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Need a little help

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mcgillr73

New member
I have a 1986 200hp Black Max at low RPM it runs hot I have put in new water pumps new t stats i have washed out the block with a hose thru the top and bottom but still have the same problem can you help
 
What do you consider "low rpms".

The flow of cooling water is controlled by the thermostats at idle/just off idle (not carved in stone but up to about 1500 rpms).

As your rpms (and water pressure) increase above 1500 the poppet valve starts to open allowing more water to cool the (heads) upper water channels.

At full throttle, the poppet is fully opened and not much is slowing the water from passing through the channels.

The poppet is (spring loaded). The one set of specs that I refer to show that you need 4 psi (up the water tube into the channels) to "start opening" poppet - it takes 9 psi to open it completely - so in the "in between psi's", it should gradually open to allow more water to pass as your rpms increase (beyond 1500'ish).

So, if you have never serviced the poppet, and you consider "low RPM" to be somewhat above 1500, then that could be your culprit.
 
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