Here's the rundown on my engine troubles, and the steps and advice from Don about what to do. At this point, I'm almost certain there's something with the carb - but for those who may have some sputtering/coughing issues (or need choke to run smooth, another issue I had), here are the steps I took to troubleshoot:
Anyway, the situation is thus on my Tartan 34C:
The engine had been running fine for approximately 25 hours of use over 2 months when, suddenly, it began coughing and sputtering - fortunately I was close to the dock and returned. Figuring it had been some time since a tune-up since I just purchased the boat, I purchased new points, condenser, rotor, spark plugs, and cap, and replaced them a couple weeks later.
The engine then ran fine again - except that to run smooth the choke was pulled perhaps half-way out. I had chosen to use the slighter hotter plugs from the original, so I thought perhaps that was related - and I was using 87 octane.
The engine then ran fine and smooth for approximately an hour - although the engine did sit for about 4 months after the tuneup while I was away before running for the hour - however, after the hour, I noticed that the temperature began to climb - reaching almost 170 - when I reduced the power to let the engine cool (traveling the intracoastal in Florida). At that point the engine began losing power, coughing, sputtering, and then quit about 15 minutes later, refusing to restart.
45 Minutes later, under tow, the engine started running fine again with the temperature at 135-140 and the choke all in the way in (no choke).
Returning to the dock, I replaced the water strainer (no temperature problems now), the fuel filter, the coil, the spark plug wires, and the points - again. When I initially replaced the coil (an MSD) everything ran fine for about 5 minutes and I thought "Ah hah!" but shortly after the sputtering began again - then I replaced the points and plug wires, which had no noticeable effect.
The engine still coughs and sputters, although occasionally for short periods it will run smooth but almost always when cool. It's acting almost as if someone, when not under load or under load, is *rapidly* turning the ignition key off and on - it's most noticeable under load. When warm, it now seems to run most smooth with the choke all the way in, although it still coughs and sputters. There isn't any preignition and I don't think it's a timing issue..
I had thought about fuel contamination, but the RACOR 200FG filter is brand new. The only additive I put in was Marvel Mystery Oil.
Do you have any additional suggestions? I tried tapping the carb float bowl to see if it was sticking and that was inconclusive. I have the mechanical fuel pump, and I have seen no fuel leaks, since the tank is higher than the engine. My current thought is to check the connection at the ignition key, and perhaps hit that was some WD40 or something similar if it's corroded.
Oh, whenever the engine starts to *really* die (as if the key was off longer and usually occurs at idle), it can be recovered by pumping throttle twice - which then returns it to a slightly coughing, sputtering, but mostly running state.
Any suggestions would be greatly appreciated - this sort of intermittent but consistent problem drives me nuts and I'm at a wit's end what else to check.
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After reading the forums, I tried additional items:
Thanks to your wonderful forums, the idea of jumping from the solenoid to the positive side of the coil was tried this morning before I went to work - have to accomplish the important things .
However, it had no effect. One other thing I tried: With the key in "On" and the motor not running, I manually opened the points to see if it would spark - and it did quite nicely.
This morning when I tried to run it, there was no improvement - it still sputtered even when cold. I also turned off the fuel valve at the tank, let the engine run until it ran out of gas, opened the valve, and in about 3 cranks the engine sputtered to live - so the pump must be working as well.
Any other ideas? My last guess now is a carberator problem of some kind, although tapping it to see if the float valve was sticking didn't seem to help either. And, unfortunately for me, my carb skills are probably my worst engine skills.
---
Don's Response (I hope you don't mind me sharing):
If the problem remains, I’d check the short black lead between the negative terminal of the coil and the points. Sometimes the point in the wire that slips under the distributor cap will break.
There is also the issue of the time or two when you needed to have the choke partially engaged to keep the engine running smoothly. This condition is almost always caused by a small piece of dirt trying to move through the main jet. If the requirement to choke the engine returns, I recommend that you disassemble the carburetor for cleaning, or at least the main jet. The main jet can be removed by removing the 1/2” hex-headed main passage plug below the float chamber.
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I'll update everyone when I take apart the carb, although in all honesty I really don't know what I'm doing with carbs. Anyone have any "gotchas" or sage advice on dealing with the carb let me know. I'll try just removing the main jet first - clean it - and replace it and hope all is well. I'll let yah'll know what I find, although the main jet removal will be fun enough since it's smashed against a bulkhead and not easy to get to on the Tartan.
-Chas
Anyway, the situation is thus on my Tartan 34C:
The engine had been running fine for approximately 25 hours of use over 2 months when, suddenly, it began coughing and sputtering - fortunately I was close to the dock and returned. Figuring it had been some time since a tune-up since I just purchased the boat, I purchased new points, condenser, rotor, spark plugs, and cap, and replaced them a couple weeks later.
The engine then ran fine again - except that to run smooth the choke was pulled perhaps half-way out. I had chosen to use the slighter hotter plugs from the original, so I thought perhaps that was related - and I was using 87 octane.
The engine then ran fine and smooth for approximately an hour - although the engine did sit for about 4 months after the tuneup while I was away before running for the hour - however, after the hour, I noticed that the temperature began to climb - reaching almost 170 - when I reduced the power to let the engine cool (traveling the intracoastal in Florida). At that point the engine began losing power, coughing, sputtering, and then quit about 15 minutes later, refusing to restart.
45 Minutes later, under tow, the engine started running fine again with the temperature at 135-140 and the choke all in the way in (no choke).
Returning to the dock, I replaced the water strainer (no temperature problems now), the fuel filter, the coil, the spark plug wires, and the points - again. When I initially replaced the coil (an MSD) everything ran fine for about 5 minutes and I thought "Ah hah!" but shortly after the sputtering began again - then I replaced the points and plug wires, which had no noticeable effect.
The engine still coughs and sputters, although occasionally for short periods it will run smooth but almost always when cool. It's acting almost as if someone, when not under load or under load, is *rapidly* turning the ignition key off and on - it's most noticeable under load. When warm, it now seems to run most smooth with the choke all the way in, although it still coughs and sputters. There isn't any preignition and I don't think it's a timing issue..
I had thought about fuel contamination, but the RACOR 200FG filter is brand new. The only additive I put in was Marvel Mystery Oil.
Do you have any additional suggestions? I tried tapping the carb float bowl to see if it was sticking and that was inconclusive. I have the mechanical fuel pump, and I have seen no fuel leaks, since the tank is higher than the engine. My current thought is to check the connection at the ignition key, and perhaps hit that was some WD40 or something similar if it's corroded.
Oh, whenever the engine starts to *really* die (as if the key was off longer and usually occurs at idle), it can be recovered by pumping throttle twice - which then returns it to a slightly coughing, sputtering, but mostly running state.
Any suggestions would be greatly appreciated - this sort of intermittent but consistent problem drives me nuts and I'm at a wit's end what else to check.
--------
After reading the forums, I tried additional items:
Thanks to your wonderful forums, the idea of jumping from the solenoid to the positive side of the coil was tried this morning before I went to work - have to accomplish the important things .
However, it had no effect. One other thing I tried: With the key in "On" and the motor not running, I manually opened the points to see if it would spark - and it did quite nicely.
This morning when I tried to run it, there was no improvement - it still sputtered even when cold. I also turned off the fuel valve at the tank, let the engine run until it ran out of gas, opened the valve, and in about 3 cranks the engine sputtered to live - so the pump must be working as well.
Any other ideas? My last guess now is a carberator problem of some kind, although tapping it to see if the float valve was sticking didn't seem to help either. And, unfortunately for me, my carb skills are probably my worst engine skills.
---
Don's Response (I hope you don't mind me sharing):
If the problem remains, I’d check the short black lead between the negative terminal of the coil and the points. Sometimes the point in the wire that slips under the distributor cap will break.
There is also the issue of the time or two when you needed to have the choke partially engaged to keep the engine running smoothly. This condition is almost always caused by a small piece of dirt trying to move through the main jet. If the requirement to choke the engine returns, I recommend that you disassemble the carburetor for cleaning, or at least the main jet. The main jet can be removed by removing the 1/2” hex-headed main passage plug below the float chamber.
--------
I'll update everyone when I take apart the carb, although in all honesty I really don't know what I'm doing with carbs. Anyone have any "gotchas" or sage advice on dealing with the carb let me know. I'll try just removing the main jet first - clean it - and replace it and hope all is well. I'll let yah'll know what I find, although the main jet removal will be fun enough since it's smashed against a bulkhead and not easy to get to on the Tartan.
-Chas
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