Engine Performance Down. Mystery?

[Jacoburn1304]

I have a 2006 Mercury Opti-Max 115 hp 2-stroke attached to 21' deck boat Princecraft that has been running rather erratically. It ran great all summer and then the last time out before the end of the season it started having issues. It appears it can't run above 20 mph and while there are no issues I can hear from the captain's chair, it appears to lose torque at a certain point which won't allow it to get over 20. Its not over revving or anything, its really just like its hitting a governor or something and it keeps the engine from continuing to climb.

To try and avoid an expensive repair man, I changed the fuel filter, new spark plug, ran new gas through it to flush everything. Also, I talked with a prop specialist, and he doesn't think that's the issue, plus there is no significant damage to the prop when I look at it.

Any thoughts, suggestions? If it isn't something I can repair on my own, I'd like to at least know the right kinds of questions to ask my mechanic. And if anyone is in the Lake of the Ozark area, I'll take suggestions for a good local mechanic.

Thanks Ya'll.

 

[Chris1956]

Take a compression test and put a timing light on each spark plug lead to make sure all are firing. If the compression is low, or not all cylinders are firing, you have your issue. If not, it may require an Optimax expert to find the issue.

 

[bruceb58]

My engine was having a similar issue last year, Turns out my thermostat was stuck open. Besides the power loss, I was getting water in my crankcase which you of course won't get.