What size motor? 40" steel

I have a 40 foot steel hull sailboat. It is a rounded hull 3.6 wide. Draft about 6 feet What rpm would a sailboat motor be recommended to run @ High torc low revs say 1500 rpm?

Also if I was to have an auxilliary motor how would a 75 hp outboard be?

 

45 to 54HP would do the trick...

 

Thanks heaps. I make biofuel from used cooking oil and there is a percentage of the fuel that needs to be heated in order to use it. I want to run a generator with it. Most descent generators that last are designed to run around 1500 rpm. Is that compatable with the boat because the hp is compatable for the size generator i need. Them when I'm ready and the boat is nearly finished I can put the generator motor in the boat.

 

RPM's on engine

Gensets run 1500-1800 rpm's often to meet the Htz.

For your boat without much more information I would say a Yanmar 3JH4 or a 4JH4. Yanmars are biodiesel compatable along with Cummins. Cummins is in the biodiesel powered Earthrace, but they don't make small yacht engines.

 

Nice, i googled both models. Thanks for that.