Hot Mercury 150's

[grandx]

Have (2) merc 96 150hp saltwater series, with 14.5 x 19" props. Engines cool fine at idle, engines cool fine at cruising speed (150-160). (both) engines run warm 190 - 200 F when trolling with single or double 2000-2500 rpm... With a light load can achieve 55-5600 rpms, with a full load I am over 5200 at WOT. What is the culprit here? or is this acceptable (alarm does not sound till 240 and goes off at 210 according to manual.

 

[grandx]

Re: Hot Mercury 150's

To the top.<br />Did not want to lead anyone, but I have new thermostats, new impellers, old ones were fine when I removed them. I'm thinking poppet valve... Do you think the spring is too weak or too strong, hole in diaphram???

 

[greg baranitsky]

Re: Hot Mercury 150's

I'am also having similar problems with my 98 mariner 150. Does anyone have any suggestions on this problem??

 

[Dave Clark]

Re: Hot Mercury 150's

Poppet valve is a likely culprit. The more spring tension, the less water flow. But before you go smooshing the spring down, check the fit of the plastic piece into the rubber grommet in the block, make sure it can slide in and out easily. If it is binding it will restrict water flow.