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Your close to that with the 575hp correct? MHO is 7 to 9 liter engines with higher HP are the way to go with our size boats. My original plan was the 540hp 8.3 Cummins for this boat but got too good a deal on the Volvo. My old boat had a 12 liter and the wieght to HP ratio just was not worth it. I'm thinking I'll be close to the speed with this engine as I was with the bigger one because I dropped 1500lbs. If it was in the same boat I would guess I would maybe loose 2 knots. In this boat I have more wind drag and more wieght inside from bunks and stuff but I'm still thinking a 23 knot WOT.
 

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hydroslave hauler 12 inch and bomar box with cutting boards

i'd hate the send these things out to a twin diesel sport fish as i know they are more at home on a downeast boat....hauler head is brand new, was physically installed but never plumbed......paid 1100...offers.....also have a 4 ft, by 2ft by 2ft bomar/xactics box with rod holders and custom filet table on top....$220 or make offer....located wantagh, ny
 

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Hi John,
We topped off the fuel tanks and ran it yesterday before we hauled it out and adjusted the prop. We added 1000# and gained up 15 turns to 2325. Cat still wants 2350 this is quite expensive for 25 turns, and it won't happen again. And who's to say another 500 pounds of gear she's might be there anyway. Cat estimated about an 8 gal burn at 18kts., but almost double that at 25kts.
 

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Discussion Starter · #545 ·
Ken, the fuel numbers are good, at 24 knots I am burning about 21-22 gal/hr. I have seen a 42 Wesmac that swaped out a 800hp Cat for a 1000hp and the samething happend. With the 1000hp he gained 3knots of speed reduced the engine load from 80% to 65% and is burning less fuel.
The boat looks great. You have me thinking I might have to make the trip up and take a ride on the 38 when it hits the water.
 

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You guys are confusing me by mixing facts with speculation. Why is Cat trying to get 50 RPM above the recommended WOT? Also, a C-12 burns about 25gph at 80% (more speculation on my part, but I do run a pair of them) is that what you guys are saying?
 

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asiegel wrote:
You guys are confusing me by mixing facts with speculation. Why is Cat trying to get 50 RPM above the recommended WOT? Also, a C-12 burns about 25gph at 80% (more speculation on my part, but I do run a pair of them) is that what you guys are saying?


The 50 rpm is assuming clean bottom. As the bottom fouls your WOT will decrease approx 50rpm.

So you set your rpm as full fuel, full gear, and prop it to 2350, and when the bottom fouls (naturally) your rpm will be perfectly set.
 

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oneblitzen wrote:
Mike,
They ran the boat yesterday and it only got up to 2310. Only 10 rpms over rated and they want at least 50. But the numbers were 60% load they were running at 24kts and at 80% it was 28kts. Still need to see the fuel burn numbers for efficiency but it is impressive.

Hi John,
I hope to get over and see the boat soon. Meanwhile, these numbers confirm what I always thought that the power to weight ratio plays a big factory in good mileage, at least for these downeast style hulls. Maybe the larger engines have so much torque at slower speeds that it is still very efficient. The 8gph mentioned from the Cat sounds nice @ 18kts.

My question is if the Flowers is a true 38 from the molds or is he adding in the additional 2 feet after the mold?

Steve

This post edited by Seal29 04:27 PM 06/02/2009
 

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Cat wants everything full, water, fuel,and the engine to be turning 2350 at sea trials to allow for gear, people etc that get added later. If they show up and it doesn't turn up they go home and you have to pay for them to come and do another sea trial. She does run pretty well at 80% load but I like it at 60%
 

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Discussion Starter · #551 ·
Hi John,
I hope to get over and see the boat soon. Meanwhile, these numbers confirm what I always thought that the power to weight ratio plays a big factory in good mileage, at least for these downeast style hulls. Maybe the larger engines have so much torque at slower speeds that it is still very efficient. The 8gph mentioned from the Cat sounds nice @ 18kts.

My question is if the Flowers is a true 38 from the molds or is he adding in the additional 2 feet after the mold?

Steve[/quote]

Steve, come over anytime, I would be happy to show you.
Since the two boats are just about the same weight I would really like to get some detailed numbers for rpm, load, speed and fuel, to compare the differences. The C-12 is about 500lbs heavier than the C-9 and it has 130 ponies extra.
 

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Cat did the same thing to me with respect to RPM's. I had the prop retuned 3x before they would sign off on the start up sheet. I am running the same engine (c12) and hp 700 as you in a 38 Ft. Northern Bay. My boat weighed in around 19000 during seatrials. I am probably a few thousand heavier now and slightly slower. I can still turn 2300 WOT.

Thankfully, I did not have to pay for the return trips because they (cat) blew my starter by wiring it wrong so that covered the 2nd trip back and the third was covered because they didn't install my engine heater. Needless to say I did have to pay for the prop tuning. Out of curiousity, who speced out your wheel? What size?

Besides the C-12 in my NB38 I also have a pair in a 44 Henrquies. The figure of 25 gph @ 80% sounds about right. The NB 38 is getting 1.2 / 1.3 MPG I was running 17kts burning 13 GPH the other day. That was with a full boat, plus a dirty bottom. At any speed my NB will not burn more the 1 gallon per mile.

Good luck - looks like a nice boat!
 

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We bought the prop from Donavan, they did the spec. we hauled out yesterday and went to pull the prop off to adjust it, we noticed that a blade was cracked, then another, and another 3 out of 4 had cracks about an inch off the hub, and thank god they made us pull out for 25 turns or we would have never seen them. They tested it today and started looking for a replacement for it.
 

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Cracks? Oh boy, I would look for a new prop manufacturer, who made those?

Also, isn't CAT going to make you put the canvas on the flybridge if they are being such sticklers for WOT RPM?

I think all this load vs RPM paranoia on their part may have to do with the C-12 aftercooler defect. Do the other engine companies get so anal about WOT?
 

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One thing I really don't understand is when the C 12 was a 3196 660 hp you didn't have any of these issues with sea trials, and the 660 had plenty of problems. So I'm thinking it has to either be the change to electronics or the change of it's name. Pictures of cracks!
Cast in China by Mexican workers, to bad we sold all our metal to them to screw up and sell back to us! ZF blamed it on casting to slow.
 

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WOT

It is very important for diesel engines to achieve the maximum rated governed RPMs before the load of the propeller stops the engine from getting to WOT. Should the load of the propeller stop say a 2800 RPM diesel at 2600 RPM. The governor will allow excessive amount of fuel into the engine in an attempt to get to the 2800 RPMs. This over abundance of fuel causes excessive heat and load in the cylinders, which causes early wear.

If they want 2800 RPMs the builder should wheel you at at least 2900 to 2950. Then once fully loaded and after some time the motor will most likely settle in at hopefully 2850 plus or minus 20 RPMs.

In closing you are better off turning a few more PRMs with less load, then less RPMs with more load as your speed will be the same.

Your ZF wheel looks stressed pretty good. Is ZF admitting to a casting failure? Was the propeller ever repitched prior to install? If so how much. Repitching Nibral Propellers can be very tricky. Even an inch can be a push.

Beautiful boat, wheel her right and your C-12 will last a long long time.
 

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She's back in the water late Thursday with a ZF 32x32 #2 and she's right on 2350 rpm but will only get up to a 94% laod. She did loose a little at 80% she went down to 27kts. It still has a great 24-25kt smooth cruise at 60% load.
 
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