Volvo saildrive diaphragm

[Srah 1953]

It used to be the case that Yanmar saildrives had a double rubber diaphragm while Volvo Penta had a single diaphragm. Is that still the case? I'm particularly interested in a Volvo D 50 with saildrive.
Thanks

[Srah 1953]

Also, on another thread it's stated that you can't fit a rope cutter on a Volvo. Is that correct?

[AllenRbrts]

I have a 130 drive on d2-55 It has a single diaphragm. I have line cutters on my maxprops. Line cutters are very prop dependent.

[Srah 1953]

Thank you.

[belizesailor]

Originally Posted by Srah 1953

It used to be the case that Yanmar saildrives had a double rubber diaphragm while Volvo Penta had a single diaphragm. Is that still the case? I'm particularly interested in a Volvo D 50 with saildrive.
Thanks

Still the case to my knowledge. There are parts diagrams available online to confirm specific models.

[Srah 1953]

Thanks

[belizesailor]

Note that its rare to have a bellows (diaphram) failure in either design. There is a thread here on that subject I think.

The Yanmar version has a water sensor between the 2. It is prone to malfunction. Ive been aboard lots of boats where it is disconnected due to frequent false alarms.

[Srah 1953]

Thank you.

[Muaddib1116]

If the diaphragm surrounds the saildrive's mounting spot to the hull, how is the thrust transferred to the boat? through the engine? Or through that little tab behind the saildrive? Or a combination? That tab doesn't look particularly robust, as far as fore/aft thrust loads are concerned.

[AllenRbrts]

Originally Posted by Muaddib1116

If the diaphragm surrounds the saildrive's mounting spot to the hull, how is the thrust transferred to the boat? through the engine? Or through that little tab behind the saildrive? Or a combination? That tab doesn't look particularly robust, as far as fore/aft thrust loads are concerned.

I don’t think the bellows (aka diaphragm) supplies much mechanical support, most of it is from the engine mounts, the rear one being the “tab” you refer to. I have heard of stories about saildrives being ripped from the boat from collisions or getting a dinghy painter fouled, leaving a large hole.

[DougR]

Originally Posted by Muaddib1116

If the diaphragm surrounds the saildrive's mounting spot to the hull, how is the thrust transferred to the boat? through the engine? Or through that little tab behind the saildrive? Or a combination? That tab doesn't look particularly robust, as far as fore/aft thrust loads are concerned.

The Volvo engines are supported by three mounts, one on each side at the “front” and one on the saildrive at the rear. All three transfer thrust from the drive into the engine bed, which is glassed to the hull or incorporated into the hull liner which is then glassed to the hull.

The diaphragm doesn’t carry any of the saildrive weight or prop thrust.