55 foot Custom Repwer HP

[johnrosson]

I am interested in a Custom SF - 55 foot to 62 foot - there is one boat I like that is a mid 1980s, 55 feet, DD 8V92s with 4000 plus hours - 735 HP.
We plan to repower for sure, complete refit in the engine room including engines, gens, pumps, trannys, Delta T, Props, etc...etc...
I really like the QSM 11 engine at 715 HP.
Do not like MAN, MTU, Volvo...just personal pref.
Might consider CAT or Yanmar, but prefer the QSM 11.

Question:
For the boat we have our eye on - 1985 55 Ft Custom SF
Current Detroit 12V92s are rated at 735 HP.
The QSM 11 would be rated at 715 HP.
Is it a bad move to 'not' increase the HP on a 'repower' of a boat this size?
I am not a speed demon, wife and I really like to cruise, do not fish that much/ a little.
But we prefer the Custom Florida and Carolina sport fishing boats...

Thoughts are apprciated.

Many thanks

[Capt. Mark]

Depending on the particular hull and weight, QSM 11 might be slightly underpowered. That being said, we replaced the 8V92's in our 48 Viking with the QSM11 Recon .. going from 735hp to 660hp. But, our cruise speed went up from 22-23kts to 25.5-26.5 kts. In addition our fuel burn went down from 60gph to 44gph @ cruise. Top end was around the same @32kts. We have over 6000hrs on the QSM11 and its been incredibly reliable. Our repair list in those 6000hrs includes an alternator on each engine, replaced injector "O" ring on one engine, replaced fuel pump on one engine due to failure and repalced the other as preventitive maintence. Overall, we couldnt be happier with Cummins. On the other hand, two identical 42' express boats were recently built, one with QSM11 and the other with C12. The C12 was substantially faster, so in a larger boat that may be a factor. Good luck and feel free to ask any additional questions ....

Mark

[Ace1st]

John....welcome to the site. Nice first post. Way to jump right in and get your feet wet. Someone will come along shortly that can answer your question. And if not, send Seapower a PM. I know he'll give you some insight.

[Top Notch]

We just got thru repowering a 53 Hat with the QSM-11. The boat had 12V71TI. The 12s had 650 HP and the QMS-11 have 715 HP. The big difference was the weight of the two types of engines, 12s weight around 6700 lbs and the QSM around 3800 lbs. We endend up droping somewhere around 6000 lbs out of her. The boat runs great , has more pick-up out of the hole and has a cruise speed of 24 knts. with a fuel burn of around 46 hr. And what a engine room now. You can get around the engines without having to crawl around like a snake.

[gottaflylee]

johnrosson, welcome to SFC. I ran a 50' Ricky for 5 years with DD892s and they ran like a top. Had 3000 hours on the rebuild when I got on the boat and over 8000 when I got off with very little work needed still running to this day. Keep the oil, filters changed and the fuel fresh and they should run for a long time, if you don't mind running oil slingers, as you will have to clean up behind them...

[scattered_grass]

johnrosson, welcome to SFC. I ran a 50' Ricky for 5 years with DD892s and they ran like a top. Had 3000 hours on the rebuild when I got on the boat and over 8000 when I got off with very little work needed still running to this day. Keep the oil, filters changed and the fuel fresh and they should run for a long time, if you don't mind running oil slingers, as you will have to clean up behind them...

That was a beautiful boat for sure. Last time I saw her she was in dire need of some TLC though...I heard she got sold for real, real cheap.

[54bullwinkle]

Here are some specs that might help you

Had a 54 Florida Custom with DD 8-92's (just repowered when I bought her) Rated about 760 HP. She cruised right at 28 kts, topped out at 33.

She weighed 46,000 lbs. Convertible with a tower

Considered very fast in 83 when she was built and pretty fast in 95 when I bought her.
Not fast by today's standards.

I would be reluctant to go with less HP. Market wants boats that cruise 30+, so consider resale value in your decision.

PS....... Your engine room dimensions make limit your choices.

[seapower]

Cummin's. But my answer could not be any better stated than what "Capt Mark" already stated. Look at the weight lose, decrease in fuel burn, never mind the trouble free service they've got from them. These engine's speak for themselve's, no kidding. One thing that hardly ever get's mentioned is torque! Look at the torque curve's on these engine's, that's low end torque. It's the difference between getting smacked between the eye's by the fist of an 8 year old, as compared to an 18 year old. If the bulk of your power come's from the last couple hundred turn's, in my opinion, you've got nothing. Look at the track record of all the engine's you've listed, I'd be willing to bet one will stand above the rest. My money come's hard, but if was mine to spend, the choice is obvious. JMO, Frank

[Capt.Troy Crane]

Dido to what Frank said......there is no comparison to the torque between the two engines in questions. forget the horse power, it is not even a factor when comparing those two engines. You will be more than happy with the performance of the Qsm's.

Good luck,
Troy

[hubris 1]

I have to agree with frank.......to a point. I think a 1985 boat needs a different thought pattern. It was never meant to go 32 kts. Dont try to make it do it. I think HP needs to match the hull and boat, not just say.....HEY, Everyone today is doing 38 kts, I need to do it too. You dont increase a boats value that way when its a 1985. Think smart, put a package that matches the hull, its 1985 inception, and your requirements. Nothing I hate to see more, A guy buys a 20 year old boat and right away thinks.........This thing will fly with double the engine HP.
A guy like me, cant dance with a girl thats only 4'6" tall. Its the same thing. So put on a nice CD, twirl your wife around the room and ask her........Honey, am I going to fast? When she says, NO............thats it! Frank, correct me where you will.