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1989 Merc 200 HP/ do I have a cooling problem

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  • 1989 Merc 200 HP/ do I have a cooling problem

    Looking for advise on cooling system on 1989 Mercury 200hp.
    I had my boat out today and ran about 30 miles, running great. Water temp was 48 degrees.
    I took it out to a lake to run the motors (kicker/main) to get a good flush, if the weather turns nastier, the season could be over
    for a few months. When I ran the 200 in the cold lake water, I got very little water in the tale, tale and then nothing. The lake water was probable 40 degrees. Pulled the cowling and felt the heads, both were warm, I could hold my hand
    on them for several minutes if I wanted to, maybe 120/125 degrees.
    When I got home, (motor not running) I pulled the tale-tale hose inside the cowling and ran water with about 35-40 lbs pressure, got a flow
    through prop and the 2 small holes by the cavitation plate. Next I
    fired up the engine on muffs and hose, after about 45-60 seconds, I got a good water flow from the tale-tale. Do I have a problem with thermostats or poppet valve? The impeller only has about 25 hours run time on it and was changed in the spring of this year.
    I have never changed the thermostats, so I think that will be my first thing to do. I have never had a poppet valve apart, can’t be too
    difficult(?) Can it?
    Any ideas or suggestions would be appreciated.

  • #2
    This is pretty typical when the water is that cold. The reason you had a good flow on the hose was you had quite a bit less flow and the motor equalized the temp so the thermostats where able to open.

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