That's all going to depend on the rpm of the motor. You really need to do a velocity profile on the motor and see how much air speed the motor will need for the max rpm then you can select the proper head. My guess if you want to spin 6000 with a 540 you will probably end up between the 315 & 335 head. Most will say in that case use the smaller head. Being as you already have the 335's I would put them on and roll with it.

this is getting scary,that,s twice i agreed with you in one day,lol.

Careful. Before you know it you will be blowing up stuff running your boat into rocks and flipping it over.

After more reading and a couple of questions asked I have found the 114 degree lobe seperation version of the 741 cam is crane part #139671 . This is the stock 525EFI cam I believe but at a more reasonable price than from the Merc.parts shelf.

I have a 540 with AFR 315 heads that had a crane 139021 witch is pretty close to the one your looking at (112 lc). It was pretty much done about 5400 rpm.

Put in your info, get a custom cam based on your set up for cheaper than Crane. Easy


http://jonescams.com/marine/

.....

Really hoping that this will pull to at least 5800. Is your cam setup straight up or retarded/advanced ?

Straight up. Pulled it out and went with more lift 660-650 more dur 246-250 @ .050. I can tell you a 741 in a 540 will not pull to 5800.

To be clear I am actually looking at 139671 which is the same profile as 741 but on 114 degree centers. Also I am using 335 heads. What are you running for an intake ??