Prop & Gear Box Ratio Recommendations

Longest running airboat discussion on the internet.
Post Reply
PistolPete
Southern Airboat Member
Posts: 31
Joined: Tue Oct 02, 2018 7:24 pm

Prop & Gear Box Ratio Recommendations

Post by PistolPete »

My Son is putting a 14x 8 Alumitec boat together using a Gen 5 6.2l l86 Direct engine 420 hp 460 tq. stock. He wants to be able to run dry ground without any chance of getting stuck, would also like it to run top end about 60 -65 mph. What we were thinking after talking to water walker was 80" 3 blade falcon or Maximus 2.55 OX Box.
Attachments
fullsizeoutput_3ea.jpeg

CarMotorBarge
Site Supporter - I
Site Supporter - I
Posts: 960
Joined: Thu Jul 14, 2011 8:32 pm
Location: Lake Harney Woods

Re: Prop & Gear Box Ratio Recommendations

Post by CarMotorBarge »

Ignore the torque curve on that dyno sheet. It tells you nothing useful when selecting gear ratio and prop. It just confuses people. The HSP curve tells you everything you need to know. I would run WOT at 5400 to 5600 RPM given that dyno sheet. Just have to experiment and find the setting you like.

Do you plan to do any performance upgrades in the future to the engine? What are you using for headers?

If you are planning performance upgrades that will cause the max HSP to occur at a higher RPM, you might want to consider a 2.68.

The Maximus blades are hard to beat when it comes to push on the hill. You should also be able to do 60 to 65 if the boat runs free enough.
14x7.5 Al David hull with 14 inch transom
419 CI Horsepower Barn LS3 with 2.88 Ox Box swinging 4 blade 83.5" R
GTO Rigging and B&S Tilt Trailer

SWAMPHUNTER45
Site Supporter - III
Site Supporter - III
Posts: 3036
Joined: Thu Nov 21, 2013 11:38 am
Location: Naturecoast, Florida

Re: Prop & Gear Box Ratio Recommendations

Post by SWAMPHUNTER45 »

If that is a take out or crate engine what are you planning to do with the ECM ?

PistolPete
Southern Airboat Member
Posts: 31
Joined: Tue Oct 02, 2018 7:24 pm

Re: Prop & Gear Box Ratio Recommendations

Post by PistolPete »

Take out 26k have it programmed for stand alone and tuned

SWAMPHUNTER45
Site Supporter - III
Site Supporter - III
Posts: 3036
Joined: Thu Nov 21, 2013 11:38 am
Location: Naturecoast, Florida

Re: Prop & Gear Box Ratio Recommendations

Post by SWAMPHUNTER45 »

That tune is important for sure.
Post pics as you build her

PistolPete
Southern Airboat Member
Posts: 31
Joined: Tue Oct 02, 2018 7:24 pm

Re: Prop & Gear Box Ratio Recommendations

Post by PistolPete »

Ok this is what we are starting with a never used 2008 14 x 8 Alumitec boat. Got the motor Friday started ordering the parts we will need. we are going to make some changes to seating height.
Attachments
fullsizeoutput_3fd.jpeg
fullsizeoutput_3fc.jpeg
fullsizeoutput_3fb.jpeg
IMG_6382.JPG

SWAMPHUNTER45
Site Supporter - III
Site Supporter - III
Posts: 3036
Joined: Thu Nov 21, 2013 11:38 am
Location: Naturecoast, Florida

Re: Prop & Gear Box Ratio Recommendations

Post by SWAMPHUNTER45 »

A new boat that sat unused for 10 years, that's a barn find!

PistolPete
Southern Airboat Member
Posts: 31
Joined: Tue Oct 02, 2018 7:24 pm

Re: Prop & Gear Box Ratio Recommendations

Post by PistolPete »

I had some other projects come up that I had to do. I am getting closer to the finish line here are some pics. It was a real pain in the ass getting the gmlan protocol to run gauges on Garmin. Right now I am waiting on wire harness to come back from second modification and new wider console and some other minor stuff.
Attachments
aYN7UhILTHKhmCWEWv58ZQ.jpg
YrsebMwgS0uRV72n30pbLA.jpg
EN%knmSXQFqDEcfPf8i6cw.jpg

PistolPete
Southern Airboat Member
Posts: 31
Joined: Tue Oct 02, 2018 7:24 pm

Re: Prop & Gear Box Ratio Recommendations

Post by PistolPete »

more pic Emron semi gloss black with army green webbing then sprayed some items army green with black webbing
Attachments
K44p8oQaTMeIh0KZNCdQng.jpg
3O967+ROS9KwdXQjLPi6Mw.jpg
qmW1+rkoSzCaoUXMfGCpuA.jpg

User avatar
Watterbug
Southern Airboat Member
Posts: 46
Joined: Fri Jun 21, 2019 8:25 am
Location: the big open

Re: Prop & Gear Box Ratio Recommendations

Post by Watterbug »

Dang that looks "Fine"
When you going to get it wet???
Put up a Youtube...
:salute: :salute: :salute: :salute:

PistolPete
Southern Airboat Member
Posts: 31
Joined: Tue Oct 02, 2018 7:24 pm

Re: Prop & Gear Box Ratio Recommendations

Post by PistolPete »

Hoping to be finished in two weeks waiting on some parts. Engine should be bad ass stock with tune its 460hp we put in cam and tricked out heads it’s should be between 590 and 610 hp.

Aeon
Southern Airboat Member
Posts: 156
Joined: Mon Jan 24, 2011 11:11 pm
Location: Orange county-- the wrong one. I'm in California

Re: Prop & Gear Box Ratio Recommendations

Post by Aeon »

If you really have that much power, a 3 blade 82" jx will spin nice. Don't forget a colder thermostat 160deg. Hope you changed out the pistons out.
17x8 Circle H powered by a TurnKey LS3, 2.55 ox box and 82" 3 blade JX

FISHSTICKER
Southern Airboat Member
Posts: 395
Joined: Wed Aug 31, 2016 11:22 am
Location: French Settlement Louisiana

Re: Prop & Gear Box Ratio Recommendations

Post by FISHSTICKER »

Fine boat for sure. PistolPete. I sent you a PM. If you have a few minutes I'd like to ask you a few questions.

Thanks
Eddie.

Post Reply

Return to “Airboat Talk”