Outboard Carb problems

[Solent sailer]

This is very likely to be caused by the ethanol content in modern gasoline which deposits a residue inside the carburettor. For small engines, and therefore small carburettors with small diameter jets this causes blockages. I have an outboard motor and also a vintage motorcycle and it is a constant problem. The only successful solution is to buy yourself an ultrasonic bath, which do not "blast" but gently agitate. They are quite inexpensive (circa £40), and in relation to the time you will otherwise spend without one in cleaning, assembling and then testing it is a bargain. Use the bespoke carburettor cleaning fluid and de-ionised water and make sure the physical size of the bath is sufficiently large enough for your carburettor. I generally find that about five to ten hours is enough to clean all the residue out of the carburettor.

Then for next year, only use premium grade gasoline, which has 5% ethanol, rather than the cheaper grade of fuel which has 10%.

We got a ultra sonic tank from ebay/amazon years ago great on the carb, but also watch straps, rings, the fine filter on the derv pre filter. Well worth getting one even if you don't need it on the carb again! Also when not using the outboard much try the long life petrol you can get from many farm suppliers or chain saw suppliers no ethanol and 3~5 year shelf life its about twice the price but shouldn't go off in the carb.

 

[Spirit (of Glenans)]

We got a ultra sonic tank from ebay/amazon years ago great on the carb, but also watch straps, rings, the fine filter on the derv pre filter. Well worth getting one even if you don't need it on the carb again! Also when not using the outboard much try the long life petrol you can get from many farm suppliers or chain saw suppliers no ethanol and 3~5 year shelf life its about twice the price but shouldn't go off in the carb.

"Aspen"

 

[lustyd]

I had a similar sounding problem and it turned out that the internals of the hose were getting bunged up. I think it was from a deposit building up inside the hose itself, which I found when trying to replace the priming bulb.

I had a similar problem. Turned out to be the valves in the priming bulb which was a very cheap and quick fix to replace the bulb.

I wouldn't believe all the superstitious nonsense about modern fuel, it's been in use for a very long time elsewhere but for some reason people make up stories about fuel going stale instead of maintaining their engines. Cars, bikes and boats the world over operate just fine on old fuel left in tanks sometimes for decades.

 

[Jobs a good un]

If you can, try connecting up to a different fuel tank, and different hose.

I had a similar sounding problem and it turned out that the internals of the hose were getting bunged up. I think it was from a deposit building up inside the hose itself, which I found when trying to replace the priming bulb.

Not a Tohatsu, a 2 stroke 2 cylinder Mercury 6 hp.

Hi James
I noticed yesterday when running engine if we turned the tank on its side the stuttering seemed to stop , then we turned it the right way up there was a hiss of air from the tank , also when starting the engine the primer on fuel lead wouldnt go hard is the tank the problem ?

 

[lustyd]

If the bulb doesn't harden then it's likely your valves are broken and you need a new bulb since pressure must be getting released back into the tank (or you're somehow pumping fuel into the internal tank). You may also have an issue with your breather on the tank if air hisses in, check and possibly clean the breather.

 

[James_Calvert]

Hi James
I noticed yesterday when running engine if we turned the tank on its side the stuttering seemed to stop , then we turned it the right way up there was a hiss of air from the tank , also when starting the engine the primer on fuel lead wouldnt go hard is the tank the problem ?

Your tank might have a problem. There will be an internal hose picking up the fuel from the bottom of the tank, could that be dislodged or in some other way defective?

Maybe the hiss was because the breather couldn't work properly when the tank was on its side? Dunno, just theorising!

A second tank can be quite handy anyway, if you can't borrow one with the right connection for your motor.

 

[Refueler]

Hi James
I noticed yesterday when running engine if we turned the tank on its side the stuttering seemed to stop , then we turned it the right way up there was a hiss of air from the tank , also when starting the engine the primer on fuel lead wouldnt go hard is the tank the problem ?

Sounds like you have a faulty pick-up tube in the tank ....

If the tube has a small hole or leak - then fuel delivery will be irregular .. the priming bulb will be getting a mix of air and fuel - so will not go 'hard' ...

Some tanks - the fuel line is connected to a pick-up that is mounted via a plastic plate screwed / riveted to the tank top. I have a couple of tanks like that and one old tank that pick-up tube is welded to tank top !!

You may be able to unmount pick-up tube to check its internal condition.