engine issue

Engines, Drive trains, Propellers, Steering, Ground Tackle and other mechanical system
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moosemcclintock
Posts: 81
Joined: Tue Jun 28, 2011 8:09 am

engine issue

Post by moosemcclintock »

I've been having troubles with my 6 hp Yanmar on my F25. Turns out I had water in the fuel (a lot, not sure how it got there) as well as some algae growing. We pumped out the fuel, chunks of gunk came out as well as a lot of water, swabbed the inside of the tank as well as we could and got more goop out, refilled the tank partly with injector and fuel treatment, changed out the filters for the water separator and fuel. Engine starts fine, and runs OK for about 10 minutes, then starts losing power when under load (in gear and around 2800 rpm, engine dies to about 2200 rpm). I back off the throttle, it goes right back to full power for a few minutes, then loses power again. Over and over. I let it idle at 1800 rpm for 2 hours to make sure the new fuel had bled out all the old stuff, plus bled the injector several times. Does this sound like air in the system? And if so, any idea where it would be coming from ? Or is there something in the injector?

jdpandlp
Posts: 65
Joined: Mon Dec 08, 2008 8:59 am

Re: engine issue

Post by jdpandlp »

Had the same conditions on a yanmar 4jhe, starvation under load. Turned out to be a restriction in the fuel line between the tank and fuel filter. Specifically there was crude at the point the barb for the flexible fuel line threads into the fuel pick-up at the tank. There is a significant difference between the id of the pick up and the id of the hose barb. Good luck

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moosemcclintock
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Joined: Tue Jun 28, 2011 8:09 am

Re: engine issue

Post by moosemcclintock »

That sounds about right, with the engine under load and begging for more diesel, can't quite get it, slows down to the level where it can get enough fuel to stay powered, run it slower and the line fills back up, then starves again. How did you get the crud out of the fuel line?

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Rick Simonds
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Joined: Fri Dec 05, 2008 8:49 pm
Location: Tallahassee, FL

Re: engine issue

Post by Rick Simonds »

Check, too, the fuel tank pickup tube. Many boats originally came with a screen at the bottom of the pickup tube inside the tank. Just pull that screen out, if there's one there. It just gets clogged. The filter(s) will take care of anything the screen would have caught.
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jdpandlp
Posts: 65
Joined: Mon Dec 08, 2008 8:59 am

Re: engine issue

Post by jdpandlp »

Very low tech. The hose barb was the first fitting in the fuel line starting from the tank end. When I saw the crude I dug it out with a piece of wire. I then opened the Racor filter and used compressed air from a can like is used to clean computer keyboards to blow the line out. What I took out of mine was lint and small threads and aluminum shavings. Best guess is they came from installing the new pick-up for the generator when it was installed a few years earlier. It has been fine since.

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moosemcclintock
Posts: 81
Joined: Tue Jun 28, 2011 8:09 am

Re: engine issue

Post by moosemcclintock »

Well, I blew the hoses out and let it run for a while, basically was revving up and down on it's from 1000 to 1800 rpm's. Shut it down and blew the hoses out again (there were three), ran it again at about 1800 to 2000 rpm, then it slowly cranked up on it's own again and ended up at 2800 rpm and stayed there for about 10 minutes so I think it's OK for now. I can't get at the fitting on the tank, was this the area that was clogged in your fuel line?

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