Mercruiser TR - hp and torque limits
 

I'm trying to find the torque/hp limits for my Mercruiser TR drive. I'm repowering a boat that has it and it looks like it is in great shape (sat for 20 years in the desert). It also has a Borg Warner 72C 1:1 in good shape as well.

This is a diesel powered boat. Old engine was a Mitsubishi 200hp @ 3100rpms. New engine I'd like to make work without spending too much money (I already have the engine) is a 315hp 6BTA Cummins. I'm afraid the torque (700 ft-lbs) will tear up the drive and Borg Warner and plan to pitch down a bit on the prop to keep hp to 250 at WOT. Does anyone know what the limits are for the TR drive and Borg Warner 72C 1:1? An old timer in the boat yard saw my TR drive and said they were old shcool bullet proof, but want to get another data point. Most of the information posted is about TRS drives - are they the same, just shorter?

Prop selection? I've got a 19x23 pitch now. Are there higher pitch props available (ie: 19x26) that are readily available?

Thanks for your help!

The stock Borg Warner 72 is a great unit but would be beyond its limits with the big Cummins but it can be modified to handle the torque of the Cummins. Contact BAM Marine, (MBAM) here on OSO, He does a great job on the BW upgrades.

As for the Merc TR, it might last a little while but when you put more torque through them than they were designed for, the cases deflect and the gear pattern goes away. The teeth usually pull out at the root. Fortunately, Konrad Marine has a direct replacement for the Merc TR, it's the Konrad 520 drive unit. Thousands sold to the US Navy and many other governments all over the world. As for the TRS, they share the same upper but the lower is much deeper with the ability to handle a 20" dia prop. TRS is limited to 16"

Check out www.konradmarine.com

[email protected]

Thanks for the reply. What are your thoughts about the Bravo 2X? I checked the Konrad website - they looke pretty cool to me. How much for a 520?

Get a hold of Kirk Casey in Bellingham Wa. He has extensive knowlege of the Merc TR Drive.
here is an email address
[email protected] <[email protected]>
and a link to his sight
http://kcmarinetr.com/