Mercury 25 hp sea pro overheating

[Snowmaker Shane]

Hi guy's,

I recently bought myself a little 12ft tinnie.
I have had it out a few times with no issues.
The last time I took her out though, we fished a while.
It was in quite shallow weedy salt water, after fishing for a bit we decided to relocate to the lake.
On route to the lake I had the throttle almost completely open but it didn't seem to be as responsive as it had been earlier in the day.
I kept cruising only to find it started to have less and less power, it didn't take long before I turned around to find steam bellowing out of it.
I immediately shut it down and the powerhead was very hot. I left it to cool and not wanting to do anymore damage pretty much start stopped in in short bursts back to the ramp. It started everytime with no issue and the pee hole had steady flow.
Since then I have compression tested it, comp is at 120psi both cylinders.
The motor should have a thermostat so I thought I'd check it.. turned out it had been taken out.
My next thoughts are replacing the water pump and impeller and putting a new thermostat in.

Was wondering if anyone else has any thoughts on my overheating issue that might point me in the right direction.
Could it be that something has just blocked it up somewhere and then either released or pushed through randomely?
The Motor is a 2 stroke 2007 Mercury sea pro 25hp.

Thanks guys!

 

[Willyclay]

Welcome to the iboats.com forum! The members here are great and can help you with any problem. I have no personal experience with that series of motor and will not suggest how you should proceed other than the obvious discovery of the missing T-stat. You might want to reverse-flush through the T-stat opening to help determine if there is a blockage. Sounds like you are on the right track. It's usually something simple. My old geezer-brain is a little concerned about your "12ft tinnie" being powered by 25HP. My first thought is that is too much and the transom may be over-stressed. Be safe!