So, as per the subject, I have a 2002 Mercury 150 EFI with a specific overheating problem.
When I start it and leave it idling, it has a good water tell tale and no overheating problem.
At 1400 RPM the temp gauge increases to over half (merc analogue gauge), the over temp continuous alarm sounds and the engine speed appears to then be limited to about 3200 RPM.
This took 20 minutes at 1400 Rpm, but I was deliberately running at this speed to find any problems.
When I stop and run the engine out of gear for 5 minutes it cools down and the alarm stops.
Then, with the alarm off and the gauge below half I can get up planning and I don't have an overheat problem.
I spent 1.5 hrs on the water today finding out exactly how it is being used when it overheats.
In the last two weeks I have had a new pump impellor installed, changed the; spark plugs, thermostats and removed and cleaned the poppet assembly. There were 3 small stones and a tiny piece of stick in the poppet table cavity after the valve seat.
I have read possibly 25 or 30 discussion threads on similar problems that others have had with similar motors and all suggestions include what has been done.
I want to take it 40km off shore but not until I'm happy I won't have problems.
It has been used exclusively in salt water, almost always washed after use and has done 260 hrs.
Somewhat frustrating motor!
When I start it and leave it idling, it has a good water tell tale and no overheating problem.
At 1400 RPM the temp gauge increases to over half (merc analogue gauge), the over temp continuous alarm sounds and the engine speed appears to then be limited to about 3200 RPM.
This took 20 minutes at 1400 Rpm, but I was deliberately running at this speed to find any problems.
When I stop and run the engine out of gear for 5 minutes it cools down and the alarm stops.
Then, with the alarm off and the gauge below half I can get up planning and I don't have an overheat problem.
I spent 1.5 hrs on the water today finding out exactly how it is being used when it overheats.
In the last two weeks I have had a new pump impellor installed, changed the; spark plugs, thermostats and removed and cleaned the poppet assembly. There were 3 small stones and a tiny piece of stick in the poppet table cavity after the valve seat.
I have read possibly 25 or 30 discussion threads on similar problems that others have had with similar motors and all suggestions include what has been done.
I want to take it 40km off shore but not until I'm happy I won't have problems.
It has been used exclusively in salt water, almost always washed after use and has done 260 hrs.
Somewhat frustrating motor!
