vibration issue - new mounts last year

It seems like my right of passage every spring to be contemplating or doing an alignment. It is literally the only thing I get help with so of course I need to chase the guy.

Last winter, I replaced all the mounts on both engines. The guy helped me with both sides and they were .003 or better. As soon as I splashed, I felt a vibration at low speeds on the Stb side, port was perfect. It was better at cruise and I just lived with it all season. I immediately thought alignment but a misfire crossed my mind. I even checked each plug wire with my timing light at the dock to make sure they were all firing which they were. I'll dig into this theory more...

I checked the prop for a bent blade and it's perfect. I didn't hit anything and because I used Prop speed, I would have seen something if I did. I can rule out dirty bottom or anything on the running gear because it was noticeable on my first run. Shaft was replaced a few years ago and was perfect the prior season. I checked the alignment and it's dead on. There' no binding, shaft turns easily by hand, cutless bearing is new and shaft is relatively centered on both ends of the strut.

My only complaint is I would like the shaft to be more centered in the shaft log, it's more towards the left hand corner. Shaft is not touching, I did check that.

What do you guys think? Can I rule out an alignment issue because I feel it at low speeds?

Bob

I'd say rule out alignment due to your measurements...

how "bad" is the vibration? many boats have one rpm where minor vibrations exist...just avoid that rpm...bad or major vibrations are a completely different matter...

I would realign it, or at least check it.

Did you let the boat sit in the water for a week before the alignment?

Jeff

Just to clarify the timeline. Pulled boat fall of 2013 and both sides vibration free the whole season. Changed the mounts over the winter of 2014 and immediately felt a vibration on the Stb side upon launch. Boat sat in the slip for 3-4 days before we re aligned. The port said didn't require any adjustment, Stb was very minor.

In checking the Stb side now (still on the hard), it's dead on. I distinctly remember feeling it the first time at a very low speed as I was powering up. Mark, to your question it wasn't bad enough that I didn't run it all year but also bothered me all year too. If at a dead stop powering up one side compared to the other is like night and day.

I'm trying to figure out if there are any underwater issues that I should deal with now before I splash. I keep coming back to the mounts/alignment since that's the last thing I touched but maybe that's a coincidence. Would a misfire give a similar feeling? I've read that the 454's will run on 7 cylinders and it's hard to tell. I'm going to get it running again this weekend and check everything related.

The only other tidbit of info. Due to the boat design, my engines are mounted at a pretty steep angle. Plus the angle of being blocked, both engines "slid" back about 1/8" back when I had all four mounts loose. I didn't realize it until after the fact. I can see the shiny section(s) on the shaft that were previously inside the cutless bearings. Both sides
are the same in this regard. I can't imagine this could be the issue especially since my issue is distinctly on one side.

What do you guys think?

Bob