SBC/Marine guys.. Cam ?

slideways

slideways

Club Member
So I'm shopping for a new cam for the boat since the onld one got wiped out and I'm not really sure along what specs I should be looking for. I want something that sounds good at idle (3" thru hull) but is relitivly mild, The motor is going to have a stock intake and the stock q-jet rebuilt. 21ft sea ray. stainless prop (honestly not sure what pitch) the boat never saw over 4500rpm last year, and it was in need of some more under the curve power to get up on plane when loaded up with 8 people.
 
Nobody? What would good cam specs be to make alot of under the curve power from 2000-4000ish, with a decent idle?
 
slideways said:
What he said. boat sever saw about 4500
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Well, I was a drag boat racer for 15 years, and my cams were ground for mid range torque and top end. These were roller cams as well though. For what you are doing here, you may want to go to a hyd. roller cam for durrability reasons. Picking the cam for your boat is very similar to picking one for your car, wheraas you have to look at the prop pitch, intake and weight of the beast you are trying to plane. I say similar to a car because tyou are matching convertor, gear ratio, intake etc. to work together within a given power band. You do the same here.

I would start with the Mercruiser stock cam spec. for that engine first. After you determine what they put it it to get it into the ballpark, you can go up a few profiles to wake it up a bit. Remember it runs at a constant rpm for long periods of time, so you don't want to polverize your valve train. If that is tired, you will find out instantly your first trip out.

I hope this helps you a little. Good Luck!
 
Comp has some marine cams, I've looked thru a few of them.. let me dig up the specs. It had a non roller hyd cam in it and thats what I would like to stick with. The motor will be new from carb to main bearings so no worry of tired valvetrain.
 
vented has like a small hole at the front of each blade. mercury has diff size plugs to change the hole size. Kinda acts like a stall convertor
 
Biggest I would use in stock motor.
http://www.compperformancegroupstor...=CC&Product_Code=12-236-3&Category_Code=HFTXM

If the boat is heavy go with this one.
http://www.compperformancegroupstor...=CC&Product_Code=12-232-3&Category_Code=HFTXM

If you use the bigger cam to get the idle lump, but you find yourself struggling to get on plane, you can always look into a 4 blade prop. You will lose 2 to 4 MPH on the top end but plane speed will lower significantly. I had an underpowered 18Ft and with 6 ppl and cooler it struggled to get on plane with a 3 blade of a few diff pitches. Went to michigan prop guy suggested 4 blade. I installed went to river and with full load plane speed went from 18 to 11 MPH and i only lost 2 MPH.

Sorry for long winded response....just food for thought!
 
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