temp. for 1992 Mariner 150 Magnum II

[avian22]

Haven't had a problem. Just seems really Hot.

Under 3000. . . No problem! When I "Put it Down" temp. goes up to like 190-200 and stays there (doesn't over heat). Just wondering. . . Is that normal? Used it several times and hasn't created any problems.

Been told that "the higher the rpm's, the lower the temp. because there's more water pumping through". And I've also been told that "the higher the rpm's, the higher the temp. because the pistons are working more" (this makes more sense, but I'm not a mechanic. . . YET!)


Thanks

[BigLew]

Try an extended flushing with a salt removing solution. (Out of water and running in a tank for a while.) It could be that you have enough salt/crud build-up to restrict max flow. Just an idea and a cheap "fix."

You might also add a second run using a mix of H2O and white vinegar. The mild acid will tend to dislodge/ disolve mineral deposits as a result of higher alkaline water sitting in the warter jackets between uses. I shouldn't harm any of the surfaces.

[stumpie2]

sounds to me like you have a poppet valve that isnt completly opening or not opening at proper temp. also if the motor has run hot in the past the wax inside the copper or brass 'cup" on the thermostat wont force the thermostat to open at the proper temp. as the wax gets hot it expands and pushes the tstat open if it has been extremely hot before and some of the wax expands out this would cause the tstat to not completly open or open at a higher temp. just my 2 cents

[Blue_Heron]

I have a 1991 Merc 150 XR4. Your Magnum II is the gray version of the same motor. My engine temp stays constant around 160 after initial warm up regardless of load.

My XR4 experienced the same problem you describe after the powerhead was rebuilt a couple years ago. Turned out the poppet valve was reinstalled incorrectly. If you have a water pressure gauge, it should read between 10-15 PSI at cruise. If the pressure is way up at cruise, and your temp gauge swings back and forth between 180 at cruise and 120 at idle, I would say it's probably the poppet.
Dave

[avian22]

Thank you gentlemen. Gonna make immediate inquiries on both ideas.

So most Defenitely not ok to be running at 190 something degrees at 3500rpm's right?

[Bushwacker]

Salt starts to come out of solution at about 160, which is why most marine engines are set up to run cooler than that. If you run hotter than 160F on any raw water cooled engine, you're building up salt deposits!

[eggsuckindog]

I think 140 is a good target - I would also look at the poppit valve

[Blue197320]

i think my 84 runs a little cooler than that while on plane. then again i dont have t-stats either. altho last time i was out i had perfect water pressure but temp went a little higher than normal. poppet is pretty new too and so is water pump.

[stumpie2]

no t-stats is the worst thing you can do to an engine. although the gauge says cool or normal the engine is saying different. with no t-stats the water has no restriction therefore it is not staying in the engine long enough to "soak" up the heat and remove it from the engine. the water passing the temp sensor is cool because it hasnt been in the block long enough to warm up there for the gauge is showing a inaccurate reading. this will almost always result in a very short engine life or a very expensive repair bill

[Blue197320]

at the yearly maintence time ill put stats in it and take out the restrictors and check it out.