Loss of Power on '79 Evinrude

[MntkaFishin]

I took the boat out yesterday for the second time this spring and everything was running fine, good rpms, the boat would plane nicely, so I decided to shut things off and do some fishing for about an hour. When I started her back up I noticed that at full throttle the engine would almost bog down and the power just wasn't there(ie., the boat wouldn't plane and the rpm's weren't nearly as high). Being that I'm relatively new to boat motor maintenance and this is a rather old engine, 25 HP '79 Evinrude, I'm not sure were to start. One thing I did notice is that the motor would kind of shake, almost on que, every couple of seconds. Is there a couple of simple checks a newbie could do to try and isolate the issue? I would imagine it has something to do with either a bad plug or a compression issue.

[Valv]

As you mentioned I would check compression on motor, get 2 new plugs, and run a seafoam in your tank.

Read procedure on top of this page, let us know what are the reading with compression test, and we'll go from there.

[marine_man]

I'd also check for spark to make sure you didn't drop a power pack.

marine_man

[eyebjim]

Drain your fuel tank. I had a similar problem and it turned out to be water in the tank. It is at least an easy thing to try.

[dkf]

Yep could be water (Add water Remover, a bad or cracked coil, fouled plug. Make sure vent on tank is open. Look around the motor for any fuel leaks or even a clogged fuel filter. I run an inline filter on the hose.

[C.C. Waters]

I took the boat out yesterday for the second time this spring and everything was running fine, good rpms, the boat would plane nicely, so I decided to shut things off and do some fishing for about an hour. When I started her back up I noticed that at full throttle the engine would almost bog down and the power just wasn't there(ie., the boat wouldn't plane and the rpm's weren't nearly as high). Being that I'm relatively new to boat motor maintenance and this is a rather old engine, 25 HP '79 Evinrude, I'm not sure were to start. One thing I did notice is that the motor would kind of shake, almost on que, every couple of seconds. Is there a couple of simple checks a newbie could do to try and isolate the issue? I would imagine it has something to do with either a bad plug or a compression issue.

interesting.