[scottwizer]

Ok a little history on my boat... It is a 1980 spectra daycruiser with mercruiser 260 outdrive and 350 chevy. Recently done a carb rebuild and complete tune up...

After all of the carb and tune up work we went to the lake and everything was fine, no vibrations or running issues of any kind. Went to the lake last weekend and I noticed a vibration off of idle. It seemed to get worse about 1000 rpm to 1400 rpm and the vibration totally goes away. On a plane and running at hard throttle there are no issues of any kind. I just checked the prop and prop shaft to make sure they are ok, and there is no signs of the prop or shaft being bent. About three years ago I had a new gimble bearing installed and all of the bellows and seals replaced. I also checked the drive for water in the oil and it is fine. The engine checks ok with no missing and comprssion is good.
Do you guys have any ideas on where else I should look or check...? Is there a way to check the u joint or grease it? I am not much of an outdrive guy...? All of my experience is in my flat and vdrives. Thanks for the help.
Jason

 

[SoldHondaBoughtHondo]

I can't see vibrations i.e. something out of balance, getting better with more rpm or load. Will it do it on the trailer?

Are you sure it's not dropping a cylinder at low rpm and it clear itself up with more revs? Vacuum leak, plug or wire issue. Might try starting with a cold motor and run it for a short period of time, right in the zone where it's the worst, shut it off and carefully check each exhaust pipe for one cooler than the rest.