2005 115 Johnson PLSOR dies off idle

[Harkonnen]

More trouble with the project. Took it out again. After about 15 minute WOT run and maybe 30 minutes of fishing, start again. Starts easily, but if I give it gas, dies quickly. Or may die while idling for no obvious reason; almost feels like it is fuel starved. Pumping the primer bulb does not help.

Got it coaxed to life, made back to the dock OK. Behaved well on the run, but same problems during idle/off idle cropped up. No other obvious symptoms, except white spittle in carb throats (below; may or may not be related).

Wild guesses, roughly in the order of likelihood:

Water in the fuel
Fuel line blockage
Pump about to go out
Insufficient pulse to drive fuel pump at idle

Other things I might be overlooking, and how do I test for those?

Advice greatly appreciated. Thanks!

 

[Chris1956]

Those motors tend to do that. Some think it is heat soak.

The work around is to run them at high idle in neutral until they start to run clean. They should then behave normally, until you shut them off, and restart them after 30 minutes..

You might test your thermostats. I have a theory that the motor is slightly overheating, causing the issue.

 

[racerone]

If pumping the primer bulb does not help , there is nothing wrong with the engine fuel pump !!!---The white stuff is normal.

 

[Harkonnen]

Those motors tend to do that. Some think it is heat soak.

The work around is to run them at high idle in neutral until they start to run clean. They should then behave normally, until you shut them off, and restart them after 30 minutes..

You might test your thermostats. I have a theory that the motor is slightly overheating, causing the issue.

Thermostats/springs are new. It's been sitting for 5 hours now; just tried again, same thing.

 

[tphoyt]

To check for water in the fuel disconnect the fuel line and pump some fuel into a glass jar with the bulb.
Let it settle out for a few minutes. If there is water you will see it in the bottom of the jar.

 

[racerone]

Have you tried adjusting low speed mixture needles ?---Are carburetor bowls warped ?----Throttle bodies ( calibration pockets ) cleaned?

 

[Harkonnen]

Have you tried adjusting low speed mixture needles ?---Are carburetor bowls warped ?----Throttle bodies ( calibration pockets ) cleaned?

No, ran normal before. No, replaced for that reason. How do I clean those?

 

[racerone]

Have to ask.----You replaced the carburetor bowls ?----Swapped carburetor jets to the new bowls?

 

[Harkonnen]

Have to ask.----You replaced the carburetor bowls ?----Swapped carburetor jets to the new bowls?

I believe, yes. Those came as a part of carb kit, IIRC.

 

[Harkonnen]

Have to ask.----You replaced the carburetor bowls ?----Swapped carburetor jets to the new bowls?

Previous one was a lousy turn of a phrase. Yes, replaced bowls last December or so. Did carb kit at the same time. New jets came with the kit, IIRC.

 

[Chris1956]

New jets and the bowl plugs do not usually come with the new bowls or carb kits. usually you get gaskets and inlet needles and seat. Sometimes floats.

However, if you did not swap the main jets over to the new bowls, the motor would run real rich.

Your carbs may have an intermediate orifice. Those can clog, and are located on the throttle bodies. I would blast them out with carb cleaner.

Also, on a lot of those carbs, the idle needle is covered by a gasket and plate on the throttle bodies. The cover can be removed, the jet/needle/passages can be sprayed clean with the carb cleaner, and a new gasket and the cover reinstalled. One does not need to remove the idle needle to clean it.

 

[Harkonnen]

Have to resurrect the thread, now that I got time to mess with the motor again. So after I seemed to have fixed the float issues (discussed way back when on this forum), the motor was running normal for a while: no smoke, no exhaust drip. And then this problem started, and looks like I got it backwards the first time around: it seems to be running rich. Some smoke at idle, and when you close the throttle from about 1500 rpm, a big puff comes out. What am I missing now? What could have made the engine run rich all of a sudden?

Thanks!

 

[Chris1956]

Floats adjusted too high can cause carb to flood, especially when you come off throttle. How does it accelerate?

Do you have the main jets installed in the new carb bowls?

 

[Harkonnen]

Floats adjusted too high can cause carb to flood, especially when you come off throttle. How does it accelerate?

Do you have the main jets installed in the new carb bowls?

Lousy. When it does not die coming off idle, that is.

I cannot really answer the question about the jets (have to go back and see what was in the kit), but I don't think it's the jets or the floats: it was running right, until suddenly it wasn't. Could it be enricher circuit?