Engine to Prop Shaft Alignment with boat out of water vs floating?

[Mazu]

Mine wouldn't line up at all on the hard. About 3/16 off. Boat was on the hard for 2 years. Anyone says a boat doesn't flex...well. my owners manual recommends checking alignment after rough seas as this could cause enough flex to result in misalignment. Many think alignment is a set and forget but it has to be rechecked several times per year and after certain conditions like very rough seas. I had flex. My boat is a 1973 Morgan with a hull thickness over 3/4 inch in places. Make sure the shaft is watertight, put it in the water then connect the couplet and do the alignment. Check it again after operating the boat for a week or so.

[Cadence]

Originally Posted by Mazu

Mine wouldn't line up at all on the hard. About 3/16 off. Boat was on the hard for 2 years. Anyone says a boat doesn't flex...well. my owners manual recommends checking alignment after rough seas as this could cause enough flex to result in misalignment. Many think alignment is a set and forget but it has to be rechecked several times per year and after certain conditions like very rough seas. I had flex. My boat is a 1973 Morgan with a hull thickness over 3/4 inch in places. Make sure the shaft is watertight, put it in the water then connect the couplet and do the alignment. Check it again after operating the boat for a week or so.

I am really surprised a Morgan flexes that much, interesting.

[Mazu]

I am really surprised a Morgan flexes that much, interesting.

So was I. I think it was how the yard blocked it that caused the misalignment. Only keel blocks fore and aft and nothing in the center. I was organizing the boat paperwork recently which contains the original manual as well as a set of service bulletins. This is where I found the alignment information and the recommendation to recheck alignment after sailing in rough seas. Who would have thought.

[Cadence]

Originally Posted by Mazu

So was I. I think it was how the yard blocked it that caused the misalignment. Only keel blocks fore and aft and nothing in the center. I was organizing the boat paperwork recently which contains the original manual as well as a set of service bulletins. This is where I found the alignment information and the recommendation to recheck alignment after sailing in rough seas. Who would have thought.

Again that is interesting, I thought Morgans of the era were built like the proverbial "brick sh$t house". I wonder if the manual isn't over kill or if it maybe engine mount related more so than hull flex after rough seas?

Just thoughts from an idle mind. Thanks for the additional info..

[james247]

Originally Posted by Cadence

Again that is interesting, I thought Morgans of the era were built like the proverbial "brick sh$t house". I wonder if the manual isn't over kill or if it maybe engine mount related more so than hull flex after rough seas?

Just thoughts from an idle mind. Thanks for the additional info..

A boat is like a woven basket. Regardless of the material it is made of..
The terms supported and suspended are the technical terms.
You can't do an alignment of shaft off the flywheel through a Skeg in the water. But you can't finalise it out of the water unless it's your intent to leave it there.
Yachts twist in a sea with full sail. They are amazing pieces of engineering. Nothing's square level or any other form of geometric norm. But in the main very beautiful. Not dissimilar to my wife

[Cadence]

Originally Posted by james247

A boat is like a woven basket. Regardless of the material it is made of..
The terms supported and suspended are the technical terms.
You can't do an alignment of shaft off the flywheel through a Skeg in the water. But you can't finalise it out of the water unless it's your intent to leave it there.
Yachts twist in a sea with full sail. They are amazing pieces of engineering. Nothing's square level or any other form of geometric norm. But in the main very beautiful. Not dissimilar to my wife

Make sure your wife reads this, it may prove to be to your advantage.