SBC 350 300hp Gearbox Info

Automotive powered airboat discussion.
Phantom5
Southern Airboat Member
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Joined: Thu Sep 28, 2017 9:19 am

SBC 350 300hp Gearbox Info

Postby Phantom5 » Mon Feb 11, 2019 7:02 am

I have a 15x7.6 Panther with SBC 350 w/300hp. I have 3 different prop setups: 2/ 72" Whispertip, thin, 3 blade with 72" whispertip and a 4 blade hub with 72" Whispertip I want to run a Roatator. What gear ratio would you recommend for the 3 different prop/hub setups :old_glory:

One Eyed Gator
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Location: Ocala,Fl

Re: SBC 350 300hp Gearbox Info

Postby One Eyed Gator » Mon Feb 11, 2019 8:42 am

What rotation are the props you have? DD and Belt-drive are left-hand and gear-box is right-hand rotation.

Also 72" is a fairly short prop for a gear-box

I ran a 81.5 2 bld R on a 5.3 (maybe 285hp) with a 2:1. Then changed gearboxes, went to a 2.68 with a 79" 3 bld R. Also set-up a buddy's l33 5.3 (maybe 320 hp) with a 2.55 and a 80" 3 blade Maximus.

Both boat are 14' x7-6" and his hull is a good bit heavier but both run well.

Phantom5
Southern Airboat Member
Posts: 17
Joined: Thu Sep 28, 2017 9:19 am

Re: SBC 350 300hp Gearbox Info

Postby Phantom5 » Mon Feb 11, 2019 2:52 pm

Thanks one eyed gator.... just trying to get some ideas on how to finish this rig out. Going the DD route first because the engine stand is not interchangeable and if I did go gearbox I would also go for side by side seating change also.

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Rick McC.
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Joined: Wed Jan 11, 2017 10:14 pm
Location: Weeki Wachee, Fl

Re: SBC 350 300hp Gearbox Info

Postby Rick McC. » Wed Feb 13, 2019 9:17 pm

Phantom5 wrote:Thanks one eyed gator.... just trying to get some ideas on how to finish this rig out. Going the DD route first because the engine stand is not interchangeable and if I did go gearbox I would also go for side by side seating change also.


Did you note his info about prop rotation direction?
"Sights are for the unenlightened."
Rick
http://guntipsandtalk.com

Phantom5
Southern Airboat Member
Posts: 17
Joined: Thu Sep 28, 2017 9:19 am

Re: SBC 350 300hp Gearbox Info

Postby Phantom5 » Fri Feb 15, 2019 12:16 pm

If I have a 15x7 with 22" sides 1980 Panther, 1979 SBC 350 270-300hp and want to go to a Rotator Gearbox:

Motor was built with RV cam and max RPM's under load was 6000. It was built for a dirt track car and never raced.

2.3-1 turns of the crank shaft turns 2.3 rotations to 1 of the prop So to drop the RPMs down to 3000 max working with a 2 blade prop would you run with the 2.3-1 or go to a 2.68-1


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