Dave,
The R/R camshafts used in the marine applications are unlike the standard cam core in a number of respects. The use of a gear to gear setup (without an idler gear which changes the D.O.R. of the final gear) in a RR engine, the crankshaft is turning CCW (reverse) and the camshaft turns CW, or standard rotation. The cam core used for this type of application is designated a standard rotation/reverse fire core, meaning that while the cam is turning standard, the fire is reversed which alters the lobe orientation on the core. The face of the cam (front journal) is machined in a different configuration to accept the upper gear drive. (See photo)

These cores are unique and cannot be adapted from any existing core. After a number of requests for these cores we contracted with one of our vendors last year to produce a short run of roller cores. The process consists of the following steps:

• A bar/spool of aircraft certified, vacuum degassed, 8620 billet>

• Rough in spool on lathe

• Copper plate spool

• Hob gear

• Cut copper

• Rough mill lobes

• Carburize heat treat cores

• Straighten core 2x

• Grind main journals

• Grind lobes
Bob

clockwise (from the flywheel end) is a counter rotation motor. Standard rotation motor is left hand. I think you meant to say

When is velvet drive going to make a tranny that reverses rotation? A standard 71c or 72c that reverses would be so nice..

The merc 383 4v makes 429 lb torque @ 3800 rpm, you can get them for under 8K. Plug & Play.

key right there is 3800 RPM.... glad Bob chined in...he can do a reverse rotation cam for you...I went thru all this a few years ago..wise I would have bought to of the high torque 502's GM makes, and redid myself to marine engines and had Bob do a reverse cam for one...and yes if they did a 72c reverse would be great !!!!

502HT crate engine =512FT lbs at 2800RPM.

I know nothing about cruisers, but curious.....How hard would it be to adapt to a twin disc transmission? To reverse the rotation of prop, but be able to run two standard rotation engines?

The reference to CW and CCW, in the post, was intended to address the DOR of the crankshaft and camshaft at the drive interface, or gear stack (engine front) to illustrate the cam and crank rotate in opposite directions as compared to a chain/sprocket drive where the cam and crank rotate in the same direction.

When referencing the DOR of the crankshaft during operation, standard rotation or reverse rotation are terms which remain accurate from both the front and rear of engine point of reference. Hope that clarifies the post.
Bob

You can spin them either way by just flipping the pump over but output shaft spin is always determined buy the direction the input shaft is spinning.

wrong !!! you can on a hurth, not 71 or 72, the reverse clutch back is not the same as forward one...I went thru all this when I repowered my gibson...