70 hp evinrude running strange?!

[kcwhunter]

Have a 77 evinrude 70 hp 3 cyl that has had problems for two seasons now. The engine will start but will not rev up in neutral. Out of water with the muffs it will rev right up?! Also after a short trip through a no wake zone it will not take the gas. The throttle just doesn't want to respond. Back off and slowly accelerate and it will then take off half decent. It has also shuddered while trying to accelerate. I rebuilt the fuel pump last year and the boat ran alot better but still can't idle it up when in the water!? HELP?!?!?!?!!? NEW MEMBER LOVE YOUR FORUMS

 

[jtexas]

Re: 70 hp evinrude running strange?!

Welcome to iboats!

Out of the water you have no back pressure on the exhaust so it sounds fine...but it can't run with a load on it.

I'd do a spark test and compression test first just to rule those out. Note the appearance of the spark plugs. And make sure the timer base isn't sticking. Fuel line holding pressure?

Otherwise, sounds like carb rebuild time.

 

[KYHunter2]

Re: 70 hp evinrude running strange?!

Welcome.

What your motor does on muffs , has very little to do with on water performance.

There's no load on the motor.

Even a poor running motor sounds decent on muffs.

I'd rebuild carbs, check entire fuel system .

Do a complete tune-up, including spark test .

Also be sure your running the proper champion plugs. L77J4 gapped at .040.

As well as timing, link and sync. ( required after carb rebuild anyway).

KYHunter

 

[kcwhunter]

Re: 70 hp evinrude running strange?!

Thanks for the quick replies! The fuel line is holding pressure and the plugs are burning nice. I'm leaning towards rebuilding the carbs. Is it really necessary to get it to a dealer to have the carbs synced? Thanks again for the quick relpies, nice forum.
Kcwhunter

 

[kcwhunter]

Re: 70 hp evinrude running strange?!

Oh almost forgot where is the timer base located/look like, and if it is sticking what do I do to free it?
Kcwhunter

 

[xtraham]

Re: 70 hp evinrude running strange?!

the air box on those engines over time, can pinch of the bottom carb fuel line (drove me nuts) i cut awat the box for clearence, replace the hoses w/new ones and make sure those carbs are clean, when you are sure they are clean, clean them some more..check the coils for cracks too

 

[KYHunter2]

Re: 70 hp evinrude running strange?!

Its under the flywheel the wiring and stop for advance is on the starboard side.

When you advance the throttle the timing advance moves as well.

There;s a adjustable stop with a small black rubber piece on the end.

Used during link and sync. to set advance, ( Timing ).


KYHunter

 

[jtexas]

Re: 70 hp evinrude running strange?!

you can link & sync...shop manual = really great investment...got mine at marineengine.com