Inboard vibration

"Hello,
I just bought a 78 se

"Hello,
I just bought a 78 searay 30 sedan bridge with twin mercruiser 255hp staright inboards. the boat was in the water when I bought it and it was a deal i could not pass up. when i whent to move the boat to my marina i noticed the starbord engine had a slight vibration when in gear forward or reverse, engine is very smooth in nuetral. I thought it might be a bent prop and i would look at it when i took it out of the water. when i went to dock the boat using the transmisions, i had port in forward and starboard in reverse. this made the vibration very bad. at this point i was in the slip and shut every thing down. any ideas on were i should start looking.

jeff"

"Look at the prop, shaft, coup

"Look at the prop, shaft, coupler, prop nut. A little goes a long way when it comes to bent props. The nut may be loose, shaft bent, etc. Just be thorough and set everything to spec."

easy way to find out if it is

easy way to find out if it is the prop is to run 1 engine at a time and find out which side has the vibration and swap the props and see if the vibration switches with the prop. It is possible the last owner hit something and knocked the cup out of the prop that is not noticable to the naked eye.

"The props probably rotate in

"The props probably rotate in opposite directions. My guess is that one blade is tweaked and not very noticeable but as he said, he hasn't taken the boat out of the water and never looked at the drives closely before he bought it."

"could just be bad alignment.

"could just be bad alignment. recommend You check it before hauling, as it tends to change when on blocks. this will also tell if shafts are bent."

"Some noise and vibration in r

"Some noise and vibration in reverse is normal for inboards. I'm with Scott: You might simply have a bad alignment. But if you do, and the previous owner ran it that way for some time, you'll need to pull the shaft and get it checked out, along with the prop shaft bushing.

The other Jeff

PS: That's a pretty nice boat, and very rare."