20 Hp Outboard basketcase

Much help is needed here. I have a 1984 johnson outboard tiller that just won't quit acting up. Many mechanics have looked a the problem but cannot solve. New reeds, new fuel lines and bulbs, new fuel fittings, new fuel tank etc. THe engine runs ok for a half minute or so while cruising and then starts
to sumble and will stall. If I pump the bulb it will run better for a a half minute again. The mechnic put a new and larger fuel pump ( said the other was too small) but now the problem is worse. Any ideas? Compression is good too.

 

You're sucking air , probably at the filter.

Heavy grease may seal the offending leak long enough to find it.

Maybe an out of grove 0 ring.

Look also at the 0 ring at the end of the fuel hose , these cost almost nothing and cause hassles if nicked.

FAST FRED

 

Fast Fred,

Thanks for the advice. Do you mean the o-ring that is in the fitting goin into the fuel tank? If so I also tried several new fuel lines and we also " hard piped" the fuel line in the motor. Air is a good call. I will check over it again to see if I can find a leak.

 

You may be loosing compression in the crankcase. The compression also runs the fuel pump, therefore a bigger one would increase the problem.

 

I think that is the way this is turning out. It is compression no t vacuum that runs the pump right?

 

Yes, the piston creates compression in the downstroke. The pump has a diafragm that moves with it.

 

I think Gonzo's got it right. Has the engine sat for a long time? I've seen quite often in an engine that sits too long, the top crankshaft seal will dry out, and suck air or blow out the seal, causing the problems you mentioned.

 

The engine only sat for one winter. It worked fine and then just started acting up. Will a compression test identify the low compression. Is there another test I can do. We can't seem to figure it out. Are the seals you speak of difficult to install?

Thanks

 

A "low tech" way to test is to run the engine, and spray WD40 under the flywheel and listen for any change in rpm, sputtering, etc... The seal should be changed out by a good outboard mech. You need a special puller to remove the flywheel.