Repowering
Two years ago I unceremoniously tossed the stock Yanmar YSM-12 -- what a piece of, uh, er, junk! -- overboard and replaced it with a Bukh (boo-kuh; Danish) DV24me 24hp diesel. Start to finish, $8k including the engine, yard time, some things I wanted to change, cleaning the tanks, bearings and prop. Power is a function of going from the flywheel to the Jesus nut and getting the most efficient combination so the max hp goes to the prop. You can typically expect to lose roughly 30% of your total hp by the time it all gets to the prop. It's one of those "laws" that governs things. I spent $3k of the $8k having some very talented guys install the new engine, do all the hook ups etc. At roughly $60/hr, they spent 50 hrs. getting it all done including pulling the old engine and putting in the new. I felt like I got a fair deal.When you repower, you are tossing out EVERYTHING that once was and re-inventing the wheel, so the factors change with hp.Ed's a pretty smart guy, but I think he kinda missed this a bit. First, sure, more hp and you can swing a bigger wheel but ONLY if you have the clearance to do it! In fact, more HP almost demands a bigger wheel, but you have limited space under the water and that's constrained by prop diameter and clearance. You don't want to encroach that clearance or you will find that the non-compressiblity of water will "pound" your hull and reduce your efficiency. I borrowed a principal from aviation and have a "winged" prop on my 78h30. The winglets at the prop tips create a "ducted fan" that recovers energy at the prop tips, reduces cavitation and puts more energy back into the push. Email me at bhowie@txucom.net if you are interested in this. The props are readily available.Overall, I think you got your money's worth and a fair deal.