Originally Posted by jleonard
I for one believe you will benefit and like the additional power.
I have experience in powering up" an old boat. I had an old 34 Mainship and replaced the original anemic Perkins 160 with a Cummins 6BTA 270 and the additional ponies made a great boat an outstanding boat.
Originally it was an 8 know cruiser, topped out at 10.5.
After the repower it cruised easily at 13/14 knots and topped at 18.5.
And for those many times I cruised at the "original" 8 knot pace I got about 50% better economy measured in nautical mile per gallon.
I say power up.
Makes a huge difference what hull one is powering up. Leonard's M34 has a very straight and w flat bottom at the transom. Narrow entry fwd kinda like a big wedge. Great for 20 knots .. maybe even more depending on weight.
But adding power to a CQR for example won't get you much beyond a big wake. Don't know the hull in question but it's probably not nearly as good as the M34 for more speed. If it has a straight run aft and not too much weight Leonard's comments are at least applicable if not spot on.
I would say to the OP find some other boats w the same hull as his and w more power and inquire as to their performance.
Lots of variables can make repowering fairly economical but I would make serious planing and cost estimates first.
But faster boats don't sell well so the OP selling and buying a faster boat could be quite economical. "Flip'in" boats is not a common pastime but if your a good salesman and like detailing ....