Prop shaft alignment: on the hard or in water?

[ferrailleur]

I read somewhere that it's better done in water.
A boat mechanic told me today that it doesn't matter for a sailboat.... It makes a difference with a power boat.
Any truth here?
He said that when I mentioned that I needed a prop shaft alignment (per my surveyor) and he saw my boat on the hard. Maybe he was expecting a job right away?
He quoted me $800 (6 hours) for alignment, new cutlass bearing and repacking the stuffing box (parts included).
Reasonable?
Thanks

[sailormed]

I think it is better done in the water. Anyway, it is your boat, your money, your decision. Take your decision accordingly.

[doublebubble]

As I a marine engineer I can advise you it is best done in the water, power or sail it does'nt matter, done on the hard can be performed but must be re-checked once splashed, run up and recheck.

Regards Rod

[Sailmon]

Definitely better in water where boat/engine operate. Should actually be floating for 24 hours or longer before aligning, so Boat can take it’s floating shape based on keel hanging rather than boat sitting on it and impact of rigging load. Number of hours seems a bit high - but not outrageous. I sometimes negotiate a time & materials not-to-exceed agreement for a well defined job. Some less well defined jobs are at higher risk for unforeseen conditions and harder to set cap. Reason for NTE agreement is boatyards sometimes worry about unforeseen conditions and cushion their quotes.

[iyamwhatiyam]

Originally Posted by ferrailleur

I read somewhere that it's better done in water.
He quoted me $800 (6 hours) for alignment, new cutlass bearing and repacking the stuffing box (parts included).
Reasonable?
Thanks

All you have to do is re-read your own post for the answer to that question!!! Mr. Mechanic definitely would be happy to help you out.

In reading through my factory doc for the Universal M25XP on a 1989 Catalina 30 MKII, just last night in fact, it advises to perform the alignment in the water. Surely a boat will bend very slightly being supported by stands, and it doesn't take much.

[Sailmonkey]

Always in the water. All boats change shape when on the hard.

[capt jgw]

In the case of a new engine installation you can get it close enough on the hard to safely make it out of the launch well, then fine tune it a day or two later. If you're just checking or trouble shooting noise or vibration, you have to do that in the water. It does make a difference, and on more lightly built boats maybe a lot of difference.

[Wotname]

Yes, complete agreement on the above posts.

Final alignment must always be in the water but on a new (or reworked installation), first on the hard is OK and then in the water.

[Suijin]

As for the time estimate given it seems lengthy but not absurdly so. Some cutless bearings can be a real @&$! to get out. And if the alignment is seriously off it can take time to correct.

I would not take the surveyors word as gospel. There may be other issues in play. For example a bent shaft can look like an engine alighnment issue to someone performing a cursory check.

[ferrailleur]

Originally Posted by Suijin

As for the time estimate given it seems lengthy but not absurdly so. Some cutless bearings can be a real @&$! to get out. And if the alignment is seriously off it can take time to correct.

I would not take the surveyors word as gospel. There may be other issues in play. For example a bent shaft can look like an engine alighnment issue to someone performing a cursory check.

Thanks,
But wouldn't a bent shaft creates noise and vibrations? None of that here!

[hamburking]

Best done in the water.

On the hard, the keel is pushing UP into the boat. In the water the entire weight of the keel is hanging DOWN.

The hull is long and thin (thickness relative to the boats length). So the hull is going to bend...this is normal. Tension from the forestay and backstay pull the ends of the hull UP, and the keel pulls the middle DOWN.

So to get a good alignment, the boat should be in the water with the mast up and the rig tuned.

[jasbee]

MUST be done in the water. It depends to a degree on the hull material but it should always be re-checked once in the water. We had a wooden carvel built yacht and thought that the engineer/cowboy had done the job properly (in Krabi, Thailand), but he did not do this and we had endless vibration issues until we finally figured out the problem.
You also need to be there to make sure things are done properly. This knowledge from hard-won experience.

[mjgill1]

I think it's best done in the water. Splash the boat, let her hips settle out for a week and then get after it. I've done mine twice. Once after a new Cutlass bearing, and then after replacing my PNY dripless seal. Took about an hour each time. Edit to answer the price question. $800 seems reasonable for everything that he's doing. Sometimes those Cutlass pairings can really be a bearcat!

[Cheechako]

It MAY not matter. You wont know how well it stays as set unless it's checked in the water. That's not a bad price for what he quoted.

[kmcshane]

After installing a replacement Yanmar 3GM30F, and not knowing squat about shaft alignment, I turned alignment over to Oasis Marine, St Augustine (highly recommend).
They tried to align in the water, then hauled out, removed the rudder to gain access to the shaft.
The result was an expensive ($2500) and expertly aligned shaft, sealed by an expensive PPS shaft seal retailing about $360, with usable life of up to 40,000 hours (https://www.shaftseal.com). The seal is dripless and, so far, maintenance free.
I was working out of town at the time of their repair, but the faint clunking sound after my engine change was going to be a problem.
My attempt left a tail shaft/ prop shaft misalignment of about a thin slot screwdriver. Oasis measured their alignment as 0.003" shaft to shaft.
PPS allows for even this small discrepancy.
It's been five years with only dust under the seal.