Re: Repowering Bertram 25?
First thing, the existing engines are shot. They're 44 years old, salt water cooled. The carburetors are fairly recent, but both need new ex mflds and risers. The problem isn't rebuilding the blocks. It's that all the ancillaries are old and tired. Replacing the generators, starters, carbs, fuel pumps, mflds, and adding on heat exchangers would cost a lot.
Second, this exact boat will in fact go 5 kt with a 15 hp long shaft evinrude. I've done it on another Bertram 25, taking it from Islesboro Maine to Thomaston, Maine, a trip of about 35 nautical miles At that speed it isn't making waves at all, and it's square transom isn't causing much turbulence, so it's really just skin resistance. The only thing that would change the picture at all is weight, because the boat I'm talking about didn't have the outdrives installed. It's a long story.
Third, a Bertram 25 isn't a wooden boat. They're an early fiberglass boat, with what might be the first deep vee hull ever put into production, following the success of a Bertram boat (called "Moppie" maybe) in the Miami Nassau race, which was a big deal back then. Some people think these are classic boats, worthy of all sorts of trouble and expense.
Finally, I don't see single screw as a problem. I've been employed running tugboats as captain for the last eighteen years, and have only worked on two twin screw boats. All the long trips, like New York to Puerto Cortez Honduras to New York have been done in single screw boats. My experience sailing as engineer on fishing boats, coastal freight in Alaska, and coastwise tugs was entirely in twin screw boats. Other than a twin screw passenger boat I used to own, and a six month stint spent operating a bunch of twin and triple screw US Navy vessels, and a recent trip running a twin screw square topsail schooner around England and down to Portugal, I have spent very little time in multi-screw boats. My observation is that single screw boats maneuver as well if you're on top of it, and if the engineer is good they don't spend any more time floating around dead ship.
If I understand the collective wisdom of the group here, it is:
1) Stay away from OMC electro-matic shift!
2) Volvo might be a better choice than Merc for a medium-speed boat
3) Diesel would be better than gas, cost no object.
So the next question is, where's the best place to look for a running-takeout Volvo duo prop? The idea of looking for a damaged or totalled boat to take an engine out of has occurred to me.
