Repowering from a MD-11C to a Westerbeke W38B
Mike and Joan Doucette (KINDRED SPIRIT) write that they have replaced their old Volvo MD-11C with a larger Westerbeke W38B (37 HP) which required only slight modifications to the front engine beds - increasing their size since the center to center dimensions of the new mounts was less than the Volvo. On the rear of the engine they had new motor mounts fabricated which aligned with the existing rear beds so there were no modifications there.
With the engine change they had to increase the water inlet to 1", change the exhaust system to 2", add a new waterlift muffler and install a fuel return line to the tank. Since the new engine was only 1/2" longer than the Volvo, but does not have the large flywheel, they were able to locate it slightly more forward giving additional room at the stuffing box. It also meant they had to have a longer prop shaft. The overall height of the new engine is less than the old, providing better access to the engine rear.
After researching new props (since the new engine is right hand and the old left hand rotation), they decided to increase the prop to a 15" diameter X 11" pitch. The old prop was 13" diameter X 14" pitch. This meant the aperture needed to be increased to fit the larger prop. They cut 1" top and bottom of the aperture and reshaped the area and then cut a slight notch in the rudder which allows the prop to be removed without moving the shaft. The whole area was reglassed and barrier coated.
This installation was done over the 96-97 winter and the boat launched in May 1997. After a few alignment changes, the whole thing settled nicely into place and ran well all season. The performance difference is tremendous: in addition to how having hot water since the new engine is fresh water cooled, they are now able to cruise easily at 6 kts at 2500 engine rpm (red line at 3500 rpm), which leaves a lot of power reserve when needed.
If anyone is interested in an engine replacement and would like more information, they should get in touch with Mike and Joan, as they have a lot of good tips on the installation.