Inboard Experts

[dsharp]

I don't profess to be an expert but an automotive engine turns counter-clockwise(left hand prop)You always look at a marine engine from the rear. on the 71 and 72 series borg warners the only box that reverses is the 1.9:1. They made a 2.1 to 1 and 1.9:1 to run pairs that used standard rotation engines. Most counter-rotating conversion change the timing chain for a timing gear. Cam turns same dir- crank rotates opposite direction. Some mercruisers used chains and everything ran counter. The starters are always different. Some people have tried to reverse the rotation in the borg warner but they won't hold up because the reverse clutch pack has fewer plates and discs. Physically it will do it but it will not last long. Most rudders are offset like a couple have noted to simplify shaft removal without dropping the rudder. I think Gary made the point that the most important thing about props is the engine has to be able to turn the rated rpm's at full throttle. Some rough rules of thumb are 1" diameter = 2" pitch. Reducing 1" pitch will pick up about 200-300 rpms. A cup will be about the same as 1/2" of pitch. There are really to many variables to try to compare what someone else is running. You can shift the weight in a planing hull and lose 300 rpm. Like I said these are rough guidelines. The best way is to run the boat with normal fuel load, gear etc and see where your at. You generally don't want to get to far off from square though. No expert-2nd generation boatyard rat.