Mystery Trans ID'd, new problem.

[David Dillehay]

Now, I know they are Twin Disc MG 506's thanks to a lot of help here, but one seems to run at 1.5 - 1, and the other at 2-1. The port trans, what we think is 1.5 to one, is spinning the prop CCW looking from the stern. The starboard side is spinning CW and that follows the arrows which are the only markings of any kind on any thing. My guesss is this boat is set up to run in forward gear on the starboard side, and reverse on the port side.

I have been looking for a used trans to make both 2-1 but have just been informed that it may be...some transmissions have different ratios between forward and reverse. IF that is the case, then buying a 2-1 tranny in the States, and shipping it down here, paying shipping and duties ( not to mention the bribes) and finding out it is the same thing I have is not what I would think of as a good idea.

SO! Does anyone know if a Twin Disc 506 has a different ratio between forward and reverse gears?

Thanks in advance,

Dave Dillehay
Aldora Divers Cozumel

[yachtsmanbill]

Dave, I think the 506 is 100% duty cycle in either direction. Your props are doing the right thing. The advantage to the TDs is that you can have 2 engines that are standard rotation and reverse the one prop as it should be. In effect, that trans is running in reverse while turning the prop foeward. Its just a little confusing.
My gas boat with 454 mercs and velvet drives both turn outboard. The velvet drives are the same thing. 100% in either direction. On those you turn the pump housing on the input end 90 degrees to reverse them. My DDs with Allisons both turn inboard with the props both turning outboard. The Allisons have a Left and a Right.
As long as the engine rotation is correct on your boat with the TDs, you can pick the ratio you want (1.5 or 2:1) and replace either gear with the correct ratio.
Look up Luis on the Nina at Caleta harbor. He should have a local contact for a gear for you. ws