close to a solution!

[David Dillehay]

The mystery transmissions have finally been identified by some help from this board and the prop solution hinges on one last unknown. Roughly how much does a 1972 Hatteras 38 C weigh?

Regards and thanks in advance,

Dave Dillehay
Aldora Divers Cozumel

[Boatsb]

about 31,000 Lbs. then add the weight of the personal junk known to be hiding in every crack and crevice.

[SKYCHENEY]

Did I miss it? What trans are they? Twin Disc?

[David Dillehay]

Dear Sky,

Thank you so much as you were the one who led me in the right direction. After your comment I went to the twin disc web site, saw nothing that they now offer that looked like it, but sent lots of photos to their distributor in Lousiana who confirmed that they are vintage MG 506 s.

Going further he confirmed that they can only be 1.5 or 1.97 to one ratios. Given how the tachs looked when both had the same oversized propellers on, I have deduced that the port is 1.5 and the starboard is 1.97. That due to the fact that the port engine was lugged down much more than the starboard.

But I have ordered a photo tach to confirm all this and should have it known for sure whenever I can get it here to the Yucatan.

Now I have the decision to make about what to do about it. Maybe I ought to just look for a used MG506 of either ration and prop the boat for that. My guess is that I will prefer a 1.97-1 allowing bigger props. But maybe just having two seperate size props is the simplist. What do you think?


Dave Dillehay
Aldora Divers Cozumel

[Boatsb]

I have the 41C and it is close to the 38. I believe I have the 1.5:1 gears and I spin 23 x 23 props. Check with the other guys on the site who have the same vintage 38's and see what they have. Hatteras did not choose the transmission gear ratio without some research. At the 289 HP and the 23 x23 wheels mine do 16 Kts cruise and 19.5 - 20.5 WOT per GPS averaged both ways depending on the load and sea conditions.

[spartonboat1]

Hatt 43'MY's had the TD MG506 units...per TD, just about last forever.

Per the TD manual, SM-146, shallow case, Marine Gear, the following ratios were available: 1.47, 1.93, 2.42, and 2.91, all :1. My Hatt owner's manual specifies that 1.97:1 (typo? assume meant 1.93:1, as all documentation was hand-typed in 1972. Ask me about an IBM Selectric...) was fitted with J&T 6-71N, 310hp.

P.s., use the 40wgt straight wgt oil in them. I tried synthetic one summer and they seemed grumpy...used oil and never did that before. No using oil since went back to Texaco Ursa 40.