1999 75HP Force - Blown Powerhead Gasket?

What are the symptoms of a blown powerhead gasket on these motors?

I got the boat about 4 months ago. The guy that had it before me only had it for a couple of months (I've got the paperwork where he bought it) and due to health issues (older gentleman) could not climb up and down the decks easily and wanted a pontoon instead. The guy before him had repowered with a 1999 Force 75HP.

The guy I got it from said it had a "miss" to the engine and thought it was trash in a carb or something. I got a good deal and turned him onto a pontoon.

Boat ran fine except it did have a little skip. I changed the plugs (replaced with what was already in it) and changed the primer and quick connect on the fuel line. The engine perked up and we ran it several times all day with no problems. Compression test showed 148psi on all 3 cylinders and all 3 are firing.

One day I ran it about 30 minutes out and stopped to fish. It would not restart. Spin the engine over for a couple of minutes (that's a looooong time) and it would finally start and run like crap for 10-20 minutes and finally clear up and run like nothing was wrong.

Discovered the fuel filter was empty when this was happening. Replaced the primer again (could hear gas flow back to tank when bulb was turned on it's end) and also found a bad diaphragm and gasket in the fuel pump. Rebuilt the fuel pump.

Ran the boat another trip and same old story, run for a while, stop and fish and it would not restart.

Fuel filter was again empty. Removed quick connect from engine, spin engine over for a minute to dump any fuel inside the carbs or cylinders and reconnected fuel line and it restarted after being primed. I did this several times and each time this would "fix" the problem or at least get me back to the ramp.

I knew I had some downtime, so I dropped it off at a marina. He replaced the thermostat, plugs and quick connect on the tank. He said the QC was wrong (it was) and the plugs were not the correct plugs for the motor. He also said the motor was running hot (this had NEVER been an issue) and water tested.

I put it on the water that day (Sept 15) and it ran great until about 6pm. I had to use the trolling motor to get back to the ramp. The boat finally started back up and ran fine.

Took the boat out Sunday Sept 18 and it ran fine. I fished off and on until after lunch and it would not start. I pulled the QC, spun the motor and reconnected and it started. It ran fine for a minute or two and the overheat alarm went off. I shut it down. After sitting for about 30 minutes I restarted and it ran fine.

Rode for about 15 minutes and the alarm went off again for a few seconds (long enough for me to turn around to look at the pee stream) and the alarm stopped. Ran another 10 minutes or so and overheated again. Shut it down. Trolled for a few hours and got ready to leave and nostart. Remove QC, pin motor, reconnect, jump on top of the water and hit the ramp with no more problems.

Had the boat sitting in the marina driveway in Alabama when they opened on Monday morning. I had to leave it and get back to Atl for a meeting.

Talked to the owner later that afternoon and he said the carbs already had new kits in them and everything was properly adjusted. Checked the floats and the needle & seats, everything looked fine. Then he noticed the powerhead gasket was blown "and should have picked up on that the last time it was there because it was a very common problem." He said that it looked like it had been leaking for a long time and he could see where water was coming out of it and some of the bolts in the area were rusted.

Now...

I've never worked on 2 stroke engines but was a dealer tech for many years on everything from cars to heavy equipment. I know how to fix a 4 stroke engine and how they work, but know very little about 2 strokes.

I've got a bad, bad feeling about this. Part of me think I'm paying for crap that is not broke (I tested the thermostat that he took out 50 times and it never stuck with me).

From my limited research, it looks like the powerhead gasket is the gasket on the bottom of the powerhead. What is this thing sealing up? Could it cause an overheating condition or the conditions that I have described?

Usually I don't let others work on my own vehicles, but we have been busy with work and my mother had a heart attack and triple bypass during all of this. Between trying to take care of her and catching up work I have not had time to do much with this boat.

I just have a bad feeling about it. I plan on heading over tomorrow and having a come to Jesus about it. I just want to know what I'm talking about before I get there.

PS. I always mix my oil and gas at 50:1 and add green Stabil and an ounce of Seafoam per gallon of gas. I have no clue what was used it in before I got it.

It just runs to darn good when it's running good for there to be anything major wrong with it.

I am not a mechanic, but I had an 86 90hp merc that did some of the same stuff except it would just flat cut off going down the lake. I am not 100% sure what exactly was wrong with it I think it was something with the power head and/or bearings. We got a new won and did not rebuild the old one. Hope I am wrong, but it sounds just like what our motor was doing, and the mechanic that works on our stuff is a full time boat mechanic who is very good and shoots straight with you (he doesn't screw you). Again I am far from a mechanic though