The M135 Perkins is a great engine but I think its weight-to-horsepower ratio is too high - possibly one of the reasons why they last so long.
We considered the
Yanmar 110-hp for our 40,000-pound
ketch but it came with a ZF25
transmission which is too small for that horsepower and torque. We ultimately replaced the
Volvo MD40A with a
Beta Marine 90, which came with the ZF45
transmission. We’re delighted with the Beta and have over 3,000 trouble-free hours on it. We consume slightly less than a gallon per hour cruising at 5.5 knots. However, the naturally-aspirated Beta 90 is no longer available in the
USA (doesn’t meet EPA standards). Since I strongly feel that turbocharged diesels are a poor choice for a
cruising sailboat, I’d probably choose to rebuild the Perkins if it were my decision.
Fair winds and calm seas.