The Repowering of a 1978 Mainship Type I
The Mainship Type I trawler debuted in 1977 and our boat came out in 1978. This model came with a Perkins Turbo charged 160 model T6.354. A good engine to be sure and ours provided great service for many years. However late in the summer of 2006 the engine did fail and became bound. We had this engine pulled and rebuilt once years ago and so we did not want to go down that road again. Thus repowering!
Engine Removal; This section provides details on our effort to remove the old engine. The Mainship Type I has the engine access inside the salon. This is good if your working on the motor on a rainy day, but for removal it does present some challenges.
Engine Selection This proved to be a lot more complicated than we thought it would be. The biggest wrench thrown into the decision was that Cummins no longer made the 6BT, their line now is the QSB.
New Engine Placement The new engine was brought in the same way the old one went out; with a large crane. There are a few mistakes we made that can be good lessons for others here.
Motor Mount Redux! We made some mistakes the first time we installed the new engine, so in year two we re-did them!
Engine Bed Stringer Reinforcement The original engine bed stringers were 1.5 inches thick and we upgraded them to 3 inches thick. This is an important element and there are a few mistakes we made here you can avoid.
Replacing the Fuel Tanks When we were working on the re-power we noticed some fuel pooling in the bilge. After a long search we discovered fuel was weeping from the port tank; so out they came.
Replacement of the Floor Because we had to remove the floor to remove the fuel tanks a new floor had to made. It’s quite possible during a re-power you would not need to do this. However, we wanted to make our engine access better, so we made new and bigger engine hatches.
Upgrading the Raw Water Intake The old Perkins was fed raw water through a 1 & ¼ inch sea cock, but the new Cummins will need a 2 inch sea cock. Also, there was quite a debate on how to filter the raw water.
Exhaust System The old Perkins exhaust system had just a 4 inch hose running from the engine to the outlet at the transom. For the Cummins we had to increase the hose size to 6 inches, install a muffler, check valve and replace the exhaust flange.
Running Gear The old Perkins had a 1 & ½ inch bronze shaft which we had to change to a 1 & ½ inch stainless steel (Aquamet) shaft. Plus we replaced the cutlass bearing, mid bearing, prop and installed a drip less stuffing box.
So long old buddy!
