R.H. Marine Conversion - Gas S.B.C.

Keelboater

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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.
 

Keelboater

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Velvet Drive 71Cs. I was told that these can't be run "backwards" due to the smaller clutch size used for reverse. I would much rather do that than build a R.H. motor. But the trannies are fresh, and it is what it is.
 

F/V First Team

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Indexing the transmission pump only changes what the input rotation is needed, the output shaft rotation stays the same. That way you can run a left handed engine in place of a right handed engine. Just turns the pump the other direction, still locks up on the front clutch as normal.
 

Keelboater

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Jeezz Travis, I was looking forward to ripping this crate motor apart. Now your gonna ruin that for me? :D 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.
 

Keelboater

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Found this on line:

Rotation Guide


For the 71C with 1.52:1 reduction, the pump MUST be indexed for motor direction, BUT the output direction is always the same as the input direction. Sounds like I'm stuck with a motor tear down. But I will talk to Chris tomorrow. I'm changing the cam, oil pump, and oil pan anyways, so reversing the pistons at that point isn't too bad if it does come down to that.
 

RT46

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can you sell the motor you have?

and buy a reman 350 from one of the reputable rebuilders.
 

Keelboater

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I could probably sell it, but it's not that big of a deal to me. I've built a few Chevy motors in my day. Everything is brand new from GM with the exception of the marine cam. Same as the port engine. Easy Peasy as a wise man around these parts says. But first I will confirm if the transmission idea will work. That would be the simplest solution.
 

Keelboater

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Velvet drives with 1.52:1 reductions must have the pump indexed for motor rotation, but the output shaft will always turn in the same direction as the input shaft. Also, they can not be run backwards (with reverse = forward) because the clutches are too small. So it is what it is and I need the R.H. rotation motor. Today I swapped the pistons so the notches are facing towards the rear of the block and the wrist pin offsets are all correct. I also confirmed with Mercury Marine that the crankshafts for R.H. rotation and L.H. rotation are the same part number and there is no difference between them. I tore down the old R.H. motor and confirmed this fact in the process. There is alot of B.S. on the internet regarding "reverse grinding" the crankshaft for a R.H. rotation motor. Some of the things that I read were pretty funny, but were not intended to be. They can't put anything on the internet that isn't true, right?
 
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