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New Cummins/Mercruiser Project

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Old 09-29-2008, 11:22 PM
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I think the boat will do what you want do. I'd probably crank them to 500hp just because I want to be faster than the next guy but you don't have to be.

There is a Super Hero 40 on here with 300 Cummins B's in her. I think they said she ran about 50-53 mph???

The 40 SH boats with a full 380 hp B in them and full of ballast (total weight 14,000lbs +or-) ran at 60 -62 mph with a slight reduction gear just above 1:1 don't recall but are in my notes some where.

That's why I say 70's is reality for 500 hp and 440hp is probably.

I think you won't the Hp to swing the 19's, there a BIG blade hard to get on plane with a big wheel but you have 1.30 gears so maybe??? Hey, worse case you take a little dia off them and go from there.

Joe Gere
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Old 09-29-2008, 11:30 PM
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JCPerf,

I know your an engine builder so what point are you trying to make with "People look for the HP#s to go fast.Torque is very important to turning a big pitch prop"?

That torque allows for a good cruise speed but Hp gets you there first?

Joe Gere
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Old 09-29-2008, 11:44 PM
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Quote:
Originally Posted by HabanaJoe View Post
JCPerf,

I know your an engine builder so what point are you trying to make with "People look for the HP#s to go fast.Torque is very important to turning a big pitch prop"?

That torque allows for a good cruise speed but Hp gets you there first?

Joe Gere
Torque lets you turn a big pitch wheel to get"over the hump" so to speak.It definately gives you a great cruise.If you have 500HP with 500 FT. LBS of torque and you have a boat with 500HP and 1000 FT. LBS or torque the one with the more torque will turn a prop with probably 4 inches of pitch more.Thats where your cruise and gas mileage will really shine
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Old 09-30-2008, 12:03 AM
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The 19 inchers are really big ,I have to grind some fiberglass away from the pulsdrive unit to have some clearence .

There is some suction built into the pulsedrive unit ,there is a hole that is been drilled in the shaft support (can this called a strut ? )a couple of inches above the shaft bearings in the fiberglass structure with a hose that runs through the inside of the box to the top with a thru hull ,plus the pulsedrive unit is trimmable

The exhaust gas from both engines can go out throught the pulsdrive unit ,and exits to the bottem of the box through +- 15 two inch holes.

I will first try and see how the engines will do when in stock form




Can,t wait to try the boat out.
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Old 09-30-2008, 07:52 AM
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JCPerf,

How does anyone make an engine have 500hp with 500'lbs or 500hp with 1000'lbs.

If the Hp of both engines are equal the only way to have difference amonts of torque is to have them develope the Hp at different rpm's.

I know you gave an exaggerated example but what you describe is the basic difference bewteen gas and diesel engines.
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Old 09-30-2008, 03:14 PM
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My Round Britain 2008 raceboats performance figures:
36 ft Ocke Mannerfelt-hull
2xVolvoPenta D6-435(3700rpm) and DPR-drives
GR-9 propellers modified w 31" pitch
12000 lbs dry
75 mph with 1100 liters of fuel at 3700 rpm-could use larger propellers
On the 210 nm stage from Inverness to Edinburgh I backed
of once from WOT.
We drove the boat from Sweden to Portsmouth and Round Britain. 2500 nm together.
No problems whatsoever. The engines used 2 liters of oil during the 2500nm.

www.teamvilda.se
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Old 09-30-2008, 07:03 PM
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Originally Posted by 7075T6 View Post
My Round Britain 2008 raceboats performance figures:
36 ft Ocke Mannerfelt-hull
2xVolvoPenta D6-435(3700rpm) and DPR-drives
GR-9 propellers modified w 31" pitch
12000 lbs dry
75 mph with 1100 liters of fuel at 3700 rpm-could use larger propellers
On the 210 nm stage from Inverness to Edinburgh I backed
of once from WOT.
We drove the boat from Sweden to Portsmouth and Round Britain. 2500 nm together.
No problems whatsoever. The engines used 2 liters of oil during the 2500nm.

www.teamvilda.se
WOW...
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Old 10-01-2008, 08:25 AM
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Originally Posted by stirling View Post

Joe , I bought 2 ZF 110 TS transmissions with 1,30 in 1 th gear and 1:1 in 2 th gear ,I,m using Yanmar 440 ,s with a pulsedrive unit ,do you think I have made the right choiche in gearing ? Now I can have 3450 rpm propshaft speed in 2 th gear ,oh the boat is a Baja 40 outlaw poker run light weight.
I do not know any weight ,but guess about 10000-11000 lbs ready to go.

According Supertermoli ,he had those yanmars turned up in fuel to make 500+ hp and used them for thousand+hours or so ,with no problems at all.
,I,m going to install pyro,s to keep an eye on things.

I,m still busy with trying to put this whole puzzle together,and hope to be ready next year june .

The props i have bought to start with are Rolla 19 inch diameter and 26 pitch 4 blades cleavers,they are probably to big in pitch ,but I need to make a baseline to start with .

I don,t no nothing about these setups with diesels /ratio /slip etc , what I do know is that all I have learned about gasser ratio/slip etc is not comparable with diesel setups .

A.J
I have a 43 Black Thunder with @ 650hp, 650tq. It's a little heavier than a 40 Baja but it's an efficient hull. With Bravo 1 26 pitch props at almost the same prop speed that you are projecting, I go 78 mph gps. It seems to me that your props are too big. The diameter is odd. Most sportboats with Arnesons are using something in the area of 17 dia. If the boat hooks up well, 26 pitch will be too much. You'll need more like 600 hp to turn them. I'd try something more like 17 dia. x 22 pitch to start. Maybe 17.5 dia. if you are more concerned with cruise efficiency.
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Old 10-01-2008, 08:44 AM
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It's easy to see what Habana Joe is saying about hp vs. torque. A HP500 running through a 1.5 Bravo 1 puts out 500 hp but torque is multiplied by the gearatio. So it becomes 500hp and about 800 lbs. torque at the propshaft. Now it seems more like a diesel.
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Old 10-01-2008, 09:05 AM
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You guys push me to look up to much old stuff!!!

ParriYacht is dead on the the SH's had 17" & 16.5" dia props with the Arenson's.

I can't find a pitch number but with that 1.30 reduction you have lots of torque to start spinning a prop with. After you shift into direct?????
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