Hello,
I ran a can of Seafoam Spray Top Engine cleaner and lube through my A4. It did increase the max RPM from 2000 to 2100 on open smooth water and the engine seems a little smoother at 1600 cruising. During my recent two week cruise, with lots of motoring, the engine started a tapping sound at 1600+ RPM. I suspect it's a valve. I have had the boat for 17 years and it's never made this tapping noise before.
I have read many of the entries on valve tapping here and the reason I am posting is because some people stated they hear the tapping at low RPM and not high. Mine is opposite, I hear it at high RPM. If I cover the flame arrestor on the carburetor it does suppress the tapping noise. I suspect the noise is still there and I am hearing it through the carburetor when not covered. Wondering if anyone else has an engine doing what mine is?
The valve clearances have not been check, probably since the engine was new in 1975, 1300 hours. Compression numbers were 95, 95, 75, 105 before the Seafoam. I am going to do the Seafoam again and then check compression. The 75 bothers me and the max RPM of 2100 is lower than I would like. Indigo prop. I am probably expecting too much with the engine cleaner but it did help and it's cheap and easy.
1975 C&C 30.
Chesapeake Bay
I ran a can of Seafoam Spray Top Engine cleaner and lube through my A4. It did increase the max RPM from 2000 to 2100 on open smooth water and the engine seems a little smoother at 1600 cruising. During my recent two week cruise, with lots of motoring, the engine started a tapping sound at 1600+ RPM. I suspect it's a valve. I have had the boat for 17 years and it's never made this tapping noise before.
I have read many of the entries on valve tapping here and the reason I am posting is because some people stated they hear the tapping at low RPM and not high. Mine is opposite, I hear it at high RPM. If I cover the flame arrestor on the carburetor it does suppress the tapping noise. I suspect the noise is still there and I am hearing it through the carburetor when not covered. Wondering if anyone else has an engine doing what mine is?
The valve clearances have not been check, probably since the engine was new in 1975, 1300 hours. Compression numbers were 95, 95, 75, 105 before the Seafoam. I am going to do the Seafoam again and then check compression. The 75 bothers me and the max RPM of 2100 is lower than I would like. Indigo prop. I am probably expecting too much with the engine cleaner but it did help and it's cheap and easy.
1975 C&C 30.
Chesapeake Bay
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