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**CClassic28** · 05-02-2005, 08:30 PM

Larry,

Those are some impressive stats!! I can't believe the difference between your boat w/260's and mine with 250's.

What props are you running?

Chris

**backman** · 05-03-2005, 05:30 PM

Acme 18 X 26's

I too had a long talk with Bill Weeks at Acme after talking with Mac.

The leading edge is thinner than a Hi Torq, but its not tissue thin as was posted elsewhere. Depending on what you hit and how you hit it the Acme's can be repaired just the same as any other prop. According to Bill they have more thickness in the root and inside half of the blade than other props.

What do the 4BT50's use for gears and props and what is WOT? I believe you max. out at 2800 RPM and use a 1.5 to 1 reduction gear?

I believe the math of the D4-260's is good because they turn 3500 WOT and use 2:1 gear reduction. Speed is effectively driven by RPM's and pitch and pitch is related to prop diameter. We're all limited by the geometry of engine and shaft angle and size of the hull to an 18" diameter. Most prop books say you lose efficiency in a prop when pitch:diameter gets greater than 1.5:1. Ergo 26 or 27" is as much pitch as your going to get out of a 18" prop.

The beauty of the repower was that I got new struts, shaft and logs which enabled the extra inch of diameter which led to more pitch.

I went from 230 to 260 HP, but more importantly went from 17 X 23 to 18 X 26.

**CClassic28** · 05-03-2005, 08:30 PM

Larry'

The 4bta250's are rated @ 3000 RPM, and gears are 1.56:1. When I was speaking with Bill, He thought that 18" wheels where going to be too tight (less than 10% clearance) and steered me back to 17" (17x20)

I am very pleased with the improved performance and running attitude of the boat with the new props but wouldn't mind being able to run comfortably @ 28 without pushing the motors too hard. Well, maybe next time!!

I am turning up just shy of 3100 so if I wanted too I am sure a little more cup this off season would give me a little more speed @ higher RPM's. So far I am very satisfied.

How did you manage 18" wheels? Increased shaft angle slightly?

Regards,

Chris

P.S. I see from the pics that Eric posted your boat raises some giants!! Way to go!!

**backman** · 05-06-2005, 10:14 PM

More impressive in sloppy conditions

I went for a quick cruise this afternoon in the beginnings of a 2 day noreaster.

The weather tower in the sound said 21-24 knots; I'd reckon it at 17-20 at sea level and the usual nasty wind blown 2-3' slop/chop. The stuff the center console guys call 6'!

My KAMD42's were inadaquate in these conditions and had to push hard/say 82% throttle with lots of governor surging to move the boat at 21-22 knots. Hit a wave wrong and they would drop off 200 RPM's and the boat would slide off plane. The engines would suck 20 GPH to do this, much of it wasted.

I banged into wind and tide at 2850 RPM/23-24 knots, no surge, no change in engine RPM, 9.3 GPH per engine for the couple miles I ran. Coming back, wind and tide at my back I was doing 25 knots at 2700 RPM, steady as a rock on the throttle, ~ 7.8 GPH per engine; for laughs I pushed up to 2850 adn found myself going 27 knots.

I'm more impressed by the slop performance today than by the raw flat calm performance on Monday as much of my boating is in Vineyard Sound which is usually 15-20 miles of wind against tide slop. Real bass; the 15-20 pounders are going to show up at some of my spots in a week and I'm pumped to make a run down there at these speeds after years of slogging along at 21-22 knots.

**Split Decision** · 05-06-2005, 10:54 PM

These electronic diesels really work great. Up and down the waves they never change RPM. Even when I was coming home in the 4-6' seas and the boat came out of the water a few times the RPM never changed more than 50 RPM. We will see in the long run.

**backman** · 05-13-2005, 10:18 PM

Its a 33.5 knot boat baby!

Flat calm today; ~190 gallons of fuel aboard.

Just like Mac said when he convinced me to go w/ the D4's as opposed to the 300's. - The boat hits 33.5 -> 34 consistently w/. no tide and wind and turns 3610, or 110 RPM's above WOT. I think if I had more balls I could have gotten it over 34 knots but I was only doing WOT for 30 seconds max.

It will hit 28-something at what I consider a nice cruising RPM of 3150/90% thottle.

The best in terms of usability is how well the engines survive tidal flow. We have a couple points and throats here that have a 2-3 knot tide when its ripping and which w. my old 42's were a 21 knot struggle. The D4's will make an easy 25-26 knots against this tide at 3000 RPM and change.

That's more a reality for me than WOT and opens up new approaches to inshore fishing for me. I was previously trying to avoid 15-20 mile inshore runs against the tide because it worked the old engines too hard and took too long.

**rob** · 10-12-2005, 03:32 AM

D4 260 performance

hi guys, just put a deposit on a 28 with the D4 260 package and am working on trying to get it to hawaii where I live. Read beckmans specs on performance and was wondering if that GPH number was for the pair or 1 engine. I chose the volvo package over the yanmars related to my experience with a 200 duoprop I have here for 5 years. The one problem I had was that surge/loss of power going down sea. Got great mileage out of her, would average 25 gallons per day. Here we typically only run 10-15 miles in 3-6 foot trade blown seas and troll all day. I was hoping the common rail engines would be fuel efficient, even more so than the yanmars. Those speeds sound awesome as well. Have not personally seen the boat yey but would assume with the 4 cylinders instead of 6 there would be more than ample room in the engine box????? How is maintenance on these engines, performed all on my volvo and am planning to do it again. If anyone has any ideas on getting one of these to hawaii let me know. THanks to laukia for giving me a tour in sandiego this summer, almost talked myself into a 32 cat but changed my mind after hearing all the positives of this boat from its owners and web site. Mahalo and will be a regular soon on this site. Rob C

**backman** · 10-12-2005, 08:11 AM

Contact me for more details

[email protected]
and I'd be glad to discuss.

After 380 hr's and 1 season 90% complete I continue to be very impressed by the D4's.

Those #'s BTW are for a dual engine package. After 20 odd offshore trips this year I've settled on a 25-26 knot run out @ ~20GPH/3070 RPM's. My boat is a scow when I leave the dock; full fuel; 4 guys; 200+# of ice and sometimes an additional 30 gallons in a bladder.

Coming back with perhaps 1/4 to 1/2 tank I get 27-28 knots @20-21 GPH/3150 RPM.

The engines sip fuel trolling - I average ~3-4 GPH at 1380 RPM's/7-8 knots trolling speed. Drop down to 1250 RPM/6 knots and its 2-3 GPH.

10-15 miles each way and troll all day is perhaps 15 gallons running and 16-25 gallons trolling depending on how fast you troll so the fuel burn is close.

he D4's are a lot shorter than the Yanmars and there is a ton of space forward of the engine for maintenance. The engines are designed with consideration towards maintenance with all filters on one side; water pump easy to get at; belt accessible up front. YOu should order the oil extraction pump and have it plumbed both for engine and gear oil. Transmission access is the worst part of the setup and plumbing in extraction capability from the start will save you time on maintenance.

After 380 hr's I have had no major problems; 2 minor leaks to be fixed under warranty this winter - on one engine the o-ring between the dipstick housing and oil pan is leaking a very slow stain; not measurable, but visible in the bilge. the other engine has perhaps 5 drips of oil/trip coming out of one of the valve covers.

If you have not seent hem the D4's come with an aluminum heat shield over the top of the engine - the valve covers/ fuel lines, manifolds, etc. are neither visible or accessible without removing this.

**Laukia** · 10-12-2005, 12:06 PM

First Carolina Classic 28 in Hawaii......

Congratulations, Rob! I'm thinking your going to be real pleased with your decision. Keep us all posted on the progress. I'm still entertaining the idea of getting Laukia over to the Big Island someday. I'm going over in December to take a look around. Good luck and stay in touch.

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D4-260 performance numbers

D4-260 performance numbers

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