Yanmar 3hm 27 hp questions Vibration and engine mounts

" Hi there,
I have a 3hm engi

" Hi there,
I have a 3hm engine in a 31 ft steel yacht.
At approx 1000 rpm it develops quite a bad "harmonic" vibration. It runs very well, starts easily etc, and idles smoothly. At approx 1400 rpm the vibration completely clears up, and the engine runs smooth again. The engine mounts seem very soft, (although all appear to be in good condition),I was wondering if this could let the engine move more than it is supposed to?
Your advice would be great! "

" Richard, could be a number o

" Richard, could be a number of things.If this is the only speed that you get a vibe, it could be just harmonics, and not much to do about it. First and foremost your shaft and drive/engine have to be in alignment. This is a job for the pros, trust me on this one! Secondly your prop should be checked for balance, bend blades, nicks, etc to be sure this is not an issue. Usually if props are messed up they will vibe at most RPMs. The mounts you speak of may be an issue at certain Revs, as I just repowered and my diesel has rubber mounts. What you loose in noise dampening, you sometimes gain in vibration, particulary at certain RPMs. Its not a perfect world, Good luck, Kim "

"Have the same problem at 1100

"Have the same problem at 1100 only, a bit more throttle or a bit less and it runs smooth as silk (well almost)..This happens on neutral or in gear so It is not he drive system....must be normal ??????"