Keelboater
Admiral
I have a new 350 crate motor that I am converting to R.H. rotation for the starboard motor in my Bertram. There are sevral changes that must be made to it, some of which are not very obvious. This is what I have come up with:
1) The cam is gear driven instead of using the timing chain. The cam will rotate in the standard direction for driving a stock distributor gear and oil pump, but the crank will rotate in the opposite direction.
2) The cam is a special grind for opposite motor rotation.
3) Special rear main seal and timing cover seal are required. They have the tiny "oil direction grooves" facing in the opposite direction. This directs oil back towards the oil pan. (How many boats have leaky rear mains on the starboard side only after repowering?)
4) The stock dished pistons have a wrist pin offset and intended thrust face, and as such are installed as L.H. rotation only. That is why they have marks on them to face forward. To use them in a R.H. application, they must be removed from the connecting rods and rotated 180 degrees. For R.H. rotation, this puts the wrist pin offset in the correct orientation as well as the thrust face. The marks will now be pointing to the rear of the motor. (How many boats have had starboard motors fail prematurely after repowering but the port side is fine?)
5) The starter motor is special for R.H. rotation.
6) Water pumps are bi-directional, but the raw water pump may require a slight internal change according to the instructions.
7) Alternator is bi-directional.
8) The crank shaft is not different. Many think it has different oil passages, but it doesn't.
9) The oil pan has the dip stick on the opposite side so it faces the centerline of the hull.
I think that's it. Has anyone else converted a motor from L.H. to R.H.? Probably a dumb question on this site with single screw boats dominating, but everyone has their past stories to tell.
1) The cam is gear driven instead of using the timing chain. The cam will rotate in the standard direction for driving a stock distributor gear and oil pump, but the crank will rotate in the opposite direction.
2) The cam is a special grind for opposite motor rotation.
3) Special rear main seal and timing cover seal are required. They have the tiny "oil direction grooves" facing in the opposite direction. This directs oil back towards the oil pan. (How many boats have leaky rear mains on the starboard side only after repowering?)
4) The stock dished pistons have a wrist pin offset and intended thrust face, and as such are installed as L.H. rotation only. That is why they have marks on them to face forward. To use them in a R.H. application, they must be removed from the connecting rods and rotated 180 degrees. For R.H. rotation, this puts the wrist pin offset in the correct orientation as well as the thrust face. The marks will now be pointing to the rear of the motor. (How many boats have had starboard motors fail prematurely after repowering but the port side is fine?)
5) The starter motor is special for R.H. rotation.
6) Water pumps are bi-directional, but the raw water pump may require a slight internal change according to the instructions.
7) Alternator is bi-directional.
8) The crank shaft is not different. Many think it has different oil passages, but it doesn't.
9) The oil pan has the dip stick on the opposite side so it faces the centerline of the hull.
I think that's it. Has anyone else converted a motor from L.H. to R.H.? Probably a dumb question on this site with single screw boats dominating, but everyone has their past stories to tell.
I will do some more research on this. I'm sure you are talking from experience, so it sounds very promising. I have 71C's with 1.52:1 gears. I will call Atlantis Marine Gear tomorrow and ask Chris about this. It sounds like a simple job if it will work.
