Okay I'll bite.
For 3 kts cruising maybe a pair of ME0913 motors (I know, I know, but I like that motor.) and a pair of 500A sine wave controllers like the Kelly KLS-D unit. Reduction ratio will depend on prop size but you can go with a belt drive and just change pulleys to experiment. The motor has a 7/8" shaft, BTW. With 16x16 props as an example you might try 3:1 or a bit less. For simplicity, a 48v bank consisting of L-16 batteries in series which are I think about 350AH but google that. Should give you usable range and weigh less than the engines and fuel tanks you are removing. These motors are rated at 72v but they will work just fine at 96v so you could go with higher voltage, but DEFINITELY consult a marine electrician because the wiring standards are different once you go over 50v. Having a genset onboard, you should make provision for recharging batteries from it. Not as simple as it sounds. You really should be prepared to charge your batteries at at least C/5, which is in the case of L16's 70A. Well we don't live in a perfect world and we don't always get what we want, but it is a big plus if your genset will do a full bank charge at a respectable rate during the bulk phase. Just sayin, because you will definitely find yourself getting dangerously low on juice sooner or later, and want to take advantage of the generator to get back to the dock.
Since you are not interested in going green, might I suggest an outboard, as a backup, to get you home when things go North? Maybe a 20HP 4 stroke on an outboard bracket, and a nice big portable tank? Used would be okay as long as it starts dependably without a lot of fuss. These new outboards usually don't require a lot of fiddling and praying and body english like the old ones. They mostly either start right up or never start at all.
Just off the top of my head I would imagine you could do this for a bit over $6k. The motors are about $750 each, controllers somewhat less. Reduction belt drive you can homebrew for about $350. You will need about $1k for couplers, adapters, cable, meters, wire, user controls, nuts, bolts, steel, etc and then there is the batteries and chargers. You will also want a nice big inverter, and DC/DC converters so you can use the bank for your 12VDC and 110VAC loads when desired. Keep the house bank as long as it is still holding a charge, and use it for an emergency power source for bilge pumping, VHF, nav lights, etc.
Better batteries will of course cost a lot more. You could go with LiFeP04s for a significant performance increase. They can be discharged more deeply than FLA batteries and should last longer. REQUIRE a BMS, though. Regular deep cycle lead batteries don't really require any special electronics as long as you do your part.
It sounds like you are a realist in your expectations. This will NOT go fast, nor far. It WILL get you out on the water where you can drop the hook and fish or sun or drink or BBQ and get away from land for a bit. Your resale value you can pretty much kiss goodbye as motorboat buyers expect a running pair of diesels. You will have endless hours of fun tinkering and experimenting with the drive system.
I was actually considering picking up an old ChrisCraft or something with dead diesels and going electric with it. Mostly just for a floating apartment that is bigger than my present one, and with enough mobility to get to the pumpout station and a few local waterside restaurants that I frequent, maybe get out in the lake with a boat bunny aboard for a night of counting stars and stuff once in a while. I decided that for me, the numbers and floor plans didn't offer much. My current boat is way too small for me but it is mine and it is electric and I can get some usable range out of my bank of golf cart batteries. So I think the idea is of only marginal or fringe practicality compared to converting a sailboat. But if you are determined, I don't see what would stop you. The boat isn't going to sink just because you put electric motors in. And the repower is still gonna cost less than a pair of rebuilt engines.
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