take it to the local professional before I screwed things up. The mechanic called and said both engines were running great. He said they were both below 150 degrees and that they ran them up to 2000 rpms. He said he believed the sending units on the guages were bad because they looked pretty corroded. He said he was going to see when he could get some in and maybe look at getting me set up with water pressure guages instead (he thought they would be a better indicator of a good cooling system - and I still have the overheat warning horn). But then he called back later and said they do not make the sending units or guages for my motors anymore. He cleaned up my sending units and replaced them. I took the boat out for the next three days and the motors appeared to work great. No overheat alarm. When one of the guages got up into the red the corresponding motor appeared to be smoking more than when the guage showed in the green. I was wondering if that could have something to do with the fact that I mixed the gas in the tank 100 to 1 as a safeguard because I was afraid the guages going in the red might be because the mix was too lean. Does that seem possible at all? Also, do any of you guys know what the part numbers for the sending units and guages would be and where I might be able to find obsolete parts like those? My motors are 1986 Johnson 70hp - model: J70TLCD I bought a parts manual but it doesn't seem to include part numbers for the sending unit and temperature guages. Thanks very much for the help! Eldon |
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