Today my wife and i took our boat out finally this year for a test run. Its a 1984 14ft fiberglass with a 35hp evinrude. The control box is omc. Well, today we were running around on lake lewisville running some gas through the carb and i stopped to adjust the carb to get the idle smooth. All of a sudden the control box started making a buzzing sound. It only made the sound when i turned the key to start it. My wife googled it on her phone and it said it could be that the engine is overheating, but i didnt think an engine that old had a sensor that detected that. Does anyone have a clue what the buzzing sound could be??? It buzzed all the way back to the dock. I tied it up and let it sit for about 10 minutes and when i went to start it to put it on the trailer, wouldn't you know, no buzzing! Any help would be greatly appreciated!

I'm pretty sure that is what it is. I have one in mine. Was it peeing water good

yeah it was peeing ok, but it didnt seem to pee good when it was just idling. im gonna change out the impeller to be safe. how does the control box know when the motor is running hot? especially on a 1984 model.

an 84 isnt that old for a marine engine, there is still a sensor in the head, should be pretty easy to spot, it will look like a wire going directly into the head but there will be a small rubber grommet around it.

Hope this helps, FISH ON!

yeah, im pretty sure now that it was the overheat sensor. im guessing my thermostat was sticking. it was peeing, but that doesnt mean that the stat was opening. i pray i didnt mess up the head on it. im gonna take it apart and change the thermostat and gaskets. probably gonna do a compression test to make sure its still ok.

well i pulled the head cover off to get to the thermostat. it is gross. stat looks nasty and the gasket was horrible. im ordering a new thermostat kit tomorrow. i went ahead and pulled the head to see what the pistons looked like. i dont have a clue what they should look like. what would they look like if they are fried? the lower cylinder looked alittle rusty(not that bad), and the top cylinder looked ok i guess. on the inside of the head there was a black resin that was built up alittle on one side. the head gasket looks fine, but im gonna order another one of those too. what is a good method to get the old gasket funk off and clean the head up good?

Take a picture of the rust you referred to and post it here. ( using photobucket, or some other hosting service.)

As for the head gasket...you HAVE to install another one now. If you dont know the head bolt tightening pattern or proper torque, go buy a service manual NOW before you torque down that head. To remove the old gasket, gently scrape it off with a pocket knife, but DO NOT nick or dent the gasket surface at all.
Go slow and take your time. This is not a job that can be rushed. Do the same for the engine side of the surface too. ( stuff a rag in the cylinders to keep junk from falling inside)
Dont leave 1 single piece of old gasket material behind Get it all...and wipe it clean. DO NOT SAND it off, either !

I dont know if that engine has any water diverters under that head or not...and if so....replace them too. ( Mike will know).

RE: Fried: turn the flywheel by hand and look at the cylinders. Any scoring, scratches..or what appears to be melted aluminum on the inside? Or are the smooth and pretty? ( wipe the oil out).

The black resin on the head is carbon build up. Take a little seafoam and rinse it off. If that doesnt work...put the spark plug in it, turn it upside down and pour seafoam or carb cleaner in it and let it soak a while.

I want to know more about that rust. There should NOT be rust in a cylinder. That's an indication of a blown head gasket or cracked sleeve or block. Show is pics of the rust.

Thanks oldfrog. I will try and get pics up if i can. I thought it might be rust, but now that i think about it, i dont think it was. It was more like carbon build up. It just had a brownish color. I didnt think about turning the flywheel(brain fart). I will do that when i get home. Im gonna order a new thermostat w/washer, spring, plate cover gasket, head gasket. I just hate waiting for them to come in! I want them now! haha!

I turned the flywheel yesterday to see how the pistons looked. They seemed ok. No scars on the cylinder walls and no rust anywhere. The walls looked smooth. I stuffed them with towels to keep junk out until i get the parts in. Thanks for all the help. If any of you have any additional advice, please do tell!