Ok. I am wanting to rebuild both motors this winter. What HP should I want?? I am wanting to run 70-80mph. Stock are 420HP and runs 55 or so with Mirage Plus 23p. Also TRS drives. 87 415 Stinger. Also what RPM should this motors turn? Trimmed up and running I am running around 3200 each. That just seams low. I am use to smaller boats that run 4-4500.

Thanks

Mike

You have too much prop. My 1983 39 Scorpion runs 73-74 with 630hp 540's. TRS drives and labbed 21 pitch (22 final) props at 5700 rpm. When I had the 420's in it I ran 19 pitch props and ran 56-58 at 5200 rpm. I believe your 87 415 is about 2200 lbs heavier than my 83 390.

I think it will take around 700+ hp to see at least low 70's, open the wallet!!

It takes alot of azz to get a big straight hull to go fast!

Who would be a good company to call and talk about props with? I am also changing the exhaust out for weight and the heads. I am thinking those two things would total 500lbs less weight. ( I dont have the number in front of me but the exhaust manifolds are heavy) These boat have been around awhile and I am learning as I go. I would think someone would know this motor /HP these props you get XX Mph

Thanks

Mike

Mike,

I've got a set of labbed 22p Kiekhaffer (per the PO) clevers for CR drives that you can try out. They are 15" diameter. You're close enough to me that you could call me up on your way down to the Ohio and I could meet you there to help you try them out Okay, that was a shameless plug for a boat ride on that monster of yours. If you want to try them you are welcome to do so. I've got 300 bucks in them and if they work out for you they're yours for the same. The bird poop on the one is free Seriously though, a little elbow grease and they would look like new. They are in excellent condition; just a little dirty from sitting around in the garage. What looks like scuff marks on the left prop is actually residue from where I had the thrust washers duct taped to it. Let me know if you want to try them out. Bill

Hey-How'd your Dale Hollow trip go? Neat Avatar-That boat looks great in the water!

You are running only 3200 rpm at WOT and get 55 mph (on a GPS).?

That is a cruising rpm, and with 23" pitch and 420's you should be at 4800-5000 WOT. The 420 is a dam good engine, beefy internals and can easily support mods to 600 hp.

The 55 mph sounds right since the 415 is a heavy boat. check your tachometers.

Wannabe

We blew a head gasket about 2 months ago. Took one motor out and had it rebuilt. 4.25 stoke Alum heads. new intake and BG carb. Builder claims 630HP. I think the C.I. come out to 496. put it back in the boat ran took it for a run. That is when we were getting. 55 with a 420HP and 630HP both motors were about the same RPM. we did not have a GPS. We were wanting to run the boat at least a few for times before rebuilding the other motor. Well while we were out running around the new motor started to knock... Not a good day again!. Took it back out and and took it to the builder. Come to find out the valve seat came out. So its all getting rebuilt again. This time we are going to Dyno the motor and get real numbers. The only thing that was is the same between the new and old motors is trans, drive, and distribitiors. ( Old points system) we are going to change it to the new mallory system. So we keep thinking do we want to go bigger again. We keep hearing with about 650HP with right props 70mph. I would be happy to see that. Would anyone want the parts from an 454 420HP?? I have all but the block and pan. I will have 2 the same way or keep one together and sell just the parts from the other one. Email me if interested [email protected]

A couple of things here. Your tachs are way off, there is no way to run 55MPH with 23P props @ 3200 rpm. Your tachs must be way off. My 40FT Excalibur Ran 56MPH at 5100RPM with 23P mirage props.

Secondly, find a new builder. To get 630HP out of a 454, or even a 496CI for that matter, is very hard to do, unless you are running huge cams, and spinning them to 6000RPM. I see too many guys take their boat motors to a car engine builder, and waste nothing but money, and end up with a broken motor time after time.

If your goal is to work over the 454's, yes stroking them to a 496 is a good start. Aluminum heads ok, but the 420 heads can work ok too., hydraulic ROLLER cam, do not go too agressive on duration, if you do, you will need full dry exhaust. Those point distributors really need to go. Also, keep in mind, you will need a bigger oil pan, upgraded oil cooler,the stock 5.5 qt pan from the 420's are not really a good idea on a 550HP motor. Which is where you should be shooting for with a reliable 496CI marine motor. For 630 real world marine HP, you need a 540CI for a reliable N/A motor.

I see you are from indy, there is a shop up here in my area, who is also a great MARINE engine builder. He will build you a pair of RELIABLE 496's, using the right part combinations that work, no guessing.

www.atecoengines.com Tell Bill that Joe Garofalo sent ya, he will take care of you. He built me a carbed 540CI that made 600HP, and behaved like a stock EFI 454 mag. Good luck