1991 evinrude 40 hp top speed problem

[biggkahoona]

idles fine, trolls fine, but at full throttle it sarts o die after about 30 seconds, you have to constantly pump the fuel line ball to keep it going. the ball seems to hold pressure fine. is this a fuel line problem or carb or comppression??? please help

Thanks,

JB

 

[Rick.]

Re: 1991 evinrude 40 hp top speed problem

It's your fuel delivery. It's not getting enough for high speed. Pumping the bulb is taking the place of the fuel pump. Best of luck. Rick.

 

[kenmyfam]

Re: 1991 evinrude 40 hp top speed problem

Check,
Air leaks in the fuel system
Fuel pump delivery.

Welcome to iboats.

 

[stratman56]

Re: 1991 evinrude 40 hp top speed problem

JB - I am going through the same thing with an 80's 40hp. Runs great 1/2 throttle, when I open it up, starves for fuel. If I pump the bulb it runs good. If I dont, it will run out of gas.

If I back off the throttle, it seems ok.

When it starts to die, the bulb feels empty. The tank and line are garage sale specials, I wonder if there is an issue there.

Would have to believe if the motor runs, there is crankcase pulses that will operate the pump. I do not see any fuel leaking which would indicate maybe air getting in the line. I am going to locate another tank and fuel line and see if that is the issue....

 

[tashasdaddy]

Re: 1991 evinrude 40 hp top speed problem

bulb should not be hard once the fuel pump starts pumping.

is the vent open on the fuel tank?

99% you have clogged high speed jets in the carbs.

if the bulb is collasping (going flat) the vent is not open, or the pick up tube in the tank is clogged. remove bulb and blow air back into the tank to clear pickup.

 

[stratman56]

Re: 1991 evinrude 40 hp top speed problem

I reckon it is a fixed jet, if I remember correctly, we shimmed the jet with washers to adjust it.....mine does act like it is running a tad lean.

 

[stratman56]

Re: 1991 evinrude 40 hp top speed problem

Well -

I got mine running perfect just a bit ago.

What did I do? I started by checking the tank and line. The tank fittings seemed airtight, so it must be past that. The valve in the bulb seemed to allow fuel to run back to the tank, but it pumped ok so I left it be.

The connector at the engine was kinda haggard, seemed to leak air a bit when fitted to the male connector, so I replaced it.

Now I was up to the fuel pump and carb. The pump seemed to be ok, but I took it apart anyway, flipped the valves over just in case.

Put it back on with some gasket goop.

Took the carb apart, cant remember why I thought the drain plug was the jet. All looked ok, ran wire thru stuff to make sure, blew out with airgun. I noticed there was not much travel in the float, so I bent it down just a tad to let the bowl fill up a bit more.

Put it all back together, put in test garbage can, fired it up. Had the 'i'm too lean' hiccups bad. Backed out the idle asjustment, still seemed lean. Put finger over the throat, it calmed down. Hmmm....getting air somewhere. Checked all the little hoses, all seemed ok. The one going to the rev limiter seemed loose, I eliminated it.

Bingo! Nice idle....

Took it out to the ramp, go out to the river, opened it up - Yayus !! Now we are talking! Now it runs great !!!!

Not sure which did the trick, but the end result is good !!