2004 4.3L Mercruiser with an Alpha One Gen 2 drive in a Caravelle 187. Direct raw water uptake.
Couple seasons in and the issue seems to be occurring faster each season. While throttled up the engine cools quickly. While at idle it will quickly alarm.
First thing I did was to replace the raw water impeller. No obvious problems. After that I assumed it was the thermostat. Replaced it and checked the thermostat in boiling water and it was operational so that was not the issue.
Last season I had replaced the bellows so I assumed the water hose was pinched. Just redid the entire bellows job. The exact same overheating issue is evident.
I pulled the raw water line from the thermostat housing and cranked the engine and there was no water flowing from the raw water side. Is that an accurate test?
There is a power steering cooler between the outdrive and the thermostat housing. My current thinking is that the small passages of the power steering cooler are clogged. I'm reading that I should back flush. I have not found any good instructions. Do I just clamp the hose connected to the thermostat onto a garden hose?
Do I need to remove the outdrive before I backflush? I hesitate to backflush into the impeller because I assume that when I restart the exact same material will get clogged again.
Any thoughts would be appreciated.
Justin
Couple seasons in and the issue seems to be occurring faster each season. While throttled up the engine cools quickly. While at idle it will quickly alarm.
First thing I did was to replace the raw water impeller. No obvious problems. After that I assumed it was the thermostat. Replaced it and checked the thermostat in boiling water and it was operational so that was not the issue.
Last season I had replaced the bellows so I assumed the water hose was pinched. Just redid the entire bellows job. The exact same overheating issue is evident.
I pulled the raw water line from the thermostat housing and cranked the engine and there was no water flowing from the raw water side. Is that an accurate test?
There is a power steering cooler between the outdrive and the thermostat housing. My current thinking is that the small passages of the power steering cooler are clogged. I'm reading that I should back flush. I have not found any good instructions. Do I just clamp the hose connected to the thermostat onto a garden hose?
Do I need to remove the outdrive before I backflush? I hesitate to backflush into the impeller because I assume that when I restart the exact same material will get clogged again.
Any thoughts would be appreciated.
Justin
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