I run that same 264HR in both my 355 Vortec motors. I'm running stock Vortec heads with reliefs cut for Beehive valve springs.I also am running stock MerCruiser exhaust thru prop. the engines make great torque and have great dock manners.

Any roller with similar specs to the 264 HR will make you a great package.

^^^Good pick^^^^

Grind Number: XM264HR
Cam Style: Hydraulic roller tappet
Basic Operating RPM Range: 1,200-5,200
Intake Duration at 050 inch Lift: 212
Exhaust Duration at 050 inch Lift: 218
Duration at 050 inch Lift: 212 int./218 exh.
Advertised Intake Duration: 264
Advertised Exhaust Duration: 270
Advertised Duration: 264 int./270 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.488 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.495 in.
Valve Lift with Factory Rocker Arm Ratio: 0.488 int./0.495 exh.
Lobe Separation (degrees): 112

I'm running comp 270 marine cam with Alex's valve springs rpm intake with a 1409 carb and through hull its a nice working combo and sounds great i get comments from other boaters every time out about how good it sounds

Thanks Everyone. I am going to try the Howards Cam that I mentioned in the original post. Specs look really close to Mira Boaters Comp 270. Shortblock should be back this weekend hopefully. Then the fun begins.

Keep in mind, he has through hull. You have stock exhaust through the prop. I wouldn't go more than the XM264 comp grind, but that's a choice you have to make between averting reverting and maybe 10-15 hp.

Spoke with comp cams about the XM270HR cam, and asked about reversion with factory wet, thru prop exhaust. He said that it would be fine with stock exhaust. The XM270HR has almost identical specs to the Howard's Cam I am planning to run, with the exception of the Howard's cam being 114 lobe seperation. If the overlap is less, will that mean less chance of reversion?