115 Evinrude looses power when hot

[Pat Crowley]

I have recently bought a 115 Evinrude, about mid 80's I think, and the previous owner told me that when it ran at WOT for a few minutes, the motor would slow down drastically as if it were not getting enough gas. For some reason he had the head gaskets changed (He didn't say if they found evidence of leakage or not.) and tried the motor again. It ran good for an hour or so but on the way home at WOT it once again started to slow down. He sold the motor to me and bought himself a new one. I'm not an expert mechanic but that doesn't sound like power head problems to me. More like gas tank, lines, fuel pump, carbs, etc. or (unlikely but possible) power pac getting hot and partially going bad or some other crazy ignition problem. Oh yeah, forgot to mention that when the motor started to slow down, he would let off the gas for a few seconds or so until it started running right again and it would run at WOT for a while then slow down again. Said the could run at 4000 RPM all day with no problems. Thanks for any help or suggestions on what to check. I plan to put it on my boat soon but will rebuild the carbs and fuel pump before doing so.

 

[emdsapmgr]

Re: 115 Evinrude looses power when hot

You may have a weak fuel pump. It may not be able to provide enough fuel for sustained high rpm opereation, but will run all day at 4000. If this is a mid 80's unit, it should have a combination fuel/oil pump. Not an inexpensive part. You can test for a weak pump by having someone constantly prime the fuel hose bulb when the engine tries to run over 4000. The constant priming will force extra fuel around the pump, directly into the carbs. If it runs sustained high rpm's while doing this, probably a weak pump. Since the engine is new to you, there are some basic things you may want to do to establish a point of maintenance reference: a compression check, spark check, visually inspect the cyls by looking inside the spark plug holes. Renting a laser temp gun at a local auto parts store will establish how warm the engine/heads get when running at idle and full throttle. Installing a new water pump impeller will insure your ownership starts out right.