its a 25 tantrum.can you tell me where the water pressure gets it's reading from.my water pressure gauge never worked.i traced the line from the gauge to the motor tonight.found the end of it handing near the bottom right of the motor but no fittings that i could see

Upgrade the cam to make peak power in the 5,500-5,800rpm range, put on an Edelbrock Performer RPM AirGap intake and get a set of stock 496HO exhausts (restrictor removed) to improve of your 454's log manifolds.

DTDyno shows those changes will be a pretty large jump in power - as in 444hp at 5,500rpm.

Its May .....enjoy the boat .... prop tuning is ok ...but if you had a light load ...your prob ok ...with more people and fuel the RPMs will drop ..if you prop it for top end with you and 10 gallons of fuel, when you and your friends are out it will labor ... I pulled my motors on Jan 27 for 3 weeks ...well everything is still in pieces ..... enjoy the summer ...m

That's the best advice on here. Winter, not spring is the time to be rippin' your engine apart!

I agree. At this point an aftermarket exhaust system would be something you could at least add/swap within a couple days (if you wanted to) without too much trouble and still enjoy the summer with your boat. Save the major/internal mods for the winter.

i turned 5100 rpm with 2 people and a full tank.it was 60 outside i may loose some when it gets 90.gonna throw a 25 labbed mirage on it this weekend to try.should be able to make 550 hp with a 496 right

Just my $0.02, but your Mag already has a solid bottom end - forged crank, 7/16 rods, forged pistons - so your $$$ will make you more HP by working on your top end. Get a great set of heads, a decent exhaust, a good intake and the right cam and you'll have your 550hp with your existing bottom end! No blower, no juice, just nice reliable naturally aspirated power!

Don't mean to bust in on this thread, but I like Eceptor's advice. I'm just wondering about the same additions to my 502 EFI. I've already upgraded to a .550/.572 cam and .25 longer rods during a recent rebuild, just not sure about how much I'll benefit from a good set of heads with Merc injection?
I'm told this setup can have it's limitations.

drive it stock and enjoy boating or would rather be a mechanic. Never had a problem with a stock boat

Rod length has little to nothing to do with power production.

If I had a 502mag with a solid bottom end, I'd put either a set of AFR 305's or Canfield 310's with a nice single plane intake and a cam that would let the it make peak power right at 6,000rpm.

But that's just me...