knocknbuoys

Hello all,

Im hoping someone can help me. I am currently rebuilding my mercruiser 260 for my chris craft scorpion. The block after running the numbers is a 80-85 4 bolt main gm truck motor. I am using a set of 906 vortec heads. Where i am lost is what would be a good size cam to use im not looking for a race boat but i want a little better performance. Also would a low rise or higg rise intake be the better option. Thank you to anyone who could guide me a little bit

Crude Intentions

iTrader: (1)

Get in touch with bob Madera. Rmbuilder on here I haven't used him yet but many claim him the cam guru and I have read great results from him.

Cam selection will vary greatly depending on exhaust valves rockers. Many things go in.

CC230

I started with the same boat and engine. My engine was an '86 1 pc rear main seal but not a 4 bolt or roller block. I ended up with a nice roller 4 blt main block. Then I got a set of Vortecs (did some head work), and ended up stroking it.
Bob Madera will answer your questions and help you with a package that will work for your needs. And your probably going to want an Edelbrock RPM Performer Air Gap intake.
Tell us more about the boat and what you do do with it.

sprink58

That's a lot of boat for a single SBC so your primary focus is torque. Go with the Comp Cams Xtreme Marine 264 or 272 roller kit. if the budget allows get a set of their Scorpion needle bearing roller rockers also. The Air Gap is a great piece...just make sure which ever intake you choose stay with a dual plane.I like the Holley or Quick Fuel 750 CFM Mechanical Secondary Carb for your application. Some will argue that it's too big for that motor but I'm running them in a pair of 355's with the same 272 cam and it worked out great. I'm a fan of Mechanical Secondary Carburetors for boats.

Your never going to see any serious top end from that package but if you want to add some seat of the pants zip to that rig...find a 1.65:1 Alpha drive for it and amaze your boating friends with the acceleration and hole shot you will have.It's sort of like adding a 4.11 gear to a truck that has a 3.42 differential.

knocknbuoys

Thank you for some input so far. I took the boat and totally redid it myself last year. New paint new interior and some other mods. I will post pics when i learn how to. Bit when it came to the motor i boight the 260 off a mechanic at my marina and everything checked out but in my learning proccess i didnt pressure check the exhaust system and it had cracks in it and ended up eventally cracking the factory heads. Fml lol the boat with gear and 4 ppl on it last year was hitting 45 on the gps with a i believe a 21p ss proo and a alpha one gen one . What kinda power could i expect i think i read the boat only wieghs like 3200 with a motor. I would be extremely happy with 55. And the boat has thru hull with stock mercruiser exhaust setup

CC230

Before my boat got sick, it would run 44-45 loaded, and with nothing but me and my Wife, 2 ropes and 1/8 tank of gas I saw 55 mph once, mostly 50mph, these were with a 19 pitch stainless prop. All stock, no through hull and not GPS though.
This time around I'm hoping to get 48-50 loaded and a solid 55-58 unloaded.
We'll see.

I'd like to see pics of your through hull though, haven't cut my transom yet!

knocknbuoys

Cc230 as soon as i figure out how to post them i will cause i would like everyones opinion on how they think it turned out. And honestly if i can get 55 out of my boat i would be so happy lol then i could keep up a lil with my buddys baja and powerquest ....

Trash

I highly recommend going the stroker route. The added displacement and torque will be appreciated. I can't give you specifics on what manifold or carb to run as I do EFI stuff, but I have had good luck with Crower cams too. They have some nice hyd rollers that work well. 220-235 deg @ .050" is about the max duration you'd want to go with stock-ish exhaust assuming you ran a 112-114 LSA without reversion becoming a factor. This is a very general guide but will put you in the ball park. There are other factors that come into play as well.

Keep us posted and good luck.