design of transmissions

[DuaneIsing]

I got into a discussion with some sailors the other night at the USCGAUX meeting and it was obvious that most of us don''t know how the typical sailboat auxiliary transmission works. I tried to research this on the web this morning with no success.

Can anyone out there point to a web-based resource(s) that will show/explain the mechanical design and functional details?

[Denr]

If you ask some specific questions, I could probably answer them. Marine transmissions are basically 2:1 reduction gearboxes with sliding clutches to engage the prop in both hands of rotation as well as no rotation aka. neutral. Most use an ATF as the primary lubricant. The way most of us use our boats, the ATF should be replaced every 100-150 hours.

[Denr]

If you ask some specific questions, I could probably answer them. Marine transmissions are basically 2:1 reduction gearboxes with sliding clutches to engage the prop in both hands of rotation as well as no rotation aka. neutral. Most use an ATF as the primary lubricant. The way most of us use our boats, the ATF should be replaced every 100-150 hours.

[tsenator]

DuaneIsing,

I don''t know of alot of Marine Tranny websites, but here are a few. Some you can even post questions to

This site is where there are Forums/Questions asked:
http://MarineForums.com/

This list spec/info on all sorts of Tranny''s
http://TransmissionMarine.com/

But I think the best thing is to order one of these 3 booksYou will get alot more info:

a)Troubleshooting Marine Diesels by Peter Compton for about $15 on Sale

b) Marine Diesel Engines: Maintenance, Troubleshooting, and Repair by Nigel Calder for about $17 on sale

or "THE BIBLE"...(which is great to keep on board for all systems)
c) Boatowner''s Mechanical & Electrical Manual: How to Maintain, Repair, and Improve Your Boat''s Essential Systems by Nigel Calder about $30 on sale

[DuaneIsing]

Thanks, Denr, and tsenator, for responding. I didn''t ask any specifics because I wanted to glean the answers for myself, but just couldn''t seem to find any worthwhile info after looking at over 50 web sites.

The question was prompted because none of the group I mentioned above (including myself) had ever seen the insides of a marine tranny. One of the guys was claiming that putting your tranny in gear while sailing with the engine off would NOT lock the shaft because the coupling between the engine and prop shaft was all hydraulic.

I started thinking about all the possible methods for getting power to the prop (hydraulics, planetary gears/bands, multi-disc wet cluthes, spur gears, cone clutches, etc.) and realized that I had no idea what design(s) is/are actually used.

As to buying a book, I have been so happy with the info from Calder''s Cruising Handbook, that I will just go buy the mechanical repair book, too.