Small Engine Mechanic

Hey guys, looking for a small engine mechanic who could take a look at my boat motor for me. It is a 92' model Onan Performer on a longtail go-devil frame. It has been surging all of a sudden and i cant seem to pinpoint the issue. I have already taken carb off and cleaned real good, bought new gaskets and rebuilt. After reassembling, i cranked it up and ran like it should. Made a fishing trip this past weekend everything was good till i cranked up to head back to the launch. Soon as i started the motor it ran like normal then would start surging..... bog down, rev up, bog down, etc.....I am somewhat mechanically inclined but this has me beating my head against the wall.:banghead.....NEED HELP!!!!!

Built in tank or remote with bulb? I would start checking line from carb back for pinch,air leak or internal blockage.

I have an external 6 gal tank with bulb. Before I broke into the carb I changed all fuel fitting to straight in-line brass barb fittings. Still used same hose I originally had, maybe I can replace the hose and bulb. I don't have anyway of measuring vacuum pressure on motor.

Have you tried pumping bulb while it's surging like that? Not familiar with the onan motor but assuming it has a fuel pump. Find it and check the pulse line from pump to the block, it could be plugged,cracked or loose. If that appears to be ok, pull line and check it and the port at block for carbon build up or anything that might be obstructing it.

Ethenal gas can cause all of the above probs, plus it can cause the probs if it is not fresh especially with the weather we have been having. Good luck!
Alfred

Yes, I have primed the bulb while engine is surging but when I do I don't see any gas filling up fuel filter. It just gets real tight. Yes it has a fuel pump, the vacuum diaphragm type.

You have a restriction some where between bulb and filter housing then. Hose could be coming apart inside. Take hose loose from fitting and pump bulb. If fuel comes out ok pull any fittings and line from filter back to connection and make sure they are clear also remove filter and check for flow through housing. could have a peice of trash in filter housing.

I do notice that when the motor is running looking at the fuel filter, very little fuel is being sucked into the filter from pump. Could this be a fuel pump issue? Also the hose that runs to the crank case, what does that do, create a vacuum pressure?

I had a similar problem a while back, motor would bog down then pick up and run fine for a minute then bog again, it turned out to be the pick up line inside the fuel tank, ethanol had ate it up, new tank fixed the problem

When piston goes up and down it pulls a vacume and releases thus creating the push pull to activate the internal part of the pump.

I checked the pick up line in gas tank, seems to be fine. Didnt see any debris in the screen at the tip of it. So far i have the exhaust off (which is really bad off so rusted up it has holes everywhere anyone know where i can get one made), top part of carb off soaking with some SeaFoam Deep Creep. Took off plug where main jet is and drained the bowl. Float doesnt seem to be hanging up on anything, but i did find some brown crap at bottom near main jet. dabbed it up with a q-tip for right now. Thats as far as i got today, will continue to remove little by little each day. Saturday I plan on going get new fuel hose and bulb. Sucks no one works on these motors anymore, I called one small engine place and as soon as i mentioned Onan he said nope. All i wanted them to do was listen to my problem and give me a direction. Oh well, service manual and knowledge/advice from yall really covering all bases. Thanks for help, I sure hope I can get back to normal.....them fish and frogs are calling my name.

The lines may be collapsing and causing the fuel to flow too slowly. The Erving is probably the engine running lean. Then getting fuel and bogging because its too much fuel. Then it begins a cycle of too rich- too lean and so on. Once it's off you prime it. Crank it ant run till it pulls the fuel line shut then it starts the cycle again. Either way it can't hurt to change the fuel line and bulb to some ethanol resistant ones.

You guys are smart

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Originally Posted by jkcckc2002

the lines may be collapsing and causing the fuel to flow too slowly. The erving is probably the engine running lean. Then getting fuel and bogging because its too much fuel. Then it begins a cycle of too rich- too lean and so on. Once it's off you prime it. Crank it ant run till it pulls the fuel line shut then it starts the cycle again. Either way it can't hurt to change the fuel line and bulb to some ethanol resistant ones.

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x-10

Hookem if you really run into parts problems the closest Cummings dealer should be able to help you. They own,sell and service Onan. Also a good RV dealer might be able to help. Tons of those Onan generators in RV's.

Yea, I order all my parts from Cummins MidSouth in Morgan City. I have had to change out the flywheel ring and a few other things. Now when yall say " lines may be collapsing" are yall referring to fuel lines?? Like the inner layer could be torn and stops flow. I guess I could give Millers RV a holler and see if they could take a peek at it if I cant get it running right after the weekend.

Please explain what you mean by Erving...

End result......Went to West Marine Saturday morning and picked up some new fuel hose and primer bulb. Pulled out all old hose, from carb back to gas tank. Used compressed air to clean out lower part of carb and all orifices, then cleaned top part. Put all back together and she runs fine. Let her run for about 30 mins in driveway to burn out all the carb cleaner and deep creep that was used. Thanks for all the tips fellas...

good news.....happy for you......

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Originally Posted by Hookem3

End result......Went to West Marine Saturday morning and picked up some new fuel hose and primer bulb. Pulled out all old hose, from carb back to gas tank. Used compressed air to clean out lower part of carb and all orifices, then cleaned top part. Put all back together and she runs fine. Let her run for about 30 mins in driveway to burn out all the carb cleaner and deep creep that was used. Thanks for all the tips fellas...

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glad "we' could help:Rofl

Vet, you've done fixed another one.
"gene"

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Originally Posted by fishervet

You guys are smart

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Years of tearing up my dads stuff and not being able to afford to pay someone to fix it. That and a good military education.