Home |
Search |
Today's Posts |
#1
posted to rec.boats
|
|||
|
|||
Base timing vs. ignition timing
Reading my shop manual for my 4.3L 190hp carb'd Merc I see that it
describes setting the "base timing" as well as the "ignition timing". Both procedures look almost the same so what is the difference? Also, it says you must set the "Dwell" before timing the boat; what is that? The procedure for setting idle and mix on the carb is very complex in the manual. They say you have to be in the water to do it. In old cars I would just set the mix about one turn rich of when the car started to run rough and I'd set the idle based on the tach. Why can't you do the same on a boat? -Robert |
#2
posted to rec.boats
|
|||
|
|||
Base timing vs. ignition timing
On Jun 13, 1:47*pm, "Robert M. Gary" wrote:
Reading my shop manual for my 4.3L 190hp carb'd Merc I see that it describes setting the "base timing" as well as the "ignition timing". Both procedures look almost the same so what is the difference? Also, it says you must set the "Dwell" before timing the boat; what is that? The procedure for setting idle and mix on the carb is very complex in the manual. They say you have to be in the water to do it. In old cars I would just set the mix about one turn rich of when the car started to run rough and I'd set the idle based on the tach. Why can't you do the same on a boat? -Robert Dwell is an angular measurement, simply put, it is a measurement of how long the points, or electronic module is in a closed state. It's easily checked with a dwell meter. |
#3
posted to rec.boats
|
|||
|
|||
Base timing vs. ignition timing
On Jun 13, 11:03*am, wrote:
Dwell is an angular measurement, simply put, it is a measurement of how long the points, or electronic module is in a closed state. It's easily checked with a dwell meter. Cool, I'm going to buy http://www.harborfreight.com/cpi/cta...emnumber=95670 -Robert |
#4
posted to rec.boats
|
|||
|
|||
Base timing vs. ignition timing
On Jun 13, 1:47 pm, "Robert M. Gary" wrote:
Reading my shop manual for my 4.3L 190hp carb'd Merc I see that it describes setting the "base timing" as well as the "ignition timing". Both procedures look almost the same so what is the difference? Also, it says you must set the "Dwell" before timing the boat; what is that? The procedure for setting idle and mix on the carb is very complex in the manual. They say you have to be in the water to do it. In old cars I would just set the mix about one turn rich of when the car started to run rough and I'd set the idle based on the tach. Why can't you do the same on a boat? -Robert "The Cam angle, or dwell angle is the number of degrees through which the distributor cam rotates while the breaker points are closed. It is directly related to the breaker point gap. Decreasing the breaker point gap will increase the cam angle. If the cam angle is too small, the current will have insufficient time to pass though the primary winding of the ignition coil, and a weaker spark will result. If the cam angle is too great, the breaker points will not open far enough, they will tend to stick together, and misfiring will result. The best method of adjusting breaker points is by means of a dwell meter." From http://www.pelicanparts.com/techarti...914_timing.htm It has been a while since I messed with a dwell meter but if I recall correctly the engine needs to be running, thus the need for the boat to be in the water. It can be done with the boat out of water but muffs would have to be used on the lower drive unit water intakes. |
#5
posted to rec.boats
|
|||
|
|||
Base timing vs. ignition timing
"Robert M. Gary" wrote in message ... Reading my shop manual for my 4.3L 190hp carb'd Merc I see that it describes setting the "base timing" as well as the "ignition timing". Both procedures look almost the same so what is the difference? Also, it says you must set the "Dwell" before timing the boat; what is that? The procedure for setting idle and mix on the carb is very complex in the manual. They say you have to be in the water to do it. In old cars I would just set the mix about one turn rich of when the car started to run rough and I'd set the idle based on the tach. Why can't you do the same on a boat? -Robert Dwell is measured with a dwell meter, and is more precise than setting the point gap with a feeler gauge. Base timing is most likely with no advance and Ignition timing is running at a certain rpm. You can check to see if the advance weights or point base plate are stuck or the springs are bad by checking timing at different RPM's. In the old days a lot of auto parts house had distributor testers where you could check all the advance curves with the distributor out of the engine. |
#6
posted to rec.boats
|
|||
|
|||
Base timing vs. ignition timing
"Robert M. Gary" wrote in message
... Reading my shop manual for my 4.3L 190hp carb'd Merc I see that it describes setting the "base timing" as well as the "ignition timing". Both procedures look almost the same so what is the difference? Also, it says you must set the "Dwell" before timing the boat; what is that? The procedure for setting idle and mix on the carb is very complex in the manual. They say you have to be in the water to do it. In old cars I would just set the mix about one turn rich of when the car started to run rough and I'd set the idle based on the tach. Why can't you do the same on a boat? -Robert So you have confirmed that your boat has points? The service manual only covers your model? Dwell is the point gap. Truth is that a feeler gauge is accurate enough for setting the points. There is considerable tolerance. A timing light is the best way to set the time. Make sure the boat is at the correct idle first. Few boats have a vacuum advance but in the cases where they do it is typical to set the idle with it disconnected but your manual should specify. Without actually seeing what they are suggesting for mixture setting I can only agree with you. I set my idle mixture and idle speed the same way you describe. If you really have points then going through a good tune up, including replacing the points and plugs is a good idea before looking deeper into your other problems. Plugs do not last nearly so long with point style ignitions. You might make a note of how far off, if any, the timing is before you start though since that will help you decide if the tune up has a chance of fixing your running hot problem. You never answered, or I never saw it, do you use regular or premium? |
#7
posted to rec.boats
|
|||
|
|||
Base timing vs. ignition timing
On Jun 14, 9:49*am, "jamesgangnc" wrote:
"Robert M. Gary" wrote in ... Reading my shop manual for my 4.3L 190hp carb'd Merc I see that it describes setting the "base timing" as well as the "ignition timing". Both procedures look almost the same so what is the difference? Also, it says you must set the "Dwell" before timing the boat; what is that? The procedure for setting idle and mix on the carb is very complex in the manual. They say you have to be in the water to do it. In old cars I would just set the mix about one turn rich of when the car started to run rough and I'd set the idle based on the tach. Why can't you do the same on a boat? -Robert So you have confirmed that your boat has points? *The service manual only covers your model? Dwell is the point gap. *Truth is that a feeler gauge is accurate enough for setting the points. *There is considerable tolerance. *A timing light is the best way to set the time. *Make sure the boat is at the correct idle first. Few boats have a vacuum advance but in the cases where they do it is typical to set the idle with it disconnected but your manual should specify. Without actually seeing what they are suggesting for mixture setting I can only agree with you. *I set my idle mixture and idle speed the same way you describe. If you really have points then going through a good tune up, including replacing the points and plugs is a good idea before looking deeper into your other problems. *Plugs do not last nearly so long with point style ignitions. *You might make a note of how far off, if any, the timing is before you start though since that will help you decide if the tune up has a chance of fixing your running hot problem. You never answered, or I never saw it, do you use regular or premium? Actually, dwell is expressed as an angle, and it is the measurement of time the points or electronic module is in a closed state. |
#8
posted to rec.boats
|
|||
|
|||
Base timing vs. ignition timing
On Jun 14, 12:39*pm, Gene Kearns
wrote: On Sat, 14 Jun 2008 08:43:05 -0700 (PDT), penned the following well considered thoughts to the readers of rec.boats: On Jun 14, 9:49*am, "jamesgangnc" wrote: "Robert M. Gary" wrote in ... Reading my shop manual for my 4.3L 190hp carb'd Merc I see that it describes setting the "base timing" as well as the "ignition timing". Both procedures look almost the same so what is the difference? Also, it says you must set the "Dwell" before timing the boat; what is that? The procedure for setting idle and mix on the carb is very complex in the manual. They say you have to be in the water to do it. In old cars I would just set the mix about one turn rich of when the car started to run rough and I'd set the idle based on the tach. Why can't you do the same on a boat? -Robert So you have confirmed that your boat has points? *The service manual only covers your model? Dwell is the point gap. *Truth is that a feeler gauge is accurate enough for setting the points. *There is considerable tolerance. *A timing light is the best way to set the time. *Make sure the boat is at the correct idle first. Few boats have a vacuum advance but in the cases where they do it is typical to set the idle with it disconnected but your manual should specify. Without actually seeing what they are suggesting for mixture setting I can only agree with you. *I set my idle mixture and idle speed the same way you describe. If you really have points then going through a good tune up, including replacing the points and plugs is a good idea before looking deeper into your other problems. *Plugs do not last nearly so long with point style ignitions. *You might make a note of how far off, if any, the timing is before you start though since that will help you decide if the tune up has a chance of fixing your running hot problem. You never answered, or I never saw it, do you use regular or premium? Actually, dwell is expressed as an angle, and it is the measurement of time the points or electronic module is in a closed state. Dwell is accurately expressed in degrees..... but, point gap is a function of that angle and the "dwell angle" can be approximated in terms of point gap. (Distributors are always set by feeler gage before using a dwell meter.) I agree, although each (dwell angle, and point gap) can be altered independently of each other via hardware changes. Proper set-up of this particular distributor sounds like both a dwell meter and an advance timing light would be necessary, unless you have one of those old Snap-On distributor testing machines to set the distributor RPM, gage the dwell, and watch the curve as you apply vacuum and/or RPM. (And I am assuming some sort of vacuum or mechanical advance is part of the assembly.) I remember those! |
#10
posted to rec.boats
|
|||
|
|||
Base timing vs. ignition timing
"Gene Kearns" wrote in message ... On Sat, 14 Jun 2008 13:17:58 -0400, Jim penned the following well considered thoughts to the readers of rec.boats: "Gene Kearns" wrote in message . .. On Sat, 14 Jun 2008 08:43:05 -0700 (PDT), penned the following well considered thoughts to the readers of rec.boats: On Jun 14, 9:49 am, "jamesgangnc" wrote: "Robert M. Gary" wrote in ... Reading my shop manual for my 4.3L 190hp carb'd Merc I see that it describes setting the "base timing" as well as the "ignition timing". Both procedures look almost the same so what is the difference? Also, it says you must set the "Dwell" before timing the boat; what is that? The procedure for setting idle and mix on the carb is very complex in the manual. They say you have to be in the water to do it. In old cars I would just set the mix about one turn rich of when the car started to run rough and I'd set the idle based on the tach. Why can't you do the same on a boat? -Robert So you have confirmed that your boat has points? The service manual only covers your model? Dwell is the point gap. Truth is that a feeler gauge is accurate enough for setting the points. There is considerable tolerance. A timing light is the best way to set the time. Make sure the boat is at the correct idle first. Few boats have a vacuum advance but in the cases where they do it is typical to set the idle with it disconnected but your manual should specify. Without actually seeing what they are suggesting for mixture setting I can only agree with you. I set my idle mixture and idle speed the same way you describe. If you really have points then going through a good tune up, including replacing the points and plugs is a good idea before looking deeper into your other problems. Plugs do not last nearly so long with point style ignitions. You might make a note of how far off, if any, the timing is before you start though since that will help you decide if the tune up has a chance of fixing your running hot problem. You never answered, or I never saw it, do you use regular or premium? Actually, dwell is expressed as an angle, and it is the measurement of time the points or electronic module is in a closed state. Dwell is accurately expressed in degrees..... but, point gap is a function of that angle and the "dwell angle" can be approximated in terms of point gap. (Distributors are always set by feeler gage before using a dwell meter.) Proper set-up of this particular distributor sounds like both a dwell meter and an advance timing light would be necessary, unless you have one of those old Snap-On distributor testing machines to set the distributor RPM, gage the dwell, and watch the curve as you apply vacuum and/or RPM. (And I am assuming some sort of vacuum or mechanical advance is part of the assembly.) -- Grady-White Gulfstream, out of Oak Island, NC. Homepage http://pamandgene.idleplay.net/ Rec.boats at Lee Yeaton's Bayguide http://www.thebayguide.com/rec.boats --- avast! Antivirus: Outbound message clean. Virus Database (VPS): 080614-1, 06/14/2008 Tested on: 6/14/2008 12:40:10 PM avast! - copyright (c) 1988-2008 ALWIL Software. http://www.avast.com I just looked it up. All Carbed 4.3L Mercruisers use Thunderbolt ignitions. No Points to bother with. No mechanical advance to bother with. No timing to set other than base timing. That also means, then, I think..... that he has a Thunderbolt V ignition and one must ground the "advance wires" to bring the distributor into "base timing." If that isn't accomplished, the computer will continue to screw around with your attempts to properly set timing. Unfortunately, successful timing of this engine is dependent on a properly operating carb.... I'm confused as to why the OP's manual even refers to dwell, unless it isn't the right manual...... -- Grady-White Gulfstream, out of Oak Island, NC. Homepage http://pamandgene.idleplay.net/ Rec.boats at Lee Yeaton's Bayguide http://www.thebayguide.com/rec.boats --- avast! Antivirus: Outbound message clean. Virus Database (VPS): 080614-1, 06/14/2008 Tested on: 6/14/2008 6:11:13 PM avast! - copyright (c) 1988-2008 ALWIL Software. http://www.avast.com Seloc And Clymer are notorious for putting several models in the same model and not always giving proper reference when doing procedures. It's better to have the OEM manual for the engine you have. The OP could have a Thunderbolt 4 or 5 depending on year. If I recall as long as RPM was 550 to 600 the base timing could be read without grounding or shorting wires. |
Reply |
|
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
How to Adjust Timing on a Electronic Ignition | General | |||
Does altitude affect ignition timing? | General | |||
Suzuki ignition timing | General | |||
Worst possible timing | ASA | |||
Timing Question, Using a Timing light on an Old Outboard. | General |