1987 Mariner 175 overheat problem fixed

[BassRunner]

My 1987 Mariner 175 was continually overheating. I had changed impeller, thermostats, and poppet valve. Still no fix. I then removed heads and I have the 2-piece heads. My local dealer could not fix. Upon ordering head gaskets, none were the same as original. Old ones had bigger water holes and the new ones were smaller. Upon contacting Mercury Parts Division, the smaller holes are to slow down water transfer and cools head better. New gaskets installed, water tested and used with 100% fix. I even added a water pressure gauge and have my pressure too. After 1 1/2 yrs. in the process, am now waiting for this freeze to leave to get back on the water. Hopefully this helps someone else.

 

[Texasmark]

Great. I agree that you did the right thing in contacting Mercury about a design change. Really nice with something like that comes along as a result of consumer/service dept. feedback to the company. Car engines are like that also. Holes in the block are large and you have a gasket with a small hole in it.....makes you wonder unless you understand the process and know you have the right part. Makes sense.
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Mark