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I have a 1991 90hp and get an overheat alarm when the motor has been run at high speed, stopped for a short period of time (approximately 10 minutes)and restarted. It takes a while (seems longer than normal)for any water to come out of the pisser and it seems steam comes out at first. I usually run at slow speed for a while and the alarm will eventually shut off and the motor seems to operate fine. Thought it was the impeller and\or thermostat and changed those but the problem is still happening. Any ideas what might be causing this?
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Shrbnd,
Assuming that your water pump and thermostat are doing their job - I would check the pressure control valve (aka PCV, pressure relief valve, poppit valve). It is designed to open at pressures greater than 20 psi to relieve over-pressure in the water jacket. This valve can get stuck open with debris/mineral deposits and dump cooling water out the relief holes at the top of the upper casing. When this happens, there will not be enough cooling water to keep the motor from overheating.
If the PRV checks out ok, then the only thing that is left would be the water jacket of the head - may be clogged with salt/sand/mineral deposits. You have to remove the head to clean out the water jacket.
Your water pump may also be starving for intake water at high speed. Do you notice a drop off in water pressure at the higher speeds? Does the pee-stream drop off at high speed? Have you added a jackplate recently and maybe running the motor too high out of the water?
Also, when you get an overheat alarm, just throttle back to neutral and let the motor run at idle - look to see that there is still a pee-stream. The motor will cool down faster than just shutting the motor off and letting it sit there.
Ken K [img]smile.gif[/img]Comment
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