I have a 87 Newport mkIII with a Universal m-18.
The boat does not have a thermostat and runs about 150 degrees.
I see where the universal part is for 160 degrees but the specs for the
M- 18 says to run at 165 to 195. A mechanic told me that I should use
a hotter thermostat as I have a fresh water systems not raw seawater
running though the block and if I run at 160 I will get carboned build up.
Can anyone explain why I would need the 160 degrees? Do anyone you offer one that
is hotter i.e. 170 degrees.

One more issue I have is that according to the specs this engine
should go up to 3200 RPM under load. It will go that far or more when
out of gear but will only go to about 2200 RPMs when in gear. It
reaches this and I still have about a ¼ of the throttle left, but no
more RPMs. I have replaced all the fuel filters. Now have a 30 micron
on primary racor and .02 micron on the secondary by the engine. I have
had the prop balanced and checked. It is a 13” x 12 pitch. Which I was
told by the prop guy is correct for this boat. Other than this the
engine runs fine. I was told that the problem may be the fuel pump. it
may not be providing enough pressure. What is the proper pressure for
the recommended fuel pump. any ideas?

Hi,
Your techs on the right path the hotter the engine runs [within limits] the cleaner the burn it will also run quieter, smoother while producing more power@ 180f [82c] . Most engine fuel feed pumps run @ 4--12 psi. Your rpm problem sure sounds like a prop issue,check around your area for the same installation or boats ''for sale'' specifications .