40hp Mercury Force-Smoking at higher speed

I have an old Mercury force that seems to run okay at low speeds, but when I accelerate to higher speeds it smokes and a the throttle has some alarm that sounds. I don't know much about boats, this is my first one. I have heard it could be the impeller, but not sure. I wanted to get an idea before I take it in to get ripped off because I don't know anything.

Re: 40hp Mercury Force-Smoking at higher speed

That could be the overheat alarm. There is what some people call a pee hole on the bottom/back part of the engine housing ( for lack of a better term).When the engine is in the water and running there should be a stream of water coming out, Might need to be a little warmed up if theres a thermostate. This is what keeps your engine running at operating temps. you could seize up your engine running it when its overheating. Hopefully you didnt do any damage already. If there is not water coming out it could very well be your impeller and not knowing the condition of the thermostate might be wise to just change that as well. Also the pee hole tube could be clogged with some debris, I have had mud dabber wasp clog mine up before with mud or whatever they use. I would say on average your looking at $70-$85 per hour for labor. Impellers are fairly easy to change if you know what your doing. Thermostats are easy however i had my housing bolts break off in the eng block. When i repaired that problem i used anti-seize on the new bolts.

Re: 40hp Mercury Force-Smoking at higher speed

Thanks.