Only problem i see with the hat, is on high boost setups, you really need to mount the hat straight on. Meaning the inlet should face the front of the boat. My buddys setup would make one bank run a bunch leaner than the other bank. Probably not an issue with lower boost, and a spacer between the hat and carb can help that out a bit. I think the hat is the way to go.

Not saying it can't be done but if it was my hard earned money on a forced air motor I would want to get the tune as close as I could on a dyno and then re-tune in the boat using afr and plug readings. Afr's are great but they don't tell you what each individual cylinder is doing. I would also want a hat as opposed to a box not just for tunning but if you had an issue down the road like stuck float or something it would make life alot easier.

The hat is not "legal" on a boat..only the box with a carb, I ran this setup for 2 seasons, had Patrick @ prosystems build me a carb, was spot on out of the box, the box is a royal pain in the a$$ to deal with as you need to remove the top to make any adjustments, also need to remove carb to remove bowls, the issue that I kept having was carb flooding when coming off plane, had to cycle the fuel pump(elec) off for a few seconds to get by with the issue...switched to our own EFI and never looked back...performance is ok with the box though...good luck

what unit do you run and how much boost?

This is something else that I was going to put in my other post aswell. Also running a flame arrestor is '' said '' to smooth out the turbulence, Find out what kinda coin your buddy is looking to get ??


EZ. This is also correct, the hat isn't certified by the coast guard.

Said engine is a forged 355 sbc. Going to run about 10-15 lbs through it. Just trying to get a good idea.


As always thanks for the info. I am running a procharger on my vehicle, but it is EFI, not carbed, so would like to get as much info on a carbed set up as we can. Been doing a bit of reading about it aswell. Thanks

John jr

I run the Vortech blow-through systems with boxes , i used Quick fuel Q-750-ban carbs did not have any problems with the tune up . The AFR gauge would be nice for a reference, but it is tough to watch to be able tune off of , dyno pulls are much more user friendly ,I just added boost pressure and fuel pressure gauges to the boat . The only problem I had was the return line off the fuel regulator was too small and made my fuel go all over the place other than that I am real happy

I just pulled a pro charger blow thru 555ci engine off the dyno , used a CSU blow thru carb , they are the blow thru guys , took a lot of tuning !! , 23 pulls , jetting went from 76 to 92 in the rears , 10 air bleed changes , fuel system mods , went from 650 hp with a blow thru efi merc system , To the carb blow thru making 821 hp- 867 tq @5000, 4-5 psi of boost , 93 pump, a/f 11.9 , bsfc# 48.idle at 900. also we went away from the box system becouse of the problem jetting and if it floods over , you have a bomb . should be up on the website soon www.thunder-boats.com Bobby

Great info! what were the primary jets? and PVs front and rear?

I run a M3 only 5-6psi as of now, I talked to Patrick @ Prosystems, he did not want me to run without a box, as he felt there was not way to keep from blowing a small amount to fumes out thru the throttle shafts and in a enclosed engine compartment...not good...

ezstriper! So what configuration carb are you running.Is it set up for a box a blow thru or a stock type. JOHN SR