Outdrive to Inboard conversion

I know I know, its not something you hear much about, but i have always liked 2556 Bayliners, my dad had one before he got his big boat, and i can get a good deal on one with a busted Mercruiser outdrive. So i thought about what i could do with it, i like cruising slow (for fuel and engine cost) here's my idea:

idea 1) the 25 bayliner, has about a 4-5 ft engine bay, and draws 23" at the transom, so add a 3 ft hull extension and cut a gentle prop tunnel into the hull and extension. ideally would get just better than 18 degrees of shaft angle. im thinking like a 45hp beta-marine diesel for the compactness.

idea 2) same extension and tunnel, but instead of a shaft drive i could go with a sail drive:
Inboard Conversion - Album on Imgur https://imgur.com/gallery/kudiISS

 

I like a v drive and small diesel with a shaft and a stern extension better. Sb marine has done a fair bit of divorced v drive rigs and they seem to work as it allows for weight balance aft more akin to an out drive configuration.

Over the years we've had more than a few circumnavigation boats hauled at the yard. Seems like the sail drives had a shorter life span than even out drives. For longevity sake a marine transmission and shaft drive is near bullet prof if done right on a hull speed rig.

As for a labor of love be as realistic as you can about budget and the high probability of a 0 dollar return on cost. If your ok with the idea and don't mind that reality it can be a cool project.

About six or seven years ago I was looking for a nice clean little isuzu that could run a hydraulic pump for auxillar hydraulics. Was hard to find a propulsion vs gen configured engine so it took me some time. Eventually found the cutest little runabout that had been converted to diesel from outboard complete with an intricate wheel house. Some retired navy fellow had done a spectacular job on the conversion before passing. Sadly it had languished on the market for a long time and I bought it for 1500 with only about 35 hrs on the main. It was about 9 cents on the dollar of the mains price.... had it cut up and gone, the engine palatized and shipped and the trailer sold on cl less than 24 hrs after I'd bought it. Moral of the story is, make sure you can derive joy from the project and the finished work, market size may be 1...

Easy button is a long shaft hi torque Bigfoot style outboard and a bracket, but fully understand intangible reasons for other methods.

 

I would prefer the simplicity and reliability of a vee drive configuration. Saildrive is a sterndrive built lighter.

 

There is a 70's Bertram 25 here which originally had twin outdrives and gasoline engines - a few years ago she had a major conversion to a single inboard diesel on a straight shaft (ie not a vee drive), and she seems to be working well.

 

I'll never understand people wanting to modify planing hulls into displacement boats with an engine change.

 

Used mercruiser outdrives are cheap. You can run the existing engine at idle for less fuel consumption. The savings on mechanical systems will more than pay for fuel the rest of your life.

 

I would love to hear more if possible, sounds like a cool project!

 

I looked up in my records and found a couple of photos that I have of her - apologies, but I do not have any of the engine installation.
The engine is a Yanmar 4LH-5TE 4 cylinder 240 hp diesel on a straight shaft drive with a 4 blade propeller. The shaft is supported on a welded S/S 'A' bracket bolted to the hull.
The engine does take up a fair bit of space in the little cabin - it has a box over it.
These photos were taken in 2008, after a 4 year restoration by the owner - and this restoration apparently cost him approx US$ 70,000 in total, including the purchase price of the boat.






There is also a Bertram 25 here which I think used to have twin outdrives (it might have been a single outdrive), but she now has a single Evinrude 150 hp outboard engine mounted on a pod - here are a couple of photos of her.



In this photo she was estimated to be doing about 20 knots with the outboard engine.

 

The Bertram 25 was a great hull and to me the loss of space in the poky cabin from the Yanmar would be more than made up by the deck space and storage gained aft. They generally came with twin 470 Mercruisers, a bit of Mercury mastery where they built a 4 cylinder aluminium block under a single 460 CuIn Ford cylinder head and created a fuel gulping monster with a high failure rate.

 

Pretty nice fishing machine as done. Clean, open, dry underway, a place to hide from sun or rain.