Engine Swap

[agg212]

I currently have a an 1-cylinder Yanmar YSM12 (original to the boat from 1979). I am looking to replace the engine with a newer 2YM15 that I've rebuilt myself.

I am considering trying to do the swap myself, but am wondering (1) what is the best way to modify the engine bay to fit the new (narrower) engine, and (2) how to properly align the transmission to the shaft.

 

[ggrizzard]

I replaced my YSM 12 with a 2GM20F on a H30C several years ago. All I needed to do was add insert panels to the existing runners which narrowed the mount space width by 2 inches and raised the runner elevation by 1 inch. I can't advise on alignment as each situation with different bay dimensions/shaft lengths/stern tube/exit angle/strut support, etc. are unique.
You should consult a re-power expert.