Hatt 39

[Kiffsue]

Hi I am looking at a 39' fly-bridge hat was customized by Hatteras to be an open day boat configuration.
She was originally powered with special order 471 Ti Detroits at 315 hp and has since been repowered with 3126 Cats at a said 350 hp.
I think the transmissions were also changed from the factory 2.9:1 to 2.5:1 ratios.
The boat now is a pig, she appears way underpowered and the cats just can get her on the plane.
My question is what would be the best choice for a repower for this boat.
Am I correct in saying that QSM 11 would be too big?
From all accounts this hulls not only needs hp but torque which the cats don't have.
Has anyone run this boat with C series Cummins?
I am also thinking of finding rebuilt 671 Ti 450 hp like what was an option from factory.
Any thoughts and suggestions on this would be greatly appreciated.

[saltshaker]

The 471TI's were not special order they were the base option for that boat. Ridiculously slow for that boat but that's how Hatteras kept the base price down. Most have 671TIBs at 485HP. I think the Cummins C series will be a bit small but not too bad. I wouldn't expect much more than a 22kt-23kt cruise. The QSM11's would be a real nice package in that boat and should give you great speed and economy. I wouldn't put 671's in there unless you get them for free and do the work yourself. Hard to justify the expense to end up with those engines. Is the boat worth the cost of re-power?

[Blaine Thorpe]

Before you look at changing engines, you might want to look at what it would cost to rerate the engines. Cat had 385bhp and 420bhp versions of that same engine.

Changing to 385bhp should be pretty easy. 420bhp might need some parts change.

[Blaine Thorpe]

Just did a quick check looking at the IMO Technical file for the 3126. All of the iron is the same for the 350 and 385 HP versions.

To go to 420, it would take piston crowns, turbo, fuel pump, and injectors.

[saltshaker]

Before you look at changing engines, you might want to look at what it would cost to rerate the engines. Cat had 385bhp and 420bhp versions of that same engine.

Changing to 385bhp should be pretty easy. 420bhp might need some parts change.
It still would be under powered. How's yours treating you? What kind of speed are you getting?

[Blaine Thorpe]

It still would be under powered. How's yours treating you? What kind of speed are you getting?

As a whole, the QSM11s are running great. Starboard has an exhaust leak I need to address.

We manage 26-27 knots with full fuel and water, a little better on the return trip.

We cruise 20 knots at 1950. I think there is still some room for improvement on the props. I'll pull them this winter and have them redone. We hit something on the Illinois river coming home and now have a vibration, so they have to come off anyway.

[Kiffsue]

Thank you guys for all the feedback.
Yes I agree a Detroit repower would not be a wise move.
I would love QSM11 we have a pair of 550 hp in one of our other boats and they are sweet.
Someone said they may not fit in the 39' I’ll have to go do some measuring, I must say the 3126 fit
very easily with room to spare.
I think this boat will need at least the 420 hp Cats and to go through all the conversion to get these engines up to that again won’t be worth it.
I really like this boat but need to crunch numbers before making an offer.

[jim rosenthal]

You might look on Boatdiesel.com. There were a pair of unused Lugger L6140As rated at 600 hp each- new engines, unused- I know ADA doesn't make these anymore, but they were great engines and they still support them etc. Depending on the price, these might be a reasonable choice to put in that boat.

[nor'easter]

The qsms would be tight in length, but if you move them back they will likely fit. Had a 39 sx for 5 years and worked up a repower. I had 565 hp 692 and it was a 30 know boat with no tower. She liked the deep gears and big wheels. I would go with the 550 or 600 qsc. It would have taken a ton out of the boat with the 92s and been plenty of speed with better economy and super access.