25hp losing power at WOT

Cox

Seaman
Joined
Sep 19, 2008
Messages
65
Just got back from a week long fishing trip. My 25hp Evinrude (1996) motor was working just fine for the first 4 1/2 days. Mid afternoon of day 5, we took off and hit WOT for about 100 yards when all of the sudden the motor lost power and dropped us back to about 1/2 throttle. It stayed like that for the rest of the afternoon. I couldn't even get the motor to try to get to full throttle.

First check: fuel. Fine...even replaced the fuel line from the tank to motor to be sure (even though we'd tried priming the bulb while underway and it made no difference). Then, checked spark. I disconnected one of the two spark plugs and tried starting the motor, no problem fired right up. Then I hooked it back up and disconnected #2. Engine wouldn't fire. I figured I had a bad spark plug so off I went to Eagle River to buy two new plugs (along with the new fuel line), figured I might as well replace them both well I was at it.

Got back and switched everything out....new line/bulb/connectors, new plugs. Started up the motor, pulled away from the dock, and got underway....boom, worked like a charm. I got to WOT in no time, boat up on plane and moving just like it always has. Got about 2 or 3 hundred yards from the dock feeling great that I'd fixed the issue and we could fish the last couple days of the trip without issue. Started to make my turn to head back and BAM....same issue resurfaced.

A year or two ago, I had a similar issue where the boat would start surging under load at WOT and at the time I replaced the Fuel Pump and everything was fine. The difference this time is that once she bogs down and loses power, I can't even get it to try to get back to WOT. It's like the best it can do is 1/2 throttle and that's it. My brother-in-law and I limped around the lake from spot to spot, letting the trolling motor take over once we got to spots. Every now and then, while underway (Sloooowwwly) it would try to fire for a second but would quickly give up.

My first thought was fuel pump so I ordered a new one already (got home from trip late last night) but then I realized that I hadn't actually tried to restart the motor again while isolating the spark plugs. I put it in a test tank just a bit ago and found that once again, even with new plugs, it would only start when one of the two cylinders were in action. The other one wouldn't turn it. So I just ordered a new Coil thinking maybe that's the culprit.
I realize there are many threads on this topic but all in slight variations from what I've experienced over the past few days. If anyone has any thoughts, opinions, experiences, suggestions, etc...I'd appreciate hearing what you have to say.

There are plenty of minor details/checks that I've performed and probably left out but I'll clarify as we go along. It's been a long week and my head isn't exactly "in the game" as much as it could be right now.

Thanks in advance for any feedback, this forum has always proven to be a wealth of knowledge and has saved me hundreds of dollars in diagnosing issues!

Todd
 

Daviet

Fleet Admiral
Joined
Sep 24, 2008
Messages
8,958
Re: 25hp losing power at WOT

Couple of thoughts. You need to check the spark with an air gap tester, the spark needs to jump a 7/16" air gap and be bright blue. If you don't have proper spark on one cylinder try swapping the plug wires from top coil to bottom coil and see if #2 is still dead. If the problem moves, you have a bad plug wire. If that makes no difference, swap the complete coil assy and see if the problem moves to #1, if so you have a bad coil. If neither one of those trails helps, go to the CDI website and locate your engine. Use their trouble shooting guide to help you find your no spark problem.
 

boobie

Supreme Mariner
Joined
Nov 5, 2009
Messages
20,826
Re: 25hp losing power at WOT

Eagle River where?? As a guess I'd say you have a bad power pack.
 

Cox

Seaman
Joined
Sep 19, 2008
Messages
65
Re: 25hp losing power at WOT

We were actually in Phelps, Wi on Lac Vieux Desert for the week. Eagle River just happened to be the closest town to get what I needed on short notice.

Daviet...thank you for the suggestion. I'll give that a try after work and see if there is a difference.

Thanks!
 

OptsyEagle

Lieutenant
Joined
Sep 13, 2006
Messages
1,365
Re: 25hp losing power at WOT

The other possibility is that you are fouling one of your spark plugs. Are you using Champion QL77JC4 plugs? You should definitely check your spark with an external spark tester and ensure both are firing a 7/16" gap.
 

boobie

Supreme Mariner
Joined
Nov 5, 2009
Messages
20,826
Re: 25hp losing power at WOT

Small world. I orginally came from Woodruff.
 

Cox

Seaman
Joined
Sep 19, 2008
Messages
65
Re: 25hp losing power at WOT

I believe I found the source of the problem. The wire from the Power Pack to the Ignition Coil was frayed a bit and intermittently working. I'm waiting on parts but after I replace it I will post the result.
 
Top