Cummins repower transmission questions

[matt.schaefer86]

Avid reader, New to posting here. All info appreciated

Repowering a 1989 33 Tiara fly bridge. It currently has 3208T 320hp. Planning to swap to 6BTA 330-370hp. I’m sure I will have a million questions for this forum but I need to start with what transmissions can work.
A friend has the same boat repowered with Cummins and his transmissions are 10deg down angle.
I have found a good set of ZF 80a. Which I believe is a 8 Deg down angle. Is 2 degrees a big deal? Is it a problem to put the motors on a 2 degree angle to make the 8degree trains work? Thanks in advance

Topic

[matt.schaefer86]

There are twin disc in there now. The 3208 sit on a huge angle. I’m pretty sure the twin disc have no down angle. I think the Cummins are supposed to go In as close to flat as possible.

[Luke Nelson]

What GB is in there now? And why not reuse it?

[matt.schaefer86]

Thanks for the replies. I didn’t know the ZF80a were not preferred. Not going to use those now. On the hunt for 220a now. This was very helpful!!

[john]

To me going to all the trouble of repowering and using something that is a deal vs the perfect choice is just bad judgement. I am with Rob on this one.

[glenn111]

At one point, the ZF80A’s would fail over time when run in the “full power-reverse” mode when matched to the 330 PORT engine of Maxum 41′. That is the port engine on a dual engine boat. The flywheel was too light in this configuration allowing plate chatter to heat-up the gear box. No problem with the stb engine, which has the gears running in the forward direction under cruise. Cummins recognized this problem. The 370’s had a heavier fly wheel and didn’t experience this concern, I was told by Cummins. The several I know personally that failed were manufactured in late 1990’s. They may have corrected this later by upgrading to the 370 fly wheel, as they did mine. From my experience, Rob’s comments make a lot of sense.

[Rob Schepis]

A couple degrees nose up is no issue. But a “good set of ZF80’s” needs to be re-considered as that gear does not have a good track record. Would I run away from a used boat purchase because of them, no, not if they checked out good… but I would not install a set as part of a repower. I’d look to go with the proven ZF220A’s and then you’d get your 10 degrees.

[Author]

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