Shaft Vibration (M18) .......

[Bob]

I am hopeing someone had the same problem and can provide some assistance. I have a Universal M18 (490 hours) on my '88 Catalina. A few weeks ago I adjusted my packing gland nut a few turns to minimize the water drip. Additionally I note that an engine motor mount nut (that which holds the engine to the mount) was missing. I replaced the nut and tightened down.Under power this past weekend I noticed a very strong vibration at 1400 rpm on up. I put the tranny in neutral and revved to 1800+ and noted it was nothing in the engine. It felt like like a strong cavatation and must be the shaft.My quesiton is, can tightening the packing nut or replacing a missing engine mount nut cause a shaft misalignment? Could this be characteristic of a cutlass bearing going bad? I have yet to dive down to see any debris is wrapped around the shaft, prop, zinc or shaft.Any input is always appreciated.ThanksBob'30 Catalina

 

[h2opuppy]

Time for re-alignment

As unpleasant as it sounds, re-alignment is now on your work list. The vibration and resultant damage will only get worse.We are new to boat ownership and took time to figure out that poor alignment on our boat was causing horrificly loud rotating noise. I finally listened to some experienced mariners and began re-alignment, replaced cutless bearing, and re-alignment once back in the water.When I unbolted the driveshaft coupling, the source of the noise was obvious. The gap was way over .030", when the proper alignment tolerance is .003". Once back in alignment, the noise was quieter, and sounded further aft. We sent the boat to the yard for cutless bearing replacement. One day and several boat bucks later, she sounded much better. But on the advise of the yard, I re-aligned again. So far, no vibration or noises.Since I had never done this task before, it took me 3 weekends to figure it out. It is a tedious task, spending time as a pretzel, then moving the engine minute amounts, then measuring. Now that I know how to do this task, I will check the mounting bolts and alingment periodically.

 

[Bob]

Thanks

I ran the same post on "ask another sailor" and got pretty much the same response. Everything was fine until I decided to replace that engine mount bolt and torque everything down. I thought that the rubber in the mount would make up for an change in alignment under power. What I thought was a needed repair, turned into a slow ride to port yesterday! I never realized the sensitivity in the alignment changes. I can only hope I did not damage the cutlass. The 30 Catalina manual has an alignment section that I will follow. Appreciate the feedback.Bob