120 V4 Evinrude '93 - bogs down above 2000rpm

[Henry Francis]

The motor will not rev beyond 2000rpm under load. Have checked all 4 carbs(spotless) and replaced plugs, and checked fuel flow to VRO/fuel pump. At full throttle if I keep the ignition key depressed the motor will run at full revs - indicating a starvation problem. Can anybody give me some advise please?

 

[JB]

Re: 120 V4 Evinrude '93 - bogs down above 2000rpm

Jambo, Chambo.<br /><br />Have you checked fuel flow from the fuel pump? Are you sure all 4 cylinders are firing?<br /><br />Pull each plug wire when at idle. Does each cause a drop in rpm? Do all 4 plugs look the same?<br /><br />Your symptoms are those of an engine running on 2 or 3 cylinders due to a clogged carb jet.<br /><br />Let us know what you find.<br /><br />Good luck.

 

[dpminc]

Re: 120 V4 Evinrude '93 - bogs down above 2000rpm

Check for anything that would be activating the S.L.O.W. (Speed Limiting Overheat Warning) This can be any number of actual overheating causes, and can also be caused by a short to ground on any of the tan wires coming from the overheat sensors on the heads. Also, a bad power pack can trigger this to come on. The S.L.O.W. system limits engine speed to 2000 rpm in the event of an engine overheat. I beleive ther is also a blocking diode in the harness that has somting to do with this system, but maybe someone else can chime in on weather or not this is applicable to your engine.

 

[Brew]

Re: 120 V4 Evinrude '93 - bogs down above 2000rpm

I'm with JB on this one. I had virtually the same problem last summer. Turned out to be a partial/intermitent blockage of one of my high speed jets resulting in one cylinder not firing all the time.<br /><br />Good luck.

 

[Henry Francis]

Re: 120 V4 Evinrude '93 - bogs down above 2000rpm

Thanks for the advise.<br />After consulting the shop manual last night (of course did not have it with me at the lake this weekend) I discovered that I missed the high speed jets when I stripped the carbs. Our fuel in this part of the world is terrible, and just about all our problems here are fuel system related - it also does not help that we often do not use our boats more than 1 weekend a month.<br />Once again thanks and will come back if the next step fails.