Looper Bogs only when Hot

[Brew2]

1986 Evinrude 140 looper.

Been chasing a bogging problem for a looooong time. Carbs are clean (extremely clean), new carb kits, new fuel pump, new fuel lines, good spark and compression, no air leaks that I can find in the fuel system.

When the motor bogs you can get it to recover by bumping the primer.

Here is the part I'm not getting. When the motor is cold, it runs perfectly. Even when the motor has been running for a while, it still runs great as long as you don't shut it off. Shut it off after running it for a while, let it sit for a bit, restart, and it bogs when you accelerate.

Could the radiant heat from the motor that builds up when you shut it off be effecting something in the fuel system? Alternatively, could something be warping when hot, letting air in the fuel system, then return to normal once cooled?

Any thoughts appreciated as I've run out of ideas.

Thanks in advance.

Brew

 

[tashasdaddy]

Re: Looper Bogs only when Hot

pumping the primer, points to fuel delivery. are you using a fuel/water separator. it really sounds like a fuel restriction some where. maybe a clogged pick up in the tanks or clogged vent.

 

[okam]

Re: Looper Bogs only when Hot

Brew2, I have the same motor and have posted with your problem in the past. I had bogging and idle problems that I chased for years. I never could put a finger on the problem. I eventualy put a set of carbs and throttle bodies from a 1995 130, and changed t-stats with 1995 set up no water flow control on the throttle, the new setup uses the relief springs instead. The result was amazing, like throwing a switch, totally differant motor. Great idle, no hesitation, same top end. I should have done years ago, I must have chased that problem for 3 years. Good luck with yours, you might have a carb body that warps when it gets warm.

 

[Brew2]

Re: Looper Bogs only when Hot

Thanks guys.

I'll double check the vent and pickup tubes for clogs, although I'm not sure it would explain why the bog only happens when the motor is hot.

The warping carb body might explain things. I guess I could try and track down a set of carbs/throttle bodies like okam did. I wonder if as a test, I could try and seal the carb bodies to the throttle body with a gel of some sort. If the carb body was warping, maybe the gel would prevent an air leak.

I guess the other thing I could do would be to remove the cowling to let more heat escape and see what happens. If that solved the problem, at least I would know it has something to do with excess heat.

Appreciate your thoughts gentlemen.

Cheers,

Brew

 

[okam]

Re: Looper Bogs only when Hot

Brew, when the motor is warm and starting the problem spray spray around each carb when idling. I found that when sprayed around each carb you could hear a increase or decrease in rpms. I still have carb bodies and throttle bodies if you find that is your problem.

 

[Brew2]

Re: Looper Bogs only when Hot

Thanks Okam.....I'll give that a try. Won't be near the boat for a few weeks. Not even sure I'll have a chance to run it then as the resevoir I do my boating on is being drained off.....might not be any water left in a few weeks!!

I'll keep you posted and thanks again for the advice and support.

Cheers,

Brew