My Endeavourcat 44 has two yanmar SD40
saildrives. These saildrives do not have the best reputation for reliability
and were superceded by the SD50
model after only a few years on the market. The biggest reliability
issue seems to be the cone clutches on this model though I have personally not had any problems with the cone clutches at about 1300 hours. I probably should not have said that and will have a cone clutch
failure next time I start the things, so knock wood. I have had two issues with my saildrives. The first was a prop shaft seal
failure precipitated by getting some monofilament line wrapped around it in the ICW
. Just like outboard
engines these prop shaft seals are vulnerable to being cut by monofilament line. The second was I had a front main seal failure on the transmission
section while in the Bahamas
. This sprayed about a quart of 90 weight oil around my engine room over about a 4 week period. Both of these failures happened on the same trip on opposite drives so I did not have an option of not using the problem drive. When I got back I had the boat hauled to repair the drives. Sourcing the prop shaft seals in the US was a problem, they wanted me to wait on the hard
for 3 weeks while they were shipped in from Japan
all the while running up yard charges to the tune of $44 a day. I got on the internet
and had them shipped overnight from the UK for $35 shipping
. I paid the exact same amount after currency conversion that I would have paid in the states plus the shipping
or about $55 a piece (2 required). I noted when I got them they were standard 34x52x8 mm viton shaft seals. These are available from a local supplier for about $4. The main shaft seal
was not so straight forward. The spring in the failed seal had worn a groove in the pilot shaft and that also had to be replaced. It seems that the springs in the seals are much harder than the shafts and if you run them for any length of time after the seal fails you are likely to damage the shaft beyond repair. Technically the front main seal repair could have been done in the water
by moving the engine forward about a foot.
While they were out I had the hull
seals replaced as they were 6 years old and replacement was recommended at 2 years. I also had the hull boots replaced as they were also 6 years old and pretty ratty looking. A previous post on this thread may have suggested that the boots are the seal, they are not! The boots meerly streamline the hull opening where drive passes through the hull. These boots accumulate a lot of fouling as paint
won't stick to them. Scraping the fouling off tends to damage the boot over time. It does not affect the drive seal. The double drive seal is located up in the hull at the saildrive
mount. Note that after 6 years in the water that there were no barnacles
or any other marine
growth on the primary seal. In fact I was hard pressed to tell any difference between the seals being removed and the ones being put in. I kept the old seals as spares though I can't imagine these things failing as they are quite heavily made. It seems to me that replacing them after 6 years was probably a waste of money
and replacing them on a two year cycle as Yanmar recommends is insane.
Changing the oil in these units is a pain and requires vacuuming the 90 weight out from the bottom of the unit when in the water. Despite having a tube that goes to the bottom of the unit, 90 weight does not readily flow when cold. And actually getting all the oil out takes several stages of pumping, allowing the oil to settle to the bottom of the unit, pumping again, etc. It usually takes 4 cycles on each unit to get all of the oil out, each time allowing an hour for the oil to settle. This makes changing the oil on both drives an all day effort. When the boat is out of the water it is a simple matter to open the drain on the bottom and the vent on the top and drain it into a bucket for about an hour.
Another issue is changing Zincs, I have autostream props which means that standard zincs don't quite fit and need to be filed down. The split zincs (available @$250 each) that are supposed to be changable without removing the prop don't work either so zinc changing is a special problem for me. A standard folding prop would be easier, at the sacrifice of reverse thrust.
As for the example of the cat that lost
its saildrives in the collision
with the whale, my understanding is that there was no water intrusion outside of the engine compartments and the collision
had not put the boat in jeopardy of sinking. The problem was that the collision had destroyed the rudders as well and the boat had no steerage and that was the reason she was abandoned. I suspect that the same thing would have occurred with a shaft drive and the boat would still have been abandoned.
I guess the question is would I trade
my sail drives for shaft drives and I believe to be honest I would say yes. Would I not buy a boat just because it had saildrives, no. If you look at Endeavour's web site it appears that they now supply shaft drives on their new boats. I'm not sure if this is because of reliability issues or because it allows them to use the same molds for their power cats and sail cats.