1985 Mercury 150 runs hot at medium to high

[ChampionHead]

I have a 1985 Mercury 150 HP outboard. When I run it at idle (but in gear) the temp gauge reads about 1/2, but when I give it a little more gas (not enough to bring it on plane) the temp gauge moves up to 7/8 to HOT. If I put the boat up on plane, the temp gauge runs in the range of 3/4 to HOT. The water pressure is running about 15 PSI to a max of 18 PSI. As I give the engine more gas the water pressure moves up to 20 PSI briefly then backs off to 15 PSI.<br /><br />I've replaced the thermostats and there is water coming out of the pee hole. The problem was much worse before I replaced the thermostats because no water was coming out of the pee hole.<br /><br />Any ideas? Do I need to replace the poppet?

 

[Trent]

Re: 1985 Mercury 150 runs hot at medium to high

This a saltwater engine??

 

[ChampionHead]

Re: 1985 Mercury 150 runs hot at medium to high

The motor has only been used in fresh water. BTW the problem only happens under load, not out of the water with a hose and muffs.

 

[ChampionHead]

Re: 1985 Mercury 150 runs hot at medium to high

Bump

 

[ODDD1]

Re: 1985 Mercury 150 runs hot at medium to high

championhead, if you have pressure, it doesnt necessarily mean its water...maybe a recently mounted transducer throwing an air stream in the water pickups on the gearcase? maybe a head gasket on the way out? normally these motors will show under 5 psi at idle and run between half and 3/4 on the guage [at idle] over 2000 rpm they will drop temp to 1/4 and pick up +10 psi...

 

[ChampionHead]

Re: 1985 Mercury 150 runs hot at medium to high

Thanks ODDD1!<br /><br />I haven't mounted anything new on the boat in over 5 years, but I did mount a ladder on the starboard side in the rear back then. I recently noticed that it's catching water more than it used to.<br /><br />I'll remove all or part of it and see if the problem goes away.

 

[Huddleston Bass]

Re: 1985 Mercury 150 runs hot at medium to high

I have owned a '86' 150XR2 since it was brand new. One thing I noted is if the timing is off you will definately see the temp go up! <br />Just a thought..

 

[ChampionHead]

Re: 1985 Mercury 150 runs hot at medium to high

Well, it took a while, but I finally got everything running nice and cool.<br /><br />I smoothed out the rough spots in my hull right in front of the lower unit and things became a little better. Then I replaced the impeller and temperature sending unit and things became alot better.<br /><br />Thank you for all your help!!