More wondering about new diesel boats

[easytimes455]

I noticed that Glacier Bay catamarans now carry a diesel inboard. They put two 380 hp Cummins Merc inboards in their 34 foot cat. Motorboating magazine just did a comparo on it, pitted against another of the same boats but with an outboard powered by twin 250 hp Suzuki outboards.

Just from my observations on diesels, why in the heck didn't they use a less fuel hungry version? I mean it beat the outboards in WOT and cruising speeds, but only barely... because cats are like our boats. They have a design speed and won't go much above that. GB cats are semidisplacement runners. There was some difference in fuel consumption, but using 380 horse engines against 250 horse outboards... what did they expect?

Seems to me a pair 210-260 hp diesels would be the best way to diesel power that boat. Most people who want diesels don't care as much about speed as they do range and fuel economy. Right or wrong?

Am I so far off base on this one? Didn't they shoot themselves in the foot by planting monster HP in that boat? They also put V-drives in it. Seems that would stern load it like an outboard model.
Charles

[Mistress]

I would tend to agree with you.

A friend has a 34' Kevlacat (dispalcement) with twin Yanmar 315's. it'll do 39 knots and does pretty fair on fuel ( I believe about 2 km/g). Mid-mounted engines..awesome layout.

GB does have a good rep for design...so....

[easytimes455]

Shows ya how far behind I am. Before I bought my Shamrock, I was all over Glacier Bay and Kevlacat. Even spoke to Harry "whatshisname" down in Georgia... the manager of the Eastern plant. He invited me down for a sea trial on one of the development boats.

Thirty nine knots???? Holy crap!!! That's a lot faster than the GB boat. About the same as the GB on fuel burn. I like the Cummins in the GB, from what I have read. I guess we'll see how it works in time.
Charles

[FL_Panhandler]

A couple of things catch my eye:

The boat weighs 19,000 lbs. So it is pretty heavy. I don't know if a slow to moderate speed cat would appeal to a buyer over a monohull, so you probably need some power to push it to those higher speeds.

The 380 QSB is the new common rail fuel injection version of the 5.9 liter B series. It weighs about the same as the 250 hp versions you mentioned. Since it is the new fuel delivery system and not higher boost pressure, (like some high powered smaller engines of the past) that gives the power, I suppose there is no real downside to spec-ing this version over the old style ones. Although the 380 hp rating is at 3000 rpm & "recreational." But if you go look at the power curves you will immediately see why they would choose this over an old-style mechanical injection 220B or 270B or even a 370B. http://www.cmdmarine.com/recreationalinboards.html

Run them all at 2000rpm & you get this:
220B: 200hp / 5.9gph
270B: 257hp / 6.4gph
370B: 260hp / 6.7gph
380QSB: 342hp / 6.6gph :shock:

The V-drive probably has something to do with the space available in the hull, but they might also use it to reduce shaft angle. The more you can push back & not down, the more efficient you are.

[easytimes455]

FL_PH,
Those burn rates are no load speeds, right? The word from Glacier bay is the GPH at 2000 for the duet of Cummins in that boat was 15.4 GPH. To its credit, the boat is moving over 20 mph. The Suzuki powered model had to push 4000 RPM to top 20. That made its burn rate 19.5 GPH. Hmm, that feels like a punch in the gut.

I don't believe the Glacier Bay cats carry a design speed of more than 42-45 MPH at WOT, regardless the HP. I shopped them pretty heavy prior to buying my Shamrock. The Kevlacats are more of a planing cat, and can support more speed. Seaworthiness is one of GB's advertised selling points, much like Shamrock, but in a two hull configuration.

The main difference I see in the two 34's is the selling price... nearly $100,000 difference between the diesel inboard and the twin outboard models. Geeze!!! How much fuel do you have to save to pay for that?

I feel less treasonous talking about boats in the quarter mil and up price range on this forum. Like I'm gettin' one next season... right. My traction machine has to fit in the stateroom, ya know.

I think I'll keep my 3+ MPG Shamrock.
Charles