Engine Alignment

[moe_1200]

Looking for some help/advice on prop shaft & engine alignment on 1981 Catalina 30 with a Universal 5411. I understand the general procedure of rotating the shaft and using a feeler gauge on the shaft coupling to the transmission.

However my problem is that the boat was fitted with a flexible coupling from Federal Marine Transmissions (https://federalmarinemotors.com/how-it-works/). Their instructions for engine alignment specifies to use the original rigid coupling to perform alignment then remove the rigid and install the flexible coupling.

Unfortunately the rigid coupling that came with the boat is long gone as I'm the second owner. I'm going to reach out to Federal Marine Transmissions to get their input but my question is if anybody knows of a way to align the shaft using a different method? Or if someone has a resource where I could potentially find a used rigid coupling and if so could it be used without machining for concentricity to the shaft? I don't necessarily want to spend the the $300 for a brand new one from Catalina Direct +machining as I'd like to keep using the flexible coupling after alignment.

 

[dmax]

A new coupling would need its face machined to ensure it is perpendicular to the shaft, if not done the alignment would be suspect.

 

[moe_1200]

A new coupling would need its face machined to ensure it is perpendicular to the shaft, if not done the alignment would be suspect.

That makes sense, I probably wouldn't be gaining anything by buying a rigid coupling without ensuring it's machined to the shaft.

So unless there is another way to do it I'm probably getting a whole new rigid coupling machined to the shaft.

The boat is getting hauled in a couple of weeks and I was going to pull the shaft to make sure it's not bent, replace the cutlass bearing along with the hose between the shaft log & packing gland. Alignment would need to be done next spring anyhow when it gets launched again.

 

[dmax]

Sounds like a good plan - I know MaineSail (Marine How To - DIY for Boaters - Marine How To - incredible site for information) is not a big fan of the flexible couplings.

 

[dmax]

When you align it, follow these instructions (courtesy of Ralph Johnstone), worth doing:

 

[moe_1200]

When you align it, follow these instructions (courtesy of Ralph Johnstone), worth doing:

Nice! That is super helpful. I just looked at the Marine How-to website as well there is a lot of good information there as well. I couldn't find anything regarding flexible couplings though. What is the general reasoning against using the flexible couplings? If there is good reason to avoid using them it makes buying the rigid coupling to replace it a bit easier to accept.

 

[dmax]

Actually, I asked MaineSail specifically and he said he wasn't a big fan (so I didn't go that route). The thing is, if you get the alignment right, you don't need a flexible coupling - I think MaineSail worries that it masks problems. There's an excellent article on prop shafts you should read: A New Prop Shaft - Marine How To

If you find the site useful, consider making a donation - MaineSail is very generous with information and he is incredibly knowledgeable.

 

[moe_1200]

Thanks I will keep them in mind, the more resources the better. The fact that you have to remove the coupling and swap out to a rigid to do the alignment is probably enough to make me not a fan either.

Federal Marine transmission specifies their unit is designed to overcome only slight misalignment. I think it's more designed to take out vibrations to protect transmission bearings. I suppose that's worth something.

 

[Ralph Johnstone]

The fact that you have to remove the coupling and swap out to a rigid to do the alignment is probably enough to make me not a fan either.

I would think that the flexible coupling has a very specific use :

A. The user is a lazy sot.
B. There is some inexplicable reason the the last bit of misalignment can't be removed. I haven't been able to come up with one yet. Maybe the hull is inordinately flexible. Think rubber.

I think the flexible coupling is an invention for which there was never a need .

Because you seem so conscientious and want to do it up right from the start, I'd suggest turfing the flexible coupling over the side and installing a properly machined rigid one and feel the satisfaction of getting it down to +/- 0.002" angular. It's an SOB to get it right but the feeling of satisfaction lasts quite a while.

I look at mine maybe every 4-5 years if I'm lucky and have only tried to improve it once after receiving and then correcting it from the factory at 0.012" angular misalignment. I'm still at 0.002" angular after this time. It doesn't change much once you've got it. Vertical is also good in spite of everyone jumping up and down and wanting to renew their motor mounts after every use of the boat because the motor mounts compress. Not that I've seen. Mind you, all my mounts are spotlessly clean because I lost a rear starboard mount after about five years because I had a hidden microscopic fuel leak over it. I didn't like the look of it so out it came. Once bitten, twice shy. THAT was the mother of all jobs as I didn't want to remove the engine in the middle of a Vancouver winter. We hold all sorts of records for miserable rainfall. Definitely specializing in miserable.

 

[moe_1200]

I look at mine maybe every 4-5 years if I'm lucky and have only tried to improve it once after receiving and then correcting it from the factory at 0.012" angular misalignment. I'm still at 0.002" angular after this time. It doesn't change much once you've got it.

I'm on the Great Lakes so it gets hauled and launched annually. Hopefully once I get it right it's stays aligned for a bit but I'd have to imagine the 7-8 month stay on the hard and then refloat is going to make some things move especially if the mast gets stepped (which it was this year).

I think it’s going to be on the annual inspection checklist, even more reason to ditch the flex coupling.