Fuel leaking from carb when primer squeezed

[Chris A]

Hi there.

Took the sib for a cruise yesterday, outboard is a 97 yamaha 25 hp 2 st

Cruised around for 20 minutes at around half throttle and the OB just died, noticed the fuel hose un-clipped, must have not clipped it in properly. Anyways, reconnected and could not get it to start. Noticed the primer bulb did not get hard and fuel leaking from the top of the carb, take it that's the carb vent?

Anchored up and let it stand for a bit, kept on trying to start it (did not fancy getting the oars out many attempts later the bulb hardened and managed to start it. Went back into sheltered waters and switched the OB on and off a few times and all was fine. Ended up running smoothly for the rest of the day with no further issues. Started it up this morning to flush through with muffs and all is fine.

What went wrong? Had a quick read on google and understand it could be the float / needle not seating.

Does this need further inspection or could the fuel hose un clipping and running out of fuel at half throttle have caused it? I always un-plug the hose at the end and let it run dry but not at high refs...

OB had a service recently, don't know if they would have inspected/serviced that?

Also if this does happened again while afloat, what's the procedure for getting it going again, think I was just lucky...

Thanks

[jwatson]

Whip the float bowl of the bottom off the carb and have a nosey too see if any thing is amiss

[doggypaddle]

As it cleared itself probably dirt in the carby.
I would get the carb stripped and cleaned out maybe replace the float and needle valve if nescessary. replace fuel filter and hose from filter to carby in case the internal face of the hose is flaking rubber .

[Peter_C]

Originally Posted by doggypaddle

As it cleared itself probably dirt in the carby.
I would get the carb stripped and cleaned out maybe replace the float and needle valve if nescessary. replace fuel filter and hose from filter to carby in case the internal face of the hose is flaking rubber .

Agreed! With everything.

[Chris A]

Hi guys, sorry for the delayed reply, been away...

I had the outboard out again last Saturday and she was running fine, later during the day she idled fine but struggled to idle straight from starting. (engine was warm at this point) Once underway its fine, even on idle. At one point it died on me, restarted then it cuts out after a few refs, almost like being starved of fuel? I used a spanner and lightly tapped the carb, top one? It then started and was running fine so called it a day, suspecting its the float needle etc...

Armed with some tools today I took the carbs off, hope I dont have spare parts putting it back, haha.

I have attached a few pics below, any feedback greatly appreciated as I am not sure what I am looking at or to look for.

This is the bottom carb with float bowl removed?



The float and needles from both carbs/floats? They seem fine to me and dont think theres a blockage as far as I can tell.





This is the inside of the float bowl? there seems to be a build up of shit/salt etc take it it should be clean?



this is the top with plate and seal removed, also some build up?



Does the needles look fine? do I just clean everything and re-assemble? I read about adjusting the float level but does not appear if one can do it with mine? the top carb/float bowl looks a lot cleaner than the bottom one.

Also since its all off now where and how do I look for the fuel jets to make sure they are clean, I am comfortable with tools but just zero knowledge with engines etc so willing to learn but dont have a parts list/service manual.

Just a bit more info, since last service a month ago I got new fuel tank, fuel line and primer bulb, they also fitted a second inline fuel filter between existing fuel filter and carb and have been using fresh fuel, so doubt and rubbish is coming from my part...

[Peter_C]

Not sure what kind of fuel filter they put on, but I would recommend a full size one that looks like an oil filter to remove water also.

All it takes is a tiny piece of debris. Those carbs need to be well cleaned. There was water or something that caused much of the corrosion. Rebuilds are necessary every 8+ years no matter what. Just depends on use and storage.

What is the thing the arrow points to, as it sure looks like a piece of debris.

[jwatson]

Mine has just come back from being serviced. Technician said to clean my tank and fuel lines out. When it struggles to idle, try pumping the priming bulb. If this helps then I would also investigate fuel pump.

[Chris A]

Thanks for the replies chaps.

Peter, that thing you see where your arrow points to is the choke plate / throttle plate or whatever you call the flappy disk thing. That's in the fully closed position. I was going to ask about that as the top carb the plate closes so not to cover the 3 tiny holes? I'm at work now but will take some more pics tomorrow to illustrate it better.

Let me start from the beginning. The OB was standing for a few years and did not want to idle, fine with a bit of throttle on the muffs. I took it in for a full service before using it. The guy said he had to strip the carb and clean it but still did not want to idle. He then re did the carb but then noticed the reeds? Where corroded and cleaned them. He said all was fine then.

Took it home and fired her up, idled perfectly, pulled the fuel hose and let her run dry. Typical British weather meant it stood for two weeks before I could take it out for a spin. Idle issues from the start, but again running fine with throttle. So took it back, he cleaned the carbs again and said there were debri in it. For peace of mind I bought a new fuel line, bubble and tank and they fitted a second inline fuel filter.

Took it out following week and all was fine, running perfectly as far as I am aware. Third time out it died under power and could not prime the bulb. Fuel coming through the top carb vent, managed to start it and all was fine for the rest of the day, and then I started this thread. Fourth time out all perfect from the start till near the end of the day as per previous post.

If the carb where stripped should that amount of build up be in there? I have used fresh fuel every time. Probably did about 4 hours in actual running time since last service. So doubt there's contamination from my side.

I'll get some more pics tomorrow, thanks.

[jwatson]

Are the floats punctured?

[Chris A]

Originally Posted by jwatson

Are the floats punctured?

No, they are fine...

[jwatson]

Check the pump

[Chris A]

I will open it tomorrow and have a look. Anything in particular I have to look for in the pump?

Thanks.

[jwatson]

On my old yam 40 it was a split diaphragm, which caused intermittent fuelling before it completely gave up. Be VERY careful when you open it, there's a spring that will pop out and remember how it goes back together! Also the gasket on mine tore easily but made a new one from cardboard & was fine.

[Chris A]

jwatson, I opened the fuel pump, all seems fine, no splits etc... no spring in there tho, its the type that attaches to the carb.

A few more pictures and questions.

Peter C pointed out what looked like a piece of debris. As explained its the throttle plate (if thats what you call it) thats in the fully closed position. This seems strange as the other carb it closes fully. pics below.

Top carb in closed position - closes fully.



Bottom carb in fully closed position, theres a slight gap, should this be like this and if not in what position should it be, I noticed you turn the little screw on the side to adjust it.



I also pulled the plugs out, they are new but seems very dirty with particles on it, is that carbon? seems like some oil leaking from the top one. Also with them pulled out looking into the cylinder it appears theres a lot of the black build up inside the cylinder. Does anything here need attention and what does the plugs say in their state?



Where the plugs go in, cant see on the pic but seems very dirty inside looking in with a light.



Regards.
Chris.

[Peter_C]

When looking at spark plugs look at the center white part. They should be a nice tan color and yours are.

The carbs butterfly will not create a 100% seal and that is okay. It lets the air in that the motor needs to idle.

Time to blow all the passages out really well, then put it back together.

At this point if it is an older motor, I would just replace the fuel pump. Cheap insurance, and no fuel leaks from reusing a gasket.

[jwatson]

Those plugs look like mine did before servicing. Oily.

[mattsleep]

Those carbs need synchronising together! And what oil ratio are you using?

[jwatson]

Seafoam could help you out. Clean those plugs & give it a blast then check again.

[Chris A]

Thanks for the replies guys...

Mattsleep - its autolube so no pre-mix.

Put all back together, no spare parts so all went back as it should. Started very easy and no choke required. Engine seems to have a much higher idle now, adjusted it a little on the idle screws but think the throttle needs slight adjustment too as theres not a huge difference in the low idle setting on the marking from below start to slow idle position.

Off to Loch Lomond in the morning to give it a good blast up and down the lake. Will report back.

[jwatson]

I'd be tempted to try premix 50:1 and disconnect the automix for the day. Those plugs looked v oily.