Got the same boat had a xr on running about 950 hp in it blew too gears with 4 hours on rebuilt drive😡 The problem is our boats are heavy but ride like a Cadillac I've since went and put a scx on it lost ten mph Gona mess with spacers on drive to start. I'm running a 540 on 5 psi with afr heads with two fast throttle bodies mane we get together on ute lake my casa best of luck to ya

Great post. More power means more stress on everything. Get ready to upgrade the drive unless the boat lives on the trailer. Going fast is expensive and fun!

How much hp do u you guys think I will have ? I have stock 500hp ,aluminum heads, chiller,420 mega blower,525 efi cam , cmi headers, 2 750 s planning on 7lbs boost

hard to guestimate your power without more information.what aluminum head ,also don,t know what ratio you are turning the blower at.

What size pulleys to run 5lbs of boost 420 mega and chichiller I want to start off small to break in or what do you guys recommend i should do . Could i use my pulleys from my 250 mega it was set up at 5lbs .

Pulleys from the 250 don't bolt on to a 420. The 420 takes a 6 bolt , 2 inch register style pulley, like a 8-71, 10-71, etc.

Are you using a serpentine style belt, or cog style belt? With a chiller on a stock 500, I'd probably start around 1:1 ratio, for around 5lbs.

My old setup was 7% under, and made about 6.5-7psi on my 468s without a chiller on my 468. Made some changes to the engine, and installed a superchiller. I started at 1:1 ratio, and it made 6psi. Went to 8% over, and made 7.5lbs. Went to 12% over, and made about 8.5psi. My engine is a smaller, but also has more cam, good flowing heads, etc, so those numbers should be comparable.

Intake air temps with that setup, with 6lbs of boost, were only 20 degrees above ambient, about 95 degrees in the plenum. 8.5lbs, it was about 30 deg over ambient, at 105-108* at full boost. Contrary to what the internet says, not ALL roots blowers make tons of heat, if sized properly. A 177 blower making 5psi on a 502, is a world away from a 420 or 871 making 5psi on a 502.

Focus on a good fuel and timing curve. Those two things being off will kill an engine much quicker than a couple psi of boost.

I have have good flowing aluminum heads,cmi headers,good cam . i have the 525efi cam heads set to the cam. Can i run 91 octane and some octane boost? What brand is a good octane boost . my boat holds 110 gallons not trying to break a fool every fill up. It is a ribbed belt also was need help with pully sizes to run 5 lbs boost. Thanks for help

Finally ran today ran good up to 3000 rpm kicked it to 4000 rpm running 50 and I only 2 lbs boost then started blowing oil through air breathers . Shut down motor and there is a noise like air passing through valves pressure like. Did it lean out? Never popped . Starts right up good oil pressure. Any ideas ? Any info would be very helpful

Run a leek down test on it

Blew head gasket