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#1
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OK...not the thermostat, now what? HELP!
Recap: Recently, boat started overheating for approx. 2 to 4 minutes
after startup. Temp goes to 220+F then it suddenly drops back to 150F and stays there, then all is fine until I get to my destination. The obvious culprit (I thought) was a faulty, sticky thermostat. I figured the thermostat simply does not open when it is supposed to (at approx. 160F) but eventually it does and the water cooling happens. Bought a new thermostat and replaced: no luck. Removed the thermostat entirely, closed the housing and started the boat: needle creeped up to 200+! Went home and tested both (old and new) thermostat in hot water: both appear to open at around 160F. So, it appears the problem is NOT the thermostat. I also disconnected the hose from the transom to the thermostat housing (the one drawing the water from the ocean). Started the boat for a few seconds and got a good flow so apparently no clogged intake either. I am assuming that water was pushed through by the impeller so that would mean the impeller is also doing its job (although I have actually not looked in there and impeller was replaced 2 months ago).. Now what? I am not sure what else to check. The alternator belt seems tight so I am also assuming the water pump is running at the correct speed (but I don't really know). In the manual, they list the typical symptoms of overheating (loose belt, clogged intakes, bad hoses, defective thermostat, worn or damaged stern drive water pump). Pretty much the stuff discussed above but also a couple that I have no clue what they are talking about: a) Excessively advanced or retarded ignition timing (????) b) Leakage of air or exhaust into the suction side of the stern water pump (????) I am not very mechanically inclined so I get lost quickly in the jargon. Anyone can offer suggestions, advices, comments, recommendations? I am getting desperate! Problem is I have a cabin that is boat-access only so no boat = stay home instead of enjoying a gorgeous weekend at the cabin...  Andre |
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#2
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Melandre wrote: Recap: Recently, boat started overheating for approx. 2 to 4 minutes after startup. Temp goes to 220+F then it suddenly drops back to 150F and stays there, then all is fine until I get to my destination. The obvious culprit (I thought) was a faulty, sticky thermostat. I figured the thermostat simply does not open when it is supposed to (at approx. 160F) but eventually it does and the water cooling happens. Bought a new thermostat and replaced: no luck. Removed the thermostat entirely, closed the housing and started the boat: needle creeped up to 200+! Went home and tested both (old and new) thermostat in hot water: both appear to open at around 160F. So, it appears the problem is NOT the thermostat. I also disconnected the hose from the transom to the thermostat housing (the one drawing the water from the ocean). Started the boat for a few seconds and got a good flow so apparently no clogged intake either. I am assuming that water was pushed through by the impeller so that would mean the impeller is also doing its job (although I have actually not looked in there and impeller was replaced 2 months ago).. Now what? I am not sure what else to check. The alternator belt seems tight so I am also assuming the water pump is running at the correct speed (but I don't really know). In the manual, they list the typical symptoms of overheating (loose belt, clogged intakes, bad hoses, defective thermostat, worn or damaged stern drive water pump). Pretty much the stuff discussed above but also a couple that I have no clue what they are talking about: a) Excessively advanced or retarded ignition timing (????) b) Leakage of air or exhaust into the suction side of the stern water pump (????) I am not very mechanically inclined so I get lost quickly in the jargon. Anyone can offer suggestions, advices, comments, recommendations? I am getting desperate! Problem is I have a cabin that is boat-access only so no boat = stay home instead of enjoying a gorgeous weekend at the cabin... Andre Aha. Depending on the accuracy of your description...... How fast does the temp climb to 220-250. Within 2 minutes or so after startup? How "suddenly" does it drop from 220 to 150? Your coolant will only cool so fast, so if it seems unnaturally quick it could be as simple as the sending unit. Since the thermostats passed the candy thermometer test, you know you have one good one and one spare. Sending unit is probably less expensive than a lot of other things you could fiddle around replacing, and if the temperature is changing by radical amounts in very short periods of time it is a reasonable suspect. |
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#4
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The sender is a sensor which screws into the engine water jacket and changes
resistance as engine heats up or cools down. Since you gauge changes very fast, maybe the sender, gauge, or wiring problem is present. At this point, it may be a good idea to have a professional marine shop check your problem out. Just let them know what was all done so far which should reduce the costs.. "Melandre" wrote in message ... It takes a couple of minutes to get passed "normal temperature". Then another minute or so to climb over 200F. Then stays hot for 1 to 3 minutes (in a few occasions a bit longer than 3 minutes), then it drops back from well over 200F to 150F in about 3 - 5 seconds. I am not sure what you mean by "sending unit" but if you suggests that perhaps only the readout on the dashboard is screwed up, I doubt it because, for these few freaky minutes, I can really tell the engine is overheating (burning oil smell, block starts smoking a bit). Or maybe you are referring to yet another part that I am not aware of... It is also a simple raw water cooling system (not a closed one with coolant). Andre On 19 Aug 2005 22:15:49 -0700, wrote: Melandre wrote: Recap: Recently, boat started overheating for approx. 2 to 4 minutes after startup. Temp goes to 220+F then it suddenly drops back to 150F and stays there, then all is fine until I get to my destination. The obvious culprit (I thought) was a faulty, sticky thermostat. I figured the thermostat simply does not open when it is supposed to (at approx. 160F) but eventually it does and the water cooling happens. Bought a new thermostat and replaced: no luck. Removed the thermostat entirely, closed the housing and started the boat: needle creeped up to 200+! Went home and tested both (old and new) thermostat in hot water: both appear to open at around 160F. So, it appears the problem is NOT the thermostat. I also disconnected the hose from the transom to the thermostat housing (the one drawing the water from the ocean). Started the boat for a few seconds and got a good flow so apparently no clogged intake either. I am assuming that water was pushed through by the impeller so that would mean the impeller is also doing its job (although I have actually not looked in there and impeller was replaced 2 months ago).. Now what? I am not sure what else to check. The alternator belt seems tight so I am also assuming the water pump is running at the correct speed (but I don't really know). In the manual, they list the typical symptoms of overheating (loose belt, clogged intakes, bad hoses, defective thermostat, worn or damaged stern drive water pump). Pretty much the stuff discussed above but also a couple that I have no clue what they are talking about: a) Excessively advanced or retarded ignition timing (????) b) Leakage of air or exhaust into the suction side of the stern water pump (????) I am not very mechanically inclined so I get lost quickly in the jargon. Anyone can offer suggestions, advices, comments, recommendations? I am getting desperate! Problem is I have a cabin that is boat-access only so no boat = stay home instead of enjoying a gorgeous weekend at the cabin... Andre Aha. Depending on the accuracy of your description...... How fast does the temp climb to 220-250. Within 2 minutes or so after startup? How "suddenly" does it drop from 220 to 150? Your coolant will only cool so fast, so if it seems unnaturally quick it could be as simple as the sending unit. Since the thermostats passed the candy thermometer test, you know you have one good one and one spare. Sending unit is probably less expensive than a lot of other things you could fiddle around replacing, and if the temperature is changing by radical amounts in very short periods of time it is a reasonable suspect. |
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#5
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A possibility ... until the thermostat opens, cooling water from the
impeller has to go somewhere as well as cool the manifolds etc. My understanding, a spring loaded t-valve accomplishes this (V6, V8). When I first disconnected the lines for winter storage, I came across this mechanism and wondered what it was. Perhaps this mechanism is at fault (stuck open a bit ... I dunno) ... and since you're in salt water you might consider a 140 (ok, 143) degree thermostat ... my understanding at 160+ the salt will separate from the water. Go to the bottom of this page to see the t-valve (nylon I guess balls spring loaded) which easily accessible by removing the water lines http://www.perfprotech.com/home/tech...oling-tips.htm "Melandre" wrote in message ... Recap: Recently, boat started overheating for approx. 2 to 4 minutes after startup. Temp goes to 220+F then it suddenly drops back to 150F and stays there, then all is fine until I get to my destination. The obvious culprit (I thought) was a faulty, sticky thermostat. I figured the thermostat simply does not open when it is supposed to (at approx. 160F) but eventually it does and the water cooling happens. Bought a new thermostat and replaced: no luck. Removed the thermostat entirely, closed the housing and started the boat: needle creeped up to 200+! Went home and tested both (old and new) thermostat in hot water: both appear to open at around 160F. So, it appears the problem is NOT the thermostat. I also disconnected the hose from the transom to the thermostat housing (the one drawing the water from the ocean). Started the boat for a few seconds and got a good flow so apparently no clogged intake either. I am assuming that water was pushed through by the impeller so that would mean the impeller is also doing its job (although I have actually not looked in there and impeller was replaced 2 months ago).. Now what? I am not sure what else to check. The alternator belt seems tight so I am also assuming the water pump is running at the correct speed (but I don't really know). In the manual, they list the typical symptoms of overheating (loose belt, clogged intakes, bad hoses, defective thermostat, worn or damaged stern drive water pump). Pretty much the stuff discussed above but also a couple that I have no clue what they are talking about: a) Excessively advanced or retarded ignition timing (????) b) Leakage of air or exhaust into the suction side of the stern water pump (????) I am not very mechanically inclined so I get lost quickly in the jargon. Anyone can offer suggestions, advices, comments, recommendations? I am getting desperate! Problem is I have a cabin that is boat-access only so no boat = stay home instead of enjoying a gorgeous weekend at the cabin... Andre |
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#6
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It's also possible you have something really weird wrong with the
engine. Like a head gasket leak that allows combustion gasses to air-lock the cooling water flow. As the engine warms up, thermal expansion causes the leak to stop, and the system returns to normal. Just a thought. JR Melandre wrote: It takes a couple of minutes to get passed "normal temperature". Then another minute or so to climb over 200F. Then stays hot for 1 to 3 minutes (in a few occasions a bit longer than 3 minutes), then it drops back from well over 200F to 150F in about 3 - 5 seconds. I am not sure what you mean by "sending unit" but if you suggests that perhaps only the readout on the dashboard is screwed up, I doubt it because, for these few freaky minutes, I can really tell the engine is overheating (burning oil smell, block starts smoking a bit). Or maybe you are referring to yet another part that I am not aware of... It is also a simple raw water cooling system (not a closed one with coolant). Andre On 19 Aug 2005 22:15:49 -0700, wrote: Melandre wrote: Recap: Recently, boat started overheating for approx. 2 to 4 minutes after startup. Temp goes to 220+F then it suddenly drops back to 150F and stays there, then all is fine until I get to my destination. The obvious culprit (I thought) was a faulty, sticky thermostat. I figured the thermostat simply does not open when it is supposed to (at approx. 160F) but eventually it does and the water cooling happens. Bought a new thermostat and replaced: no luck. Removed the thermostat entirely, closed the housing and started the boat: needle creeped up to 200+! Went home and tested both (old and new) thermostat in hot water: both appear to open at around 160F. So, it appears the problem is NOT the thermostat. I also disconnected the hose from the transom to the thermostat housing (the one drawing the water from the ocean). Started the boat for a few seconds and got a good flow so apparently no clogged intake either. I am assuming that water was pushed through by the impeller so that would mean the impeller is also doing its job (although I have actually not looked in there and impeller was replaced 2 months ago).. Now what? I am not sure what else to check. The alternator belt seems tight so I am also assuming the water pump is running at the correct speed (but I don't really know). In the manual, they list the typical symptoms of overheating (loose belt, clogged intakes, bad hoses, defective thermostat, worn or damaged stern drive water pump). Pretty much the stuff discussed above but also a couple that I have no clue what they are talking about: a) Excessively advanced or retarded ignition timing (????) b) Leakage of air or exhaust into the suction side of the stern water pump (????) I am not very mechanically inclined so I get lost quickly in the jargon. Anyone can offer suggestions, advices, comments, recommendations? I am getting desperate! Problem is I have a cabin that is boat-access only so no boat = stay home instead of enjoying a gorgeous weekend at the cabin... Andre Aha. Depending on the accuracy of your description...... How fast does the temp climb to 220-250. Within 2 minutes or so after startup? How "suddenly" does it drop from 220 to 150? Your coolant will only cool so fast, so if it seems unnaturally quick it could be as simple as the sending unit. Since the thermostats passed the candy thermometer test, you know you have one good one and one spare. Sending unit is probably less expensive than a lot of other things you could fiddle around replacing, and if the temperature is changing by radical amounts in very short periods of time it is a reasonable suspect. -- -------------------------------------------------------------- Home Page: http://www.seanet.com/~jasonrnorth |
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#7
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Melandre wrote: It takes a couple of minutes to get passed "normal temperature". Then another minute or so to climb over 200F. Then stays hot for 1 to 3 minutes (in a few occasions a bit longer than 3 minutes), then it drops back from well over 200F to 150F in about 3 - 5 seconds. We can be very certain that the cooling system isn't actually dropping in temp for over 200F to 150F in 3-5 seconds. If you're getting a report of a condition that seems virtually impossible, one of the first things to check is the data itself. You sending unit is almost certainly a screw-in unit with a wire attached to it. A new one would be very inexpensive. I am not sure what you mean by "sending unit" but if you suggests that perhaps only the readout on the dashboard is screwed up, I doubt it because, for these few freaky minutes, I can really tell the engine is overheating (burning oil smell, block starts smoking a bit). Or maybe you are referring to yet another part that I am not aware of... It is also a simple raw water cooling system (not a closed one with coolant). Andre |
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#8
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I been in the auto repair industry and have yet to come by a headgasket that
would seal up when heated. But I guess there is always a first. "JR North" wrote in message ... It's also possible you have something really weird wrong with the engine. Like a head gasket leak that allows combustion gasses to air-lock the cooling water flow. As the engine warms up, thermal expansion causes the leak to stop, and the system returns to normal. Just a thought. JR Melandre wrote: It takes a couple of minutes to get passed "normal temperature". Then another minute or so to climb over 200F. Then stays hot for 1 to 3 minutes (in a few occasions a bit longer than 3 minutes), then it drops back from well over 200F to 150F in about 3 - 5 seconds. I am not sure what you mean by "sending unit" but if you suggests that perhaps only the readout on the dashboard is screwed up, I doubt it because, for these few freaky minutes, I can really tell the engine is overheating (burning oil smell, block starts smoking a bit). Or maybe you are referring to yet another part that I am not aware of... It is also a simple raw water cooling system (not a closed one with coolant). Andre On 19 Aug 2005 22:15:49 -0700, wrote: Melandre wrote: Recap: Recently, boat started overheating for approx. 2 to 4 minutes after startup. Temp goes to 220+F then it suddenly drops back to 150F and stays there, then all is fine until I get to my destination. The obvious culprit (I thought) was a faulty, sticky thermostat. I figured the thermostat simply does not open when it is supposed to (at approx. 160F) but eventually it does and the water cooling happens. Bought a new thermostat and replaced: no luck. Removed the thermostat entirely, closed the housing and started the boat: needle creeped up to 200+! Went home and tested both (old and new) thermostat in hot water: both appear to open at around 160F. So, it appears the problem is NOT the thermostat. I also disconnected the hose from the transom to the thermostat housing (the one drawing the water from the ocean). Started the boat for a few seconds and got a good flow so apparently no clogged intake either. I am assuming that water was pushed through by the impeller so that would mean the impeller is also doing its job (although I have actually not looked in there and impeller was replaced 2 months ago).. Now what? I am not sure what else to check. The alternator belt seems tight so I am also assuming the water pump is running at the correct speed (but I don't really know). In the manual, they list the typical symptoms of overheating (loose belt, clogged intakes, bad hoses, defective thermostat, worn or damaged stern drive water pump). Pretty much the stuff discussed above but also a couple that I have no clue what they are talking about: a) Excessively advanced or retarded ignition timing (????) b) Leakage of air or exhaust into the suction side of the stern water pump (????) I am not very mechanically inclined so I get lost quickly in the jargon. Anyone can offer suggestions, advices, comments, recommendations? I am getting desperate! Problem is I have a cabin that is boat-access only so no boat = stay home instead of enjoying a gorgeous weekend at the cabin... Andre Aha. Depending on the accuracy of your description...... How fast does the temp climb to 220-250. Within 2 minutes or so after startup? How "suddenly" does it drop from 220 to 150? Your coolant will only cool so fast, so if it seems unnaturally quick it could be as simple as the sending unit. Since the thermostats passed the candy thermometer test, you know you have one good one and one spare. Sending unit is probably less expensive than a lot of other things you could fiddle around replacing, and if the temperature is changing by radical amounts in very short periods of time it is a reasonable suspect. -- -------------------------------------------------------------- Home Page: http://www.seanet.com/~jasonrnorth |
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#9
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Is it possible that you are getting an air gap in the engine ? Without
water in the cooling channels the motor will heat up fast and cool quickly one the thermostat opens and you get water flowing. Check the water outlet for bubbles when starting the engine. |
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#10
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Another two possibilities. I'm not clear whether you have a sal****er
cooling system or a heat exchanger system. If you have raw water cooling one possibility is rust flakes in the passages in the head. I've seen heads and heat exchangers plugged almost solid. This likely wouldn't be the case if your temp drops back to normal. But keep it in mind if the engine is raw water cooled and hasn't been checked or cleaned for a while. The other possibility is that you have an airlock in the system. Maybe a looped water hose or something like that? Don "Melandre" wrote in message ... Recap: Recently, boat started overheating for approx. 2 to 4 minutes after startup. Temp goes to 220+F then it suddenly drops back to 150F and stays there, then all is fine until I get to my destination. The obvious culprit (I thought) was a faulty, sticky thermostat. I figured the thermostat simply does not open when it is supposed to (at approx. 160F) but eventually it does and the water cooling happens. Bought a new thermostat and replaced: no luck. Removed the thermostat entirely, closed the housing and started the boat: needle creeped up to 200+! Went home and tested both (old and new) thermostat in hot water: both appear to open at around 160F. So, it appears the problem is NOT the thermostat. I also disconnected the hose from the transom to the thermostat housing (the one drawing the water from the ocean). Started the boat for a few seconds and got a good flow so apparently no clogged intake either. I am assuming that water was pushed through by the impeller so that would mean the impeller is also doing its job (although I have actually not looked in there and impeller was replaced 2 months ago).. Now what? I am not sure what else to check. The alternator belt seems tight so I am also assuming the water pump is running at the correct speed (but I don't really know). In the manual, they list the typical symptoms of overheating (loose belt, clogged intakes, bad hoses, defective thermostat, worn or damaged stern drive water pump). Pretty much the stuff discussed above but also a couple that I have no clue what they are talking about: a) Excessively advanced or retarded ignition timing (????) b) Leakage of air or exhaust into the suction side of the stern water pump (????) I am not very mechanically inclined so I get lost quickly in the jargon. Anyone can offer suggestions, advices, comments, recommendations? I am getting desperate! Problem is I have a cabin that is boat-access only so no boat = stay home instead of enjoying a gorgeous weekend at the cabin... Andre |
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