plugster wrote:
I need to replace or rebuild 2 Yanmar 3GM30FC saildrives in a 43 foot
sailing catamaran. The old ones are 27 hp with the SD20 saildrive and have
about 3000 hours on them and were submerged in salt water for about 3 days.
Once removed from the water they were taken apart, washed and oiled.

Not the best treatment IMHO. They should have been washed in fresh
water, had the heads pulled & dried, oil changed, and immediately run.
BUt that's water over the dam at this point.


I think I have about 5 options. The first is to have the whole units
rebuilt.

Given the cost of rebuilding AND reinstalling them, this may not be the
best use of funds.


... My third option is to replace the whole system with the newer
Yanmar 3YM30CE version that is 29 hp. I think that this is a bolt in
replacement.

If it really is a "bolt-in" replacement then that may be the best way to
go , in terms of utility/cost comparison. I'm sceptical of the "bolt-in"
part though, it never goes that easy.

... My forth option is to replace them with the larger 3JH4CE
Yanmar with the SD40 saildrive. This is the 40 hp version and looks like it
costs about $1500 more each over the 29 hp units. Has anyone replaced the
smaller and older 27 hp unit with the newer 29 or 40 hp unit?

I personally have not. But I am somewhat familiar with a smaller
Norseman and I wonder if you have the space to install them... and if
so, will access to larger units be a maintenance headache?

... I know the
mounts are different with the 40 hp. How much added work and how difficult
is this?

Considering the fiberglass work you're already committed to, it may be
easiest to saw the sterns off, put the engines & drives in, and then
fiberglass the sterns back in place


The fifth option is to replace them with other units. Are the Volvo units
identical to the Yanmar units?

No

... Can you buy them for a better price?

???
I've never heard anybody use the words "Volvo" and "better price" in the
same sentence before.

I have a number of friends with Volvo saildrives and they all report
that the units work wonderfully but are $$$$ to maintain.

... Has
anyone had any experience with other saildrives?

Some. Yanmars probably the best.

... How difficult are they to
adapt?

If you can be casual about sawing a big hole in the hull, easy. If
you're squeamish about it, then very difficult to impossible.

... What do you think about going to V drives with a conventional shaft
and prop?

See above. You're going to have to reengineer the back ends of the hulls
to change engine configurations. I happen to like the concept of the
V-drive but have never ever seen an installation that wasn't a
nightmare. I don't know why this is.



... On all of these I have the option of fixed (about $600 each!) or
folding props (about $1400 each!!!!!) what do people like better and why?

Personally I like folding props on boats that sail fast.


How much more power cruise speed would you expect to have going from 27 to
29 or 40 hp? Most people claim the boat is underpowered with the 27 hp
engines and will do about 7 to 8 knots.

Most people are in love with horsepower for it's own sake.

IMHO it's a bad idea. You will gain 10% speed, perhaps 15%, and burn 4/3
the fuel; and that's if you carefully match the props size & pitch. If
you don't do the homework carefully (or pay an expert to do it) then
you'll gain less speed and burn twice the fuel. You'll add weight to the
boat and bury the stern. You will increase the draft. You will have less
access for maintenance. Many people think that increased horsepower
gives you better maneuverability, but remember that water is
incompressible. You just make more noise & froth. I could go on and on,
but this is probably the highlights...

Interesting project. I wonder why the owner did not keep the boat and
put back in commissionn. Good luck with it, hope to hear more from you.

Fresh Breezes- Doug King