repower with 6v92

bestfish

Lieutenant Commander
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Feb 27, 2012
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Cape Cod
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36' Harris Cuttyhunk
As some of you recall, I have a ongoing 36 Harris Cuttyhunk project. Long story short I'm going to repower with a 6v92ta 550 hp. Reason for the motor choice is that its already paid for and sitting on the shop floor. It has a 1.5:1 Allison bolted up. So...with the old tired 6cta running a 2:1 I could get [email protected] . If I keep the same wheel with the 1.5 (and more hp) I should be able to get all of 20kts at a cruise rpm of 2000? I figure the detroit will add about 1000 lbs. Thoughts?
 

djmarchand

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Jul 24, 2012
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Litchfield, CT / Punta Gorda, Fl
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Atlas Pompano 23 outboard
Assuming your 6cta was 450 hp I plugged in its data into boatdiesel's calculator and adjusted the displacment until I got 22 kts at 2,600 rpm. Then I upped the displacement by 1,000 lbs, changed the hp to 550 at 2.400 and the ratio to 1.5. The calculator showed that the boat topped out at 23.6 kts and cruised at 18.4 kts at 2,000 rpm.

You will also have to repitch your prop.

David
 

petrel

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NC
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56' DMR, 31' BHM
Who runs a 550 hp 692 at 2000? I wouldn't do it for long.
 

Blitzen

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Sumday Isle, RI
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Flowers Boat Works 46 hull #1, Flowers Boat Works 36 hull #1, Wayne Beal 28 Hull #1, Repco 30 1968,
The pumped up 6-92 is like holding a hand grenade with the pin pulled out.
It is only a mater of time.
 

petrel

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56' DMR, 31' BHM
Will your 507 fit the 692? If so, maybe keep it and use instead of the Allison. Maybe you could go w/ smaller injectors there and if the detuned 692 will turn a bit more wheel than the C series, you could end up w/ a workable repower and cruise it around 1800. 'Course it won't sound the same when you back up...
 

bestfish

Lieutenant Commander
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Feb 27, 2012
Posts
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Location
Cape Cod
Boat Make
36' Harris Cuttyhunk
I used that calculator on boatdiesel too. Which hull design did you use? My thoughts were based on shaft speed. If I had a shaft speed of 1300 rpms=22kts. With current prop (which i thought was a little to much for the cummins) Either way the motor will work just fine. Might be a little noisy and messy, but like they say 'cheap is good, free is better" No need to detune, it's much easier to pull the throttle back a couple hundred. Not that I could afford that kind of fuel burn anyway! Thanks for the input
 

Alison Tuna

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Feb 28, 2012
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Hampstead, North Carolina
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Privateer
Yeah...2000 it too much....1500 or norm for our 892s. They show not heat etc. sometimes 1800 to blow them out but at 2000 all the time you'll blow it up in a month
 

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