Force 120hp Major Overheat

[HenHouse]

Hello all, 3 weeks ago I bought my first boat with a Force 120hp outboard. I got a smoking deal and purchased it knowing it was overheating. I've done the following to solve it to no avail, and made a dumb mistake. This forum has been invaluable so far, and I appreciate all the help I can get.

Tested on water before anything else with an infrared laser, and the alarm is working properly.
Replaced impeller and housing. Ensured it was installed correctly.
Replaced the thermostat and tested it on the stove. It works correctly.
It still overheated

I thought it could be a blockage. So I did the following
Replaced exhaust cover gaskets and cleared some minor blockages.
Replaced the head gasket and cover. No blockages.

I took it out this morning to test it after replacing the gaskets. I made a dumb mistake and had my infrared laser set to Celsius. I'm not sure how I did not think to check this. The alarm went off, but when using the laser, I thought I was within the proper operating temperature. Tested on the trailer and out on the lake. The engine was on for about 20 minutes, and about 6 minutes were on plane, the rest were at idle. I continuously read the temps throughout this process in Celsius thinking I was okay. I caught my mistake once back on the trailer. The hottest temp readings I got are as follows.

On trailer testing - 132C / 270F
Tested on trailer in reverse - 180C / 356F
Idled from trailer to dock - 113C / 235F
After 1 min plane - 115C / 240F
After 1 min 30 seconds plane - 125C / 257F
After 5 min plane and 1 min idle back at trailer (when I noticed) - 214F
The engine ran well the whole time only thing I noticed was excess smoke.
No clunking or seizing

Since this I've dropped the lower unit, and the impeller is still good. Removed spark plugs, and they seem ok. I'm not sure how to proceed. 365F is insanely hot, and I can't imagine I didn't cause major damage. Should I do a compression test? Take the head back off and inspect?
I think the overheating issue is due to a possible gasket/o-ring failure at the top of the water tube and exhaust jacket. Do I even try and fix the overheating after getting it to these temps?
Another thing to note is it doesn't overheat on muffs but on the lake, it does.

Please help.

 

[jerryjerry05]

More info? year?? Pic of the pump, housing?
IF??? the boat had set for a long time? the insects get up in the holes and make nests for their new young. Usually this gets blown out when the waters put to the motor, but in severe cases it won't.
Snake camera: drop the lower unit and see if the water tube is in the right place?
While the lower unit is off: hook a water hose to the water pipe and run it and see if it still gets hot, if so then there's a blockage in the bottom odf the block, Good luck.

 

[HenHouse]

Not sure on the exact year and model because the ID placard on the transom bracket is missing. From my own research, I think it's a 1993 or 92. It has power trim not sure if that changes anything. I'll attach pics

Before changing the gaskets, I ran it with a hose hooked up to the water pipe, and it didn't overheat. Water does escape from what I think is the top of the water pipe as soon as I push water up the pipe. There is a small gap where I can see the tube through the exhaust side. When water is pushed up, I can see it splashing around and coming down. I think the reason it doesn't overheat on muffs/the hose is because it provides more pressure and overcomes the leak. Additionally, I suspect that I may have an exhaust leak that is entering the cooling system.

I did a compression test this morning and got these numbers. Not sure about the reliability of my tester, as it is a cheap one from Harbor Freight.
1 - 138psi
2 - 139psi
3 - 135psi
4 - 132psi
I think that is a good test and indicates I didn't cause major damage with the overheat.

As far as I know, the boat didn't sit for a long time, but I can't confirm that. There is a possibility it sat for a season or two because there were leaves in the hull.
I'll also try and get a snake camera as I don't have one.
Thanks

 

[Jeff J]

I would check the timing too. Not familiar enough with 2-stroke to know how much difference it can make but ignition timing can affect engine temperature.

 

[HenHouse]

Attached is a video to demonstrate the leakage found at the top of the water tube when I attach a hose. Not sure if this is normal or not. Hope this helps with what I'm trying to describe.