Mercury 175 HP Runs Hot

[jmarcar]

I recently bought a 1994 175 HP Mercury outboard. It run fine at low and high speeds (1000rpm and above 3800rpm). It I run it anywhere in the middle the temp starts climbing. If I either slow down or speed up, the temp comes back down. I recently changed the themostats. Does anyone have any ideas what I can check next?

Thanks in advance for any help.

 

[150BlackMax]

Re: Mercury 175 HP Runs Hot

I have the same issue...I hope you can find a solution and share!!

 

[sledstew]

Re: Mercury 175 HP Runs Hot

check to see if the thermostat housing is leaking water while under pressure?

 

[jmarcar]

Re: Mercury 175 HP Runs Hot

They are not leaking.

From reading other threads on this forum, it appears having a PSI gauge might help troubleshoot the issue. Unfortunately I don't have one, but can I add one? If so, how difficult is it?

 

[gss036]

Re: Mercury 175 HP Runs Hot

There are several recent post on this subject, look at those as all are similar. Check you poppet valve. When was the water pump changed? Yes, you can install a water pressure guage, several posts on that subject as well.

 

[jmarcar]

Re: Mercury 175 HP Runs Hot

I changed the water pump and all seems well. I'm going to run it more tomorrow, but it ran very good today. Its actually running cooler than before at all speeds.

Its strange how the water pump didn't work when running at the middle rpms, but what do I know. Thanks for your help

 

[gss036]

Re: Mercury 175 HP Runs Hot

The rubber veins form the rounded position from sitting and then harden up and then really lack in performance. Sounds like the new water pump solved your problem.