Jet Boat Build Suggestions

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Jet Boat Build Suggestions

Post  DieseLife on May 7th 2015, 11:52 pm

19' jet boat that will run an Aluminum impeller, so rpm limit for an aluminum is around 5500 tops. Impeller will be selected based on motors torque curve.

I have the block torn apart at the machine shop. Trying to decide on compression ratio and cam for my setup to get it close to 500hp as possible.
850 dp carb
Ford racing manifold
Currently 2.5" log manifolds, might switch to thru transom headers
D3ve heads intake and exhaust ported per Scotty tech index
Stock sized valves
Needs to run on 89 octane at sea level
Keeping flat tappet cam style
Had .030 taken off block decks

What compression and cam would some of you run? I have my own idea, but want to hear others. Thanks!

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Re: Jet Boat Build Suggestions

Post  supervel45 on May 8th 2015, 4:33 am

I would stay at 9.5/1 compression or a little less just to be conservative. For a off the shelf cam the comp Xtreme marine 278 would be my choice, with the RPM limit you have. It is rated to 5,800rpm. You said everyone's opinion so that's mine. The marine experts should be along shortly with some other suggestions.

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Re: Jet Boat Build Suggestions

Post  supervel45 on May 8th 2015, 4:47 am

http://www.460ford.com/forum/showthread.php?t=213650 Some pretty good advice you got from Jet Boat experts in this thread I'd say.

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Re: Jet Boat Build Suggestions

Post  supervel45 on May 8th 2015, 5:25 am

http://www.460ford.com/forum/showthread.php?t=119213 Did you look at this page? It gives a pretty good idea on what to expect HP wise.

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Re: Jet Boat Build Suggestions

Post  supervel45 on May 8th 2015, 5:37 am

double post


Last edited by supervel45 on May 8th 2015, 8:58 am; edited 1 time in total (Reason for editing : double post)

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Re: Jet Boat Build Suggestions

Post  DieseLife on May 8th 2015, 2:57 pm

Yes i did get good information, however there no such thing as to much information so i like to get as many opinions as i can.

I did check that out but it seems pretty much comp cam only, i was really hoping others would suggest a build cam/compression for my parts going on the motor, in some brands other than comp.

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Re: Jet Boat Build Suggestions

Post  supervel45 on May 8th 2015, 7:15 pm

Going by the other thread it looks like you decided on a - 4.2cc  piston and have the block cut .030" and the heads at 98cc. You want to cut the heads and fine tune the compression for a slight increase. The problem I see is you did not decide on which exhaust you are going to run. I think you need to decide on the exhaust and make your personal decision on the maximum amount of compression you are willing to risk, and don't let the cam be a factor in that, as was pointed out. Then have the cam custom ground to match the combination. I would decide on the impeller last myself.

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Re: Jet Boat Build Suggestions

Post  res0rli9 on May 8th 2015, 8:07 pm

Go here and ask for Paul Kane he's the Boat guy.
http://www.highflowdynamics.com/

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