replacement for Bukh diesel

Be very careful converting an outboard gas motor. Outboards aren’t meant to be inboards. That lack such important safety features as flame arrestors. You’ll need to install a blower.

Here is another idea for you if you are unable to fine an engine. If you look at the sail drive, it is really just the bottom end of an outboard motor except that it has no cooling water intake nor exhaust. However an outboard engine power head of similar size joins to its lower unit in just the same way. On the Bukh the sail drive unit attaches to a hollow aluminum intermediate casing the captures the double rubber hull seal between the sail drive and the power head (engine). Four bolts come through the base flange on the sail drive, the double seal, through the casing and into the bottom plate of the power head (engine). So......find say a 4-cycle outboard power head that is perhaps in the 10hp range, fix a 3/8" aluminum plate to the bottom of it with a hole allowing its crankshaft to come through its bottom, and shim it so that the crank shaft aligns with the drive shaft of the sail drive. Any machine shop could make the drive cog for the bottom of the shaft to match that of the Bukh sail drive. Drill and tap the bottom of the new plate to take the 4 nos. 12mm stainless steel bolts that come up through the sail drive and screw the new power head to the old sail drive. The remainder of the challenge is fixing a cooling water pump to the engine but that could be driven from a 3" diameter pulley mounted to the top of the new engine's flywheel.

The system would run on gas, but would be quite economical and smooth running as a 4-cycle, and would save about 50 lbs of weight. I have seen such power heads from Mercury, OMC, and Nissan on Ebay for just a few hundred dollars. It would be a fun project and very simple.   Just look at the top of the shaft on the sail drive you have and you will see that it is not difficult to make the part to engage it to any powerhead that will fit into the space. it just needs the conversion plate so that the sail drive bolt circle will match up to it.

stumbled on a site that advertises Yamaha SD 330 saildrive. In Canada it is sold by Marineoutfitters.ca. May be of help to you.

Personally I love the Bukh and encourage you to find one. Might not be that hard. I recently pitched up at the Royal Hong Kong Yacht Cllub to be told that five of them were laying in the yard. Unfortunately by the time I enquired Thayer had been hauled to the dump. These engines were designed for use in lifeboats and once were plentiful. Also, some yacht owners gave up on them and switched to outboards owing to corrosion of the sail drive which was not replaceable. There may be some engines laying around. The Bukh is far better than the Yanmar or Volvo. Try harder to find one.