Hi

 We have a Beta 38 hp marine engine in our 36 sailboat.

 The first two years we did not remove the stack tube and clean it. We did not realize the Beta manual said every year.

 We have since replaced the stack tube O-rings every year and replaced the antifreeze.

So we have had our Beta 38 hp engine for 6 1\2 to 7 years.

I just tried to replace the O-rings on the Beta 38 stack tube and it will not stop leaking. The (using fresh water to test for leaks) water keeps coming out the flange that goes to the impeller. After a half dozen tries and we called a mechanic.

He sent out the stack tube for testing and it tested fine.

He installed the stack tube and it leaked. Then tried again with larger O rings and it still leaks at the same place.

 He says that the stack tube will never seal and the heat exchanger needs repair or replacing.

This week he is removing the heat exchanger and will have it welded and machined so the O-rings will seal.

 He said that on average the heat exchanger lasts about 7 years.

So my question is this, even though I do O-ring replacement and cleaning every year I thought we would never need to repair
eplace the heat exchanger. Silly me. But how long do they (heat exchangers last) usually on the Beta, on a sail boat? We are cruising the Mexican Riviera pacific coast of Mexico - for the last 6 years.

Also we use a Stant radiator cap pressure tester to test for leaks. How many ponds of pressure to use. I tried 12, the mechanic says only 3-4 pounds is necessary?

 Thanks,

Chip