I've heard nothing but good things about the Yanmars, aside from cost, and
my experience with ours certainly bears them out. At 27 years of age it
feels like one of the sweetest running pieces of machinery I've been
associated with. I certainly trust it a lot more than the engine I used to
fly behind

It would be worth having some prop calculations performed. There is no
point in putting in a 3 cylinder Yanmar (or other engine) if your prop can
only use the horsepower of 2. The 3 cylinder will be a bit smoother but the
2 cylinder, 2 blade, installation in our boat is plenty smooth. Diesels,
especially Yanmars which are a cool running engine, will give more trouble
running too lightly than at their rated continuous horsepower. After you've
paid for a cylinder you don't need, you then have the reduced maintenance
clearance and extra weight for life.

The power requirements of your Bristol should not be very different than
Strider and I have all the power I need. I was able to keep moving straight
into the wind during a squall that heeled us under bare poles to our normal
sailing angle. The sail cover was thundering and the rain hitting my face
stung. I don't think you need much more power than that unless you plan to
tow a barge.

--
Roger Long