Engine Stuff

[REBrueckner]

From the May 2010 issue of Yachting, page 84, THE DIESEL DILEMMA:

Cummins QSM 11: before 2002 this engine topped out at 635 HP, but was common at 580 or 535 HP. Totday it's available up to 715 HP. If you have 580 and want 635HP, it's just a software change....If the engine is still under warranty it's around a $10,000 upcharge, but once beyond warranty its about an $500 an engine. Raising a 535HP QSM 11 to either 580HP or 635HP requires a new turbo charger.....a $1750 part.

Going from a Cummins 370B to QSB 380 you'll see about a 5% increase in fuel economy.

A 1981 50 ft Hatteras with 575 HP 8V92 Detroit Diesels repowered with 715 HP QSM11's ...increases prior top speed of 23 knots and cruise at 18kts, burned about 3 gallons per mile...... to 27kt tops and 22 knot cruise....with fuel burn of about 2.2 gal per mile...the inline six cylinder engines lighten the boat by over a ton and open up a cramped engine room.

The 8V92 was originally 575 HP...had a 12V71 heat exchanger and dry turbos...with a new heat exchanger, and wet turbos and other new parts, the engine became 650HP and then 735HP.

More stuff of interest in that article....

 

[captddis]

With my 8v92 TI @650 HP I get .5 miles to the gallon @ 21 kt. Or 2GPM .
I fail to see the savings.

 

[MikeP]

"the inline six cylinder engines lighten the boat by over a ton and open up a cramped engine room."

And to do so costs...?

"With my 8v92 TI @650 HP I get .5 miles to the gallon @ 21 kt. Or 2GPM .
I fail to see the savings"

Me either. I can't see any reason to do such a thing unless the DDs have exploded and there is nothing there left to rebuild.

 

[nor'easter]

You have to put a lot of miles under the keel to recoup the costs. I considered it with my 39 before I sold her, but could never make the numbers work for me. I also knew that we would want to move up to a bigger C, and she wasn't the boat for us forever.
Foir the right long term/high use siytuation, it might be the best thing to do. Also a nice situation to find when looking for a new to you Hatt and someone else took the plunge.

 

[TopHattandTails]

About 2 weeks ago I asked what would needed to he done to get a 53my to cruise at 21 knots. Got a few thoughts as to stringers, props, shafts, motors, etc. Then the magazine hit. Still would like to see how one would make the changes to get 21 knots out of a classic. I have no need for a repower and won't make the changes- but still fun to think about. If I could get a 53 or 56 to cruise in mid 20's and top out at high 20's - it would be a solution to the only problem with these boats (in my opinion).

 

[Genesis]

I looked extensively at putting QSMs in Gigabite. There are a few 45C Series IIs around that have had it done, and it's NOT a small difference in social behavior (noise, etc) and fuel economy - nor speed.

However - it's damn expensive. You do it because you want to, not for reasons of economy. The amount of fuel you would have to burn to make back the difference is never going to happen in recreational use, and might not even in commercial use. When I had mine quoted out I had bids from around $150-200k all-in, including engines, gears, fab and labor. If I remember correctly the engines and gears were around $42-45k each, so about $100k of the price was the actual hardware, the rest the work involved.

Even if you have DESTROYED mains it's cheaper to buy remans - by far - since they're drop-ins (no mount and engine bed work, etc.)