engine not running right

[tad7777]

i have a 1970 40 h.p. evinrune ,, it runs great for about 1 minute,then it seems like it loses power,about half power,then starts running good again back up to full power,,i noticed black burnt oilly stuff on the exhaust port,,the plugs was black,not to bad.is this a bad plug?? or coil?? or a carb problem?? thanks

 

[R.Johnson]

Re: engine not running right

Dropping to half power could be one of several reasons. I would do a running test on the ignition system, Ckeck fuel flow, restricted or air leak. Where the problem comes and goes makes it hard to second guess. Tell us what you have checked up to this point.

 

[rickdb1boat]

Re: engine not running right

And check fuel tank vent, also. Make sure it's clear or open.

 

[tad7777]

Re: engine not running right

i havnt checked anything yet,,it 7;30 am , first thing is checking the plugs, also one thing i did notice is the gasket on the tank lid cap is worn, ripped in half, missing a area, does it matter on this certain engine , if the cap is sealed?? tad

 

[Solittle]

Re: engine not running right

Your description fits fuel problems. Check for an air leak in the fuel supply system (lines, connectors, bulb) or crud in the carbs. A common problem is air leaks in the o rings of the connectors from the fuel line to tank or motor.<br /><br />A bad gasket in the fuel tank cap should not be part of the problem.

 

[tad7777]

Re: engine not running right

thanks everyone, I put new gas in the tank, put it in the water,, it runs good,, at high rpms sounds good running ,then down to lower rpm's like i throttled down ,,still seems to be smooth, just at lower rpm's then ,,races up to where it shound be ,, without me touching the throttle,, so i checked the plugs thought one was fouling , they are both good,,,,it must be a fuel problem, i am thinking the float is messing up,,since this has a old cork type, ,,please give me your opions thanks tad

 

[tad7777]

Re: engine not running right

a more clearer desciption,,, as i am traveling at around half throttle,this motor sounds like i throttled down ,without me touching the throttle,, it stills seems smooth,so i ruled out a plug fouling,,then it goes back up to where it should be,,the rpms,, without me touching the throttle,,,thanks again,, anyones help is appriciated,,tad

 

[rolmops]

Re: engine not running right

It sounds like interupted fuel supply.<br />The best thing to do is to check your fuel supply through trial and elimination.<br />Could there be dirt on your fuel filter??<br />Is there a pinhole in the hose?Does the bulb stay hard?Does it flatten because of vacuum?.Does it go soft?Is there dirt in your fuel pump?And so on.Check them all and use a manual to guide you.<br />good luck

 

[tad7777]

Re: engine not running right

i checked the tank,the hoses ,the bulb,it pumps up to a tight squeeze, it dont suck in when running, ,the filter is clean, ,i will look at the fuel pump next,,thanks tad

 

[rickdb1boat]

Re: engine not running right

Sounds like the float level is either set wrong or fuel saturated. Gets going across the lake, then dies down from lack of fuel in bowl. Reduced RPM's gives bowl a chance to re-fill and fills enough again to supply the engine with proper fuel amount causing the motor to pick back up again. Good theory, anyway. Then again, fuel pump might not be keeping up. Try this: Squeeze bulb when it dies down and if it picks RPM's right back up again, service fuel pump. If not, service Carb.

 

[Solittle]

Re: engine not running right

http://www.outboardrepairs.com/carburetors/