Outboard dies when hot

[sailorboy1]

My 9.8HP outboard has developed a problem dying when slowing down to idle after it has gotten warmed up. Before slowing down it will have been running just fine. It is definitely a fuel related problem. The fuel itself is good as it is all ethanol free and has gone through a Mr Funnel before gong into the outboard tank (this is a separate tank) and I have so far gotten it restarted on the same tank fuel. It always seems that if I let the outboard cool down some I can get it started again.

Could it be getting vapor locked somehow?

Other things to try to check.

I am in Bahamas and for the most part have no access to anything fancy to try.

[GreenWave]

could be a fuel pump issue. If you pump the bulb while it is running in idle does it run longer?

[Jammer]

Common and typically caused by a clogged low-speed jet or circuit in the carburetor.


Try applying some choke as the engine slows down and if that makes the problem less bad then that would tend to confirm it's the low speed jet.


Solution is complete disassembly of the carb followed by an overnight soak in a bucket of 2-Butoxyethanol, then some careful work with a toothbrush and compressed air. Wear rubber gloves, but the 2-Butoxyethanol isn't nearly as toxic as the old time carb cleaners that were methylene chloride based.


2-Butoxyethanol is available in convenient short-filled gallon paint cans with a little strainer included for around $50 at most auto parts places, which sell it as carb cleaner. It is also sold by Interlux as their brushing reducer 2333N, so use that if you already have a can of it in your paint locker.

[sailorboy1]

Thing is it first happened 2 weeks ago. I drained and changed the gas and it ran fine and at the time thought it might be the gas tank vent and started just loosening the cap. Then it happened again yesterday at end of a 2.5 mile dinghy ride. I wouldn't think a carb problem would have gotten better for 2 weeks. But it does seem to get over it with a little choke.

But I don't know.

[Jammer]

If loosening the cap helped then maybe your fuel pump is shot or there's an air leak in the fuel line. Can also try the primer bulb and see if that helps, would indicate a bad fuel pump/fuel line if it does. No primer bulb then hold the gas tank above the engine.

[GreenWave]

Just to add to what I wrote earlier and what Jammer just said... air leak ended being my problem with my outboard recently. The connection between the tank and fuel line was leaking. I bought a new connector for the tank and ended up changing out the fuel line/bulb. I was having issues at idle and it was hard to get the bulb to prime.

[sailorboy1]

Originally Posted by GreenWave

Just to add to what I wrote earlier and what Jammer just said... air leak ended being my problem with my outboard recently. The connection between the tank and fuel line was leaking. I bought a new connector for the tank and ended up changing out the fuel line/bulb. I was having issues at idle and it was hard to get the bulb to prime.

Yes I have read of this as problem. Of course changing this out isn't as easy as it sounds when there are not places to buy new stuff.

[sailorboy1]

Well it dies now if I try to idle without the choke. Starts right up with choke and fast speed. Have taken carb about twice now, guess will have to try and soak it.

[rslifkin]

Have you tried squeezing the primer bulb when it's about to die? If that helps, I'd suspect a weak fuel pump or a restricted fuel line and the pump just can't move enough fuel at low RPM.

[Chris Cringle]

Is it a two or four stroke? If it is a two stroke, a rare but very real problem is that the two halves of the crankcase could have a slight separation at the seam that is air tight when the engine is cold but widens when the engine warms up (or gets hot) and expands. The opening allows air to be pulled into the engine which dilutes (leans) the air/fuel mixture and stalls the engine. When the engine contracts, the engine will run again until it heats up again. To check for and, if present, locate such a crack, spray WD-40 along the crankcase seam just as the engine starts to fade. If there is an air leak, the engine willl rev- up rather than stall. Seal the seam with J-B Weld.

[sailorboy1]

Originally Posted by rslifkin

Have you tried squeezing the primer bulb when it's about to die? If that helps, I'd suspect a weak fuel pump or a restricted fuel line and the pump just can't move enough fuel at low RPM.

tried that, didn't help

Back out to pull the carb off again

[GreenWave]

Sounds like your idle speed jet is plugged. Find a very fine wire to ream that out once you take it apart.

[sailorboy1]

3rd time is the charm and now it is running great! Shining a light up the idle jet there was "something" needing removal.

That is my theory and I currently am sticking with it!

[sailorboy1]

incredible weight leaves your shoulders as an anchor out cruiser when the dingy outboard runs

[Jammer]

Glad it worked out. I feel your pain. I've pulled carbs off and missed stuff before too, sometimes more than once. When parts are available and inexpensive it's tempting to join the disposable movement and just replace it.