Flexible couplings, what do you really gain?

[scottie]

I think that should be engine mounts as No 3, not cutless bearing. I've never seen a 'flexible' cutless bearing mount.

Correct

 

[Poey50]

I think that should be engine mounts as No 3, not cutless bearing. I've never seen a 'flexible' cutless bearing mount.

Yes, of course, you are correct. I've edited my previous reply. My apologies for confusing (anyone else than myself).

 

[Poignard]

My single cylinder engine dances around like mad when it is running. I think it would do untold damage without a flexible coupling. It broke one coupling and I was advised that I needed one bigger and more flexible on account of the fact that I was driving my boat with a "cement mixer engine". I'm ashamed to say I can't remember the detail, but it did involve an R&D coupling with an atypical spec and an atypical price.

Have you considered fitting less flexible engine mounts?

Robush ltd could advise you http://robush.com/

 

[Amulet]

Have you considered fitting less flexible engine mounts?

Robush ltd could advise you http://robush.com/

The engine already vibrates the boat enough to loosen your fillings. Maybe a different engine. Trouble is I'm kind of attached to my Farymann. it is about as simple as it is possible for a diesel engine to be. It has never failed, can be started easily by hand, and can run even if there is total electrical failure on the boat.

 

[dougo]

very true in 50yrs of boat building never seen flexible stern bearing ,wouldn't want one myself flex engine mounts need to be wright for the engine pss seals allow for some movement flexible drive couplings a must on these motors that dance around the bilge

 

[IanCC]

The engine already vibrates the boat enough to loosen your fillings. Maybe a different engine. Trouble is I'm kind of attached to my Farymann. it is about as simple as it is possible for a diesel engine to be. It has never failed, can be started easily by hand, and can run even if there is total electrical failure on the boat.

Maybe with stiffer mounts it won't vibrate so mych because it can't. The stresses turn up somewhere though. I have a 3gm30f on pretty solid mounts and it is quiet, doesn't vibrate much.

 

[davidmh]

I have fitted a couple of R&D couplings and was told by a very experienced engineer that what you should do is to start by pulling the shaft forward and mating up the solid flange of the gearbox the solid flange of the shaft. Adjust the engine mounts until the fit is good and the shaft is in the centre of the shaft tube. The two flanges should fit with the male spigot fitting into the female socket with no movement. Feeler gaps around the flanges should all be the same. Rotate the shaft and check fit in a number of positions. You then lock all the mounts and slide the shaft back and insert the R&D and bolt it all together. The R&D as others have said is not really a flexible coupling in the true sense and will not compensate for misalignment problems.
David MH