rattle at 2800rpm

[fluidjuice]

I have just bought a second hand 25hp 2006 mercury two stroke that has only been used for an hour before i had it, so i am now breaking it in (about 2hours into it, no more than 3000rpm on double oil.
only Today i have noticed that the engine starts to vibrate /rattle as i hit 2800 rpm's then stops again at about 2900/3000rpm's, is this normal
as i havent noticed it before.

 

[sschefer]

Re: rattle at 2800rpm

I haven't really got a clue so the first thing I would check is the prop. Is it straight? Even a good looking prop MIGHT produce a harmonic effect and cavitate above normal at a specific RPM if it is out of balance. I guess you would really have to swap props to test that for sure.