2001 Merc 150 Saltwater Series Overheating

[JamNJ1955]

My 150 HP recently started overheating around the 2000 - 3000 RPM range, I am thinking impeller or thermostats. Any other ideas? How hard is it to change these items?

Thanks

John

 

[gss036]

Re: 2001 Merc 150 Saltwater Series Overheating

Does not sound like you have overheating at idle/slow speeds. I would be looking at the poppet valve. Either has crud trapped in the cavity or stuck closed. It should open around those RPMs and release excess water from the block. It is located on the lower starboard side of the block and the cover looks like a figure 8. It is easier to access if you remove the lower cowling on that side.
Could be time for a new water pump and thermostats anyway if they are all orginal.

 

[j_martin]

Re: 2001 Merc 150 Saltwater Series Overheating

A water pressure gauge is very handy on that engine. Normally it'll run a few pounds at idle, run up to about 12 lbs between 2000 and 3000 rpm, then drop back a little and ramp up to about 20 or 25 at WOT. If you get used to how it runs, you have early warning when something is plugging up or sticking.

For instance, in your case, if the pressure was running too high, go straight to the poppit valve. Too low, look to the impellor. Too low at Idle, either impellor or t-stats.

T-stats and poppit are gravy work. You need gaskets to go into the poppit, T-stat gaskets are rubber, and if they are properly installed can be reused. Either one is lunch break type hand wrench work.

hope it helps
John

 

[JamNJ1955]

Re: 2001 Merc 150 Saltwater Series Overheating

Thanks Guys