'71 Evinrude 25 HP loses power at WOT

[STeveZ]

It seems to run fine at lower speeds even up to 3/4 throttle, but if you open it up it will run for a few minutes and then lose power.

Stall out is generally avoided by backing off, shifting to neutral and revving before shifting back into gear and accelerating.

Today it continued to run w/o stalling but the RPM's fluxuated wildly.

Again, I can get it up to WOT, but this behavior follows.

Tried Gumout and DryGas w/ little effect. Popped the top in hopes of finding a filter or glass bowl to clean/replace but none was immediately recognizable.

I'm thinking this sounds like the fuel supply, but why just at wide open?

 

[JUSTINTIME]

Re: '71 Evinrude 25 HP loses power at WOT

try connecting it to a 5 gallon portable tank
if the problems go away then u know its fuel

 

[STeveZ]

Re: '71 Evinrude 25 HP loses power at WOT

Thanks for your input, I have two five gallon tanks on the boat. I got the same behavior w/ both batches of fuel, one of which is new from the pump.

 

[fireman57]

Re: '71 Evinrude 25 HP loses power at WOT

When it does this have a buddy with a timing light check for spark to make sure that you are not losing spark to one cylinder. You probably need to clean your carb as it sounds like you have stuff in the jets. Disassemble and soak in a good carb cleaner then blow all the passages out well with compressed air.

 

[Captain Caveman]

Re: '71 Evinrude 25 HP loses power at WOT

Is it getting enough air? I know there have been one or two times that I forgot to open up the air valves on my portable gas tanks. It would run fine at low speeds but then lose power after a minute at WOT.

 

[clemsonfor]

Re: '71 Evinrude 25 HP loses power at WOT

Like said many times for others, pump the primer bulb to see if it runs stronger/faster when pumping. May be a restriction, bad bulb or something. May also be time for a tune up, points and condensor.

just some thoughts

-nate

 

[soodchay]

Re: '71 Evinrude 25 HP loses power at WOT

I had the same problem with my seahorse, it reves up fine and when its left on wot it spits and sputters. I tracked it down to lose big end bearing slop causing the point to responed incorrectly so i fixed it with an aftermarket elect. breaker point kit and now it works fine.

 

[tashasdaddy]

Re: '71 Evinrude 25 HP loses power at WOT

it sounds like fuel supply, air leak in fuel line, clogged filter, fuel pump not keeping up, clogged vent on fuel tank, bad gasket between fuel pump and block, hole in diaphram, dirty jets in carborator.

pull the spark plugs, right after it shuts down, see what they look like, wet or dry. you need to find the cause, if it is fuel restriction, it is also lube restriction.