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5.3 on a 15x7 set up help


Hi everybody, Im new to airboats and need some direction setting up a 2004 5.3
I’ve ran a lot of other boats up here,
But no airboats. I can’t wait!
I purchased a older 15x7’ 30” deep aluminum boat with a smooth running mild 350 Direct Drive 72” whirlwind 2 blade. Soon to install 3/8 poly.
I’m selling the prop and 350 motor.

I purchased a low hour complete 5.3 with Dbw gas pedal, harness ect.
This should get me a lot more power, reliability, and a little weight savings over the 350.
I want to learn how to drive it pretty good before getting into more HP. Eventually I will build a 6.0 or a BBC.

Looking to build a fairly capable hunting fishing boat.
I want to use the 5.3 factory stuff as much as I can to keep the cost down and keep it reliable.
Any recommendations for the harness work and tune?
Any other parts to consider?

I have all the parts below except the
prop, cam+springs, and Exhaust.
I will be building the engine. I have built engines before.
Not airboat specific engines though.
I gathered these parts from reading here and all over.

Reliable and as quiet as possible is the goal.


78”-80” 3blade ($1700 used stump puller)
prop or similar? No larger.
Quiet Exhaust system?
Texas speed stage 2 low lift cam with springs and seals?

Rotator 2.37 gearbox
Trunion upgrade
Hardened push rods
Ls7 lifters and trays
Flat top pistons and rod bearings
High volume oil pump
Oil pickup tube brace
Billet oil diverter barbell
Thanks for the help!
prop rotation is right hand rotation on gear box that motor with cam headers good tune should be 400 plus hp with gearbox should run real good over that dd 350
CrossAK. If you are still looking for info I would be glad to help out . I put a 6.0 in my boat last year and helped a friend put an6.0 the year prior. Made a huge difference over the 350 that was in previously.
Make sure your clearance are set right for a high volume oil pump. I personally would run a stock pressure and oil pump but polish the bypass and shim the spring.

If you don't have the trunnion upgrade yet look at the brain tooley shaft kit not much more then the trunnion upgrade

I ran a stock 5.3 with 113K miles on it has over 600 hrs between 3 boat and was still running good when I replaced it with a 6.0.

You can get a set of AFR heads for 515.00 ea, a good spring kit and valve job will be 500-600.00 by the time they check the heads and surface them.
Exhaust - check out Innovative accessories out of Okechobee, FL Norman builds the best headers and mufflers with mounting rings. For quiet look up the Summit racing RV mufflers. A gentleman on here Cntry141iq now passed) one of the quietest boat around used those mufflers with a crossover. If you do a search for him you can probably find his build

If it is and 04 find a TBSS style (new style truck intake cathedral port intake) which will do every thing you need should have 40lb injector Glenns performance in tampa has them for 325.00

I personally run a low lift GM ASA road race cam great torque curve and mid range power designed for on and off the gas and you can run LS6 springs (cheap). Biggest thing it is easy on the valve train.

Just my cents
good luck