Repairs and Maintenance > Engine Repair/Maintenance - All Ski Boats

Anybody have a favorite cam for an Advance?

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Andrew:
90% sure I’m going to rebuild the motor this year in my Advance. It’s got a 94 Mercruiser 350 ‘mag’ motor in there now. I’m not going to go crazy on this thing, but would like to get a bit more torque on the low end. Don’t really care about anything over 4,000 rpm.

I’ve got a quadrajet, with the ‘mag’ intake, essentially the high rise Chevy z-28 manifold. The guy at my local ‘speed shop’ ( surprisingly there is still one left in my town) tells me I should stick with the intake I have - so guess I will. It’s a pre-vortec motor, so while I’m sure I could pick up some torque by converting to vortec heads and intake - more $$$ than I want to spend.

The oem cam for this motor is pretty mild, 200 / 212 duration, 400 / 410 lifts.

Thinking of going still mild with a 212/218 but might go up one more ( 218/224)  Curious if anyone has been down this path with this hull, and has any advice ? Thanks.

backfoot100:
Marine cams are mild as far as cams go.
Not sure how much you'll gain with just a cam. Seems like a lot of work for very little reward.
Is the factory intake cast or aluminum? What HP is it
rated at? 260? 285? 300?

An internal combustion engine is an air pump. The bottlenecks are carb, intake, head and then exhaust. You increase the airflow at one point and its only as good as the next bottleneck. As a general rule these engines in stock form have crap intakes and heads.  I really don't know what a cam will do for you with the crap heads. My personal opinion is put new intake and heads before a cam but thats just me. I put heads and intake on a bone stock 351 that bumped it at least 30-40 HP and never touched the cam. That was in a buddies 80 Correct Craft. It was a smokin 53MPH barefoot boat after that.

The QJ carb is good to 750CFM. The factory does a good job of setting them for a specific engine and application. At least in the automotive world. As long as you keep the engine pretty much stock the QJ is fine. Modify the engine and any QJ carb adjustments are a PIA.

I built a 400 HP stroker for my barefoot Advance and it runs strong so the hull and tranny will handle anything you want.

Andrew:
I’m not doing the rebuild just for the cam - I bought this motor , used, and ran it in another’s boat for last 12 years. It’s always run well for me, but there has always been a lot of ‘blowby’ smoke coming up through the valve covers and routed back to the flame arrester. Never bothered me so much when the motor was 10+ feet behind me in an engine room.  But in this boat it’s more of a problem, when I get off the boat, I have the smell of burning oil exhaust. 

So while I’m got it torn down for new rings and bearings, doesn’t make much sense to reuse the 25 year old cam. I believe my 350 mag is rated at 300 hp.

My machine shop guy is a boater, and seems to know what he’s talking about. I told him i want to boost low rpm torque, don’t really care much about max rpm or speed. Told him I was thinking about replacing the crank to make it a stroker, upgrading to vortec heads, or perhaps both.  The vortec heads is a good upgrade, but I would have to replace my intake. So far both the local machine shop and speed shop have told me not to dump my intake, which is a cast version of the z28 gm intake; supposedly it’s a good one. He told me the stoker upgrade is a nice one, but really pays off in the top end. So probably not a great choice.  He said my best bet is to up my cam a bit, and gave me the name of a guy who will tune my carb to match  the motor. But he didn’t have any specifics yet on the cam. And he was more used to building ‘go fast’ motors with performance exhaust.

Andrew:
What are you doing for exhaust on your stroker?

backfoot100:
Seeing as you're tearing it down anyway then I agree that a cam couldn't hurt. I think either one your contemplating would work fine. Neither one is radical by any means but going any bigger starts to push the torque curve higher up the RPM scale and you'll start losing your bottom end. Talk with a cam vendor to get help on which one. You have to be a little careful about water inversion when talking marine cams too. I put a Comp marine cam in my stroker and am very happy with it but its also a roller and not a flat tappet.

@Andrew
I have a stock aluminum logs with 4" SS tubes straight out the back, no mufflers.

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