Conversion from Marine V-8 to 4 cyl diesel.

I have a nice 1988 20’ Shamrock Walk-through with the original Ford Pleasurecraft Marine 302 V-8, with a Velvet Drive AS-71C transmission. The boat has hard chines and a keel, but it is NOT a deep Vee hull. I am considering (Actually, I may have no choice) a repower; and am looking at a Volvo D2-60 or a D2-75. This engine swap would save me over 450 lbs, and I would gladly give up the 30+ mph top speed for a much quieter ride, and a top end in the upper mid teens. Back in the late 1940s and early to mid 1950s, 60-80 hp in-line 4 cylinder and 6 cylinder engines were commonplace for 16’ -20’ boats of about my same displacement (2,500 lbs after re-power). At one time, there were some on-line calculators about engine hp, torque, displacement, and prop size. By way of comparison, a NEW Matthews ‘22 Bay Cruiser with a Yanmar 100 hp 4 cyl with a hull configuration similar to mine, makes 22 knots. I don’t see a down side to doing this, but I’m curious if anyone else has done a similar swap.

 

Welcome to the Forum Capt Ted.

I know a chap here who has a 1996 centre console Shamrock 20 - when he first got her about 10 years ago she had a GM V-8 275 hp petrol engine, and 2 years later he refitted her with a turbocharged 4 cylinder diesel Yanmar 4JH producing 110 hp, and he has been very happy with her ever since.
He had to buy a new propeller, but I think that was about it - I think they still have the same shaft and stern tube.
Edit - and I think he had to do some modifications to the beds, but not a lot.

 

I would like to marinise a hyundai r model 2.0 diesel from 2011 onwards hyundai and kia suvs. Lovely little diesel that put out around 180 hp.