Overheating Gamefisher 15HP

[oldhorse]

I am new to this forum and appreciate the opportunity to get help with a very perplexing overheating problem that just developed on my Gamefisher 15HP motor. It is a 1989, model #225.581501 manufactured by Force Outboards.
On my last fall fishing trip it started to overheat. About every other time I started it, it would run normally but on every start I had to watch for water flow out the port since it would start smoking and get blazing hot very quickly. After the first episode of this I tightened the head bolts and was afraid I had warped the head but the following day it had great compression when it was running normally.
To date, I have replaced the water pump but that did not solve the problem. Although I have visited sites which seem to indicate there is a thermostat, the parts breakdown in the owners manual does not show one and I have not seen one in dissembling the lower leg to replace the pump. At this point I plan to dissemble it again and run compressed air and perhaps a jet of water up the water intake tube to see if there is anything lodged in the intake. Beyond that it would appear I need to remove the head unit (trying to avoid that by seeking help/ideas here) to follow the the flow path of the water...the owner's manual diagram merely shows where the intake stops but I have no idea of the path. ANY input anyone can share in solving this problem will be greatly appreciated. This motor has served me very well for 18 years with absolutely no problems and I am anxious to get it back in good running order.

 

[washburn]

Re: Overheating Gamefisher 15HP

If it's like my ('94) the t-stat is behind a small cover at the top rear of the driveshaft housing. Last year my motor started running ragged and it turned out to be a bad head gasket. Not suggesting that's your problem.
If it's not "peeing" after you replaced the impeller then it's either a clogged passage or maybe the tube didn't seat in the impeller housing properly.
If you do have to order parts I highly recommend Mr. Marine. They are a few blocks from the factory and cheaper than anyone I've found for Mercury parts. www.mrmarineinc.com Good luck!

 

[drewmitch44]

Re: Overheating Gamefisher 15HP

washburn is right there is a black plastic plate on the back on the the top of the leg. The t-stat is in there. There is 2 flat headed screws that hold that housing on. You have to be careful when pulling it off as there is a spring in there holding the t-stat in place. I had the same problem with my 96 gamefisher. I took the t-stat out first to make sure that was the problem. I ran it without the t-stat for about a week but ended up replacing it cause the motor would not get up to temp. Also someone told me that you can mess up the heads running without the t-stat cause the block starts to get warm and the cold water hits it and warps it cause the water has no time to warm up. Good luck. BTW that t-stat was used on a lot of force motors so it should be cake to find. I think i paid 12 bucks for mine.

 

[washburn]

Re: Overheating Gamefisher 15HP

Forgot to mention, since it is basically a Mercury motor
you might try posting this on the Force or Mercury boards.
Lots more people will see it on the Mercury board for sure.

 

[oldhorse]

Re: Overheating Gamefisher 15HP

Thanks gentlemen! I'll look into those solutions. I'll try your thermostat suggestion and i do have a new head gasket in case that's part of the problem. i do have one more question though. the plate that you referred to that needs to be removed to get to the thermostat must be on the inside if the motor leg, right? mine does not have anything removable on the outside. and, if it is on the inside, what's required to get to it? thanks again!