HI I WOULD LIKE SOME INPUT FOR BEST CAM AND INTAKE MANIFOLD FOR 502 CI. I HAVE GEN IV 502 LONG BLOCKS WITH MERLIN 310CC HEADS POCKET PORTED, COMPRESSION RATIO IS 9:1. SPEED DEMON 850CFM CARBS AND MERCRUISER THUNDER BOLT IGN. I NEED SOME INPUT ON HYD ROLLER CAM AND INTAKE MANIFOLD SELECTION.
THANKS.

I have the same motors and heads has 13951 cam and gold
rockers sounds kick ass with stelling dry headers idles at 950 and runs great up to 5500. May be a little much but i love the result. greg kc

TTT
Thought there would be more response to this thread. I am also real interested in what everyone else uses. Spoken with Crane & they recomend their 168731 cam (int-587 Ext-610, duration of 226/236) with a single plane intake & 800 Cfm carb. kinda of close to what the HP 500 uses, just a little less conservative.
Good luck John

Forgot to mention...I wanted to use Cranes 139741 cam, they claimed the 168731 would work better because of the 8-75 compression. They claim the 741 works real good once you get above 10-1 CR Who knows?

741 is a lot of cam.
731 is a great cam. Must match springs with it.

39 is a heavy boat. Might look to the 731 cam AND an RPM Air-Gap dual plane (you'll lose 10 hp off the top, but you'll have noticeably better torque to get on plane - don't forget that you'll be probably going up in prop pitch with your extra hp which will sap some planing performance). Not arguing with the Dart single plane crowd, but the AirGap proves to be an awful good intake.

If you don't like their 1st answer, call again later.

Crane told me that the 741 is better suited for the 502's, and the 731 is for the 454's. I went with the 741. 2 yrs and all is good.

US1
Yeah, 741 is probably better for a NA 502. 731 is better for a blower 502. I just figure everybody will end up with blowers eventually. Kind of clouds my judgement...

Agree 100 % on who you talk to. I like the 139741 cam, everyone that uses it is happy. The last Crane tech said " oh yeah it may work but you need atleast 10-1 or higher CR". Merc's Hp 500 Cam is a little conservative for what they use, guess they want their motors to be bullet proof. Too many different selections, mind boggling choices. There again maybe a conservative cam with a blower is the way to go???

Mine was blown.
But, 27FOUNTAIN has the same blower, same boat and basically same motor and is running the 731 with same results as me. With that said, the 731 may be a tad bit easier on the valve train.

I have the 741 in my 509..ran it with an air gap intake and had too much low end torque for a light boat. (620 lbs @ 3500) A heavy boat would like it better I think. I'm in the process of freshining and now that I'm in salt water going with the Merlin single plane with inserts to move the tq. up some. Little more CR then you 9.8-1. Idles good and so far no issues at 100 hrs.
Dan