I own the same ship, a 1977 boat, currently with a Volvo MD17C.
The next motor is likely to be the Kubota-based Beta Marine 38 hp or 42 hp.
Be careful though, the Kubota turns the prop the other way from my Volvo, so if your motor is the same rotation direction as the Volvo, you will need a reversing gearbox, probably with an oil-cooler. Ask the supplier if the reversing box is more noisy than the present system.
I like the idea of the Kubota, as it will have the usual Japanese quality typical of their motorcycle engines.
The Kubota motor will probably be revving higher than your current motor, so be careful with your gearbox ratios.
I would advise you not to put a Volvo in there. The motors are OK, but the price of the major spare parts are not remotely reasonable. They really are far too expensive.
I have just started my research and know nothing till now. If I can afford it I plan to change the complete drive line engine,tranny, shaft, stuffing box and prop etc. I am not sure but if the prop and tranny are designed for the correct engine rotation would it matter to the boat? Did you consider the Yannar? Any ideas on cost?
Why not rebuild your current engine? Returning it to new will be lots of boat bucks and lots of work less. If you do it yourself, possibly with a babysitter if you are inexperienced, you will gain a huge measure of satisfaction and knowledge (and a few new tools ).
Changing engines can be a brutally frustrating experience, even if access is not a problem.
Failing that, I'd enquire about engines that fit the same footprint.
Thanks, I will investigate further on the rebuild. I was told that it is getting tough to find parts for the old engine. I also hope the someone has already blazed the trail and I can avoid some of the frustration.
I would contact a Westerbeke dealer and ask about parts availability for a rebuild. I have found Westerbeke parts to be quite available, but not cheap. Westerbeke have changed their parts numbering system. You can download a parts manual and a service manual (I think it has the rebuild in it) from the Westerbeke site, but the numbers will be different than in the manuals.
You haven't said why the engine is dead. If it's just real tired ,a set of rings and bearing shells could be easy. If you decide to do it this way, good to mike the bores and crank before you order parts.Then send the head out for valves.
Read Porfin's (unfinished) thread on rebuilding his Perkins. It will give you a very thorough picture of what will need to be done. If you take your time and don't cut any corners you will end up with an engine that is better than new and for a fraction of the price of a repower.