Runs great for 5-10 minutes...then trouble

[stlhdr2]

I have an 82 Evinrude 35 HP outboard that runs great for 5-10 minutes under a load (high RPM & Low RPM), then it will bog down and run at a very low idle. Won't die, but it won't power up like it should. If I turn the motor off and let it set for a bit I can start it up and drive off...for 5-10 minutes. Then the process repeats. It's getting fuel, the carb has been rebuilt. Seems like electrical but was hoping someone might have an idea of where/what to look at. I was thinking the power pack might be the cause???? Any help would be appreciated.

 

[Gary H NC]

Re: Runs great for 5-10 minutes...then trouble

Any signs of cracks on the coils?
I would start with a spark test when its acting up.
Then hook a portable fuel tank up with fresh fuel and test to rule out a fuel system problem from bad gas or dirty tank,fuel pick up ect..

 

[tashasdaddy]

Re: Runs great for 5-10 minutes...then trouble

99% bad coil heating up and failing. then it cools down and works till warm.

 

[stlhdr2]

Re: Runs great for 5-10 minutes...then trouble

Thanks for the responses,

I'm assuming you mean the ignition coils when you mention the coil? I have tested both of them and the resistance is within specs for both the primary and secondary windings. Can the ignition coil/s still be my problem?

 

[1730V]

Re: Runs great for 5-10 minutes...then trouble

Thanks for the responses,

I'm assuming you mean the ignition coils when you mention the coil? I have tested both of them and the resistance is within specs for both the primary and secondary windings. Can the ignition coil/s still be my problem?

Yes and yes. Coils can behave differently when warmed up.

There is a simple, sometimes effective, test.

1. Run the engine in a barrel until it gets good and warm.

2. Blow a hair dryer on the coils and see if you get a reaction.

 

[stlhdr2]

Re: Runs great for 5-10 minutes...then trouble

Thank you all for your help. It turned out that the power pack was the problem. I decided to bet against the odds and order a power pack and ignition coils for $100.00 rather than have the engine in the shop for $80.00 an hour. I plugged in the new power pack and was up and running. It appeared to me that the problem was electrical since it ran so well for a limited amount of time, then when allowed to cool off it would resume running for the same amount of time before acting up.

Again, thank you for taking the time to help out a novice!!