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M-Funf
05-22-2007, 11:06 AM
I'm looking to purchase a new prop soon, and have some questions.

- My '76 S&S has RH rotation. I was told that most MC's are LH rotation. Is something different about my boat? Did they make RH rotation in '76? Was my boat repowered with a RH rotation engine and re-propped?

- Which side of the rudder should the shaft be biased to on a RH rotation prop? (this might help me determine if the boat was repowered)

- My 3 blade nibral prop (13X13) seems to be in O.K. condition, but I do have some vibration at a couple of different RPM's. I'm hoping that a new prop reduces or eliminates this vibration.

- Should I replace the strut bearing/bushing at the same time? Or should I just do the prop first, and then the strut bearing if I still have a vibration? (I don't think the bushing can cause the vibration, but I could be wrong).

- The boat is primarily used for slalom, with other stuff being secondary (yea, I know it's self centered, but it's MY boat). I would like to have the flattest wake...everybody else can bite me.

- I sent a message to OJ props, who suggested a 12.5X12 LC XMP 4 blade. Does this mean my boat will run higher RPM's since it has less pitch, or does the 4th blade change everything? Does anybody else have this prop on their...ahem..."vintage" MC, and if so, how does it perform?

Any suggestions or advice would be greatly appreciated.

88 PS190
05-22-2007, 11:16 AM
that is interesting stuff.

I would listen to the guys at OJ, they tend to have good advice.

On my boat the rudder is on the left side when viewed from the rear.

To repower to the opposite direction you either mount an engine that turns the other direction, or mount the trans on the other side of the engine.

The trans I believe you'll have a BW velvet drive like ours does.

TO swap this trans from left to right mainly involves the pump.

The pump is set to provide pressure in the forwards direction by indexing the arrow on the pump to the direction of engine rotation, so if you go from left hand to right hand it simply means that the pump gets reversed. THereby locking the trans into forwards instead of running the planetary reverse gear *very loud and will destroy a trans if used for forwards*

Then you apply the correct prop.

fun right?

EJ OJPROP
05-23-2007, 08:14 AM
I spoke with Cotton from the MC factory this morning and he advised that MC went to LH in 77'. You indeed have a RH rotation propeller. So, I would suggest a 13 X 13 RC 1" FORCE 4-blade for your application.

TRBenj
05-23-2007, 10:27 AM
CC has always run RH props. Before the 1.23 (which reverses the rotation in the transmission) they used reverse rotation motors. This helps counteract the weight of the driver, so its actually a pretty nice setup.

I assume that you have a 1" keyed (not splined) shaft? If so, all the 1:1 CC guys love the Acme 540 (RH 12.5x12 3-blade). I dont know of anyone using a comparable OJ, but if you go that route Id go with the XMP since its CNC'd. I do know that the 3-blade Acme's outperform their 4-blades (both in acceleration and top end).

M-Funf
06-06-2007, 06:33 PM
I spoke with Cotton from the MC factory this morning and he advised that MC went to LH in 77'. You indeed have a RH rotation propeller. So, I would suggest a 13 X 13 RC 1" FORCE 4-blade for your application.

Isn't the RC a S.S. prop? I think I'd like to stay with a "softer" prop. So Do I go with something around a 13X13 XMP as TRBenj suggests...?