I have a 1986 Mercury 150 XR2 (s/n 0B210616) that has a high RPM hot-running issue. The motor has only been run in fresh water, and has just had the poppet, both t-stats, and a new water pump kit replaced. A compression test revealed 110 to 115 across the board.
The motor runs with the telltale water flowing a full stream of warm water, (not hot) with no visible signs of smoke in all RPM ranges. At idle the gauge reads about 160, at 4,000 RPM it?s at around 200 degrees, but at 5,000 it jumps to about 230. When throttling back the temperature immediately drops back down.
I have verified the gauge and temp sensor are reasonably accurate and the temperatures are the same on both heads. The high-temp alarm does not sound, but I have verified the alarm does work. I have not tested the alarm sensor.
The only other things I can come up with are: 1) gasket failure resulting in exhaust gas mixing with coolant water, and 2) the ignition timing may be off.
Are there other things I should be looking at? I?d rather not pull the power head and replace the gaskets if I don?t need to.
The motor runs bit rough up to about 3,000 RPM but great above that so I suspect the timing may be off. I don?t have the correct manual so I would appreciate information on what the timing specs are and how to set it correctly.
Many thanks,
Dave
The motor runs with the telltale water flowing a full stream of warm water, (not hot) with no visible signs of smoke in all RPM ranges. At idle the gauge reads about 160, at 4,000 RPM it?s at around 200 degrees, but at 5,000 it jumps to about 230. When throttling back the temperature immediately drops back down.
I have verified the gauge and temp sensor are reasonably accurate and the temperatures are the same on both heads. The high-temp alarm does not sound, but I have verified the alarm does work. I have not tested the alarm sensor.
The only other things I can come up with are: 1) gasket failure resulting in exhaust gas mixing with coolant water, and 2) the ignition timing may be off.
Are there other things I should be looking at? I?d rather not pull the power head and replace the gaskets if I don?t need to.
The motor runs bit rough up to about 3,000 RPM but great above that so I suspect the timing may be off. I don?t have the correct manual so I would appreciate information on what the timing specs are and how to set it correctly.
Many thanks,
Dave
