'83 V4 115hp WOT issue.

[Pete's Colorado Lund]

Just purchased my first real boat (had a canoe before) and have been working on it and fishing with it with some mishaps and success. It is a 1984 Lund Tyee 5.5 with a '83 Evinrude 115hp, and a '88 Evinrude 20hp. someday I would like to re-power the boat, but right now I am trying to get the motors fixed up. My question is about the 115hp. After getting rid of the old gas and running a can of OMC tune up according to the instructions, replacing fuel lines due to a leak, and replacing one of the four ignition coils I have a pretty good running motor. The issue now is that the motor will stumble or bog down a little at wot after a bit. It is not real big (a couple hundred rpm) and will never die. I would like to find out what is going on and fix it. My thought was that the fuel pump was having problems, but I am wondering what you guys think? Thanks!

 

[1983 ercoa 21']

Have you pulled the carbs and cleaned them ?

 

[Pete's Colorado Lund]

I haven't yet. Sounds like a good thing to try. Rebuild as well as clean?

 

[emdsapmgr]

A weak fuel pump will not pump enough fuel into the carb bowls to sustain WOT operation. Sounds like that might be your problem. To test this theory, have a buddy constantly prime the fuel hose bulb at WOT. If the engine runs great at WOT as long as he constantly primes the fuel hose bulb, you have a fuel delivery problem. That can include a weak fuel pump or some type of fuel restriction.

 

[Pete's Colorado Lund]

I did think to try the fuel bulb to see if it fixed the rpm drop and it was not clear - it may have helped a bit, but not enough to cure it. Both of you are thinking that I should stay focused on the fuel system as the site of the problem which I find reassuring. However, is there anything in the ignition system that could cause a rpm drop at wot (especially after it has warmed up)? Thanks.

 

[emdsapmgr]

Weak ignition components tend to fail once the engine heats up to normal operating temps. You've got a lot of expensive ignition parts which could be failing: stator, timer base and two power packs. The coils are usually pretty reliable. [If you have a problem with one, you can always swap it out with another for testing.] Always good to test for spark on all 4 plugwires when: 1. the engine is warmed up 2. When it's under load (in forward gear in the lake) 3. The cyl-drop test is good, as is the spark-gap test.

 

[1983 ercoa 21']

Agree with post #6