Unfortunately, those wouldn't work for my older Max-Prop (i.e., no zinc nose cone). Plus they don't seem to have a lot of zinc volume, so might need no-doubt inexpensive replacement fairly often. They are pretty nice otherwise, but a shaft zinc seems more practical, even if requiring a bit more shaft space.
I called R&D Marine. Phone was answered right away by someone who knew stuff, so that felt good. Short version from R&D is that for lower power/smaller flanges/smaller shafts keying is optional but not standard. That included us at 50HP/4in flange/1in shaft. He also said some folks still go with no key even on the larger shafts to add a bit of safety factor - if something goes bump shaft spinning may be preferable to not.There are clamping non keyed coupler applications, I can only speak to what I used , the RND split coupling which required a keyed interface for our engine and drive line, 100hp engine with 1 1/2" shaft. If it is designed for the keyway to transfer load and there is no key it will slip under load and perform some expensive in place machining and welding. I have no idea if they have a product range that does not require the keyed interface, something you will need to get from the manufacturer.
Geez @Rasputin22 . I knew you had trouble on the trip down, but the trip home was that bad too?Hello Occam,
When I delivered your beautiful cat from the VI to Newport many years ago, it was the shafts that gave us the most trouble. The shaft on one side came out of the coupling but the prop got hung on the rudder. I'm surprised we didn't lose the shaft! It was pretty nasty conditions and we were about a day out from landfall in Bermuda and it was no easy task getting that sorted out. Lots of vibration and the other side was almost as bad but I have blocked out a lot of that bad experience. Someone above mentioned shaft length and flex in the hull itself causing alignment problems and think that might be a good thing to look into. How to go about is another thing though.
I have installed BIG Centa thrust bearing/flex units on a big Gold Coast powercat with a big hollow primary shaft to the thrust bearing and then an an Aqualloy solid shaft. The clamping action on the smaller diameter solid shaft going to the propellor was very similar to a router collet and had no keyway. One can really torque down on those sort of collets and I can't imagine one ever failing. I have also installed the PYI's in far less demanding situations. CENTA and PYI staff are both excellent though. Good Luck!
rigid mounts on a gm are fine as its a 2 stroke, very smooth runningI've just taken over running a 42' ex-fishing boat that's been converted into a research boat. It's got a detroit diesel 4-71 on soft mounts, and has a history of drive train issues - they've had to rebuild the transmission every 5 years for at least the last 10 years, maybe longer but don't have maintenance logs going back that far. It also seems to be chewing up cutlass bearing pretty quickly (500 hours or so), even with the engine perfectly aligned at the dock. The previous captain strongly suggested that we convert it to rigid engine mounts, but he wasn't able to get that done at the last haul-out for a variety of reasons. Currently there is not a flex coupling on the shaft. Is there any reason to think that putting a flex coupling in is a better option than rigid mounts, either in terms of cost or ease of use? I've only ever interacted with sailboats with flexible engine mounts, shorter shafts, and less torque-y engines, so the whole rigid engine mount thing is a totally new world for me. Are they something you normally just get fabricated, or do people sell them like they do fixed mounts?
Looks like it did its job of absorbing system flex. I don’t see the problem; replace it. And maybe your engine mounts and cutless bearing too.R&D coupling for 50hp and 1.25" shaft, deformed after 5 seasons use. R&D didn't have a good explanation and offered a big discount on a replacement. No thanks. They also said the coupling is primarily intended for impact protection, not for reducing vibration.
View attachment 555352
Some kinda saddle bearing ….used to stabilize a long shaftDoes it make any difference in this discussion that there's an intermediate shaft bearing that's about halfway between the cutlass bearing and the transmission? Not sure what's inside of it, but the outside is bronze, the alignment of it is adjustable, and it is greased heavily. If everything is aligned right, when the engine moves it on its flex mounts it should be wearing out that bearing as well, no?