Cam question

[jstwkd]

What size cam is everyone running...I am trying to get as big as I can without reversion....502 BBC
Thanks

[Havasu Hangin']

My 509's have 236/240 .632 112 LSA
However, if you have a Bravo, I'd also worry about an idle below 900RPMs so you can shift the damn thing without breaking it.

[1stepcloser]

I put one of them three quarter race cams in mine.
Really sounds cool. http://www2.***boat.com/ubb/icons/icon14.gif

[Havasu Hangin']

I put one of them three quarter race cams in mine.
Really sounds cool. http://www2.***boat.com/ubb/icons/icon14.gif
That's really cool!
Mine are just RV cams...
:D

[Raylar]

First, don't just pick a cam for a performance boat based on how it sounds! Camshafts are the real "brain" of an engine. Proper cam timing, cam lift and the valve event timing and durations are the key to great engine performance. Remember in a boat the engine is always loaded "straining" and a boat is never coasting like a car. As soon as a boat motor is put in gear and all the way to the rev-limit the prop on a boat is trying to stop the motor! Cams for boats should have designs that let the motor idle down somewhat smoothly to 650 to 700rpms so you can get them in gear with the minimum of "clunk" or damage to the outdrive or v-drive. You must take into consideration whether the motor is carbed or fuel injected. The cams for these two are always significantly different as are their designs. Compression ratio, desired rpm band, fuel system type, breathing differences in intake, heads and exhaust and horsepower and torque band goals have to be decided and built into a "good cam." Just take a little time to evaluate what you want out of your boat motor, what type of systems and engine part specs you have to work with and then consult a good cam expert or possibly another boater with the same type engine setup and choose a cam that will achieve maximum efficiency. Reversion in a motor is a condition that generally exisits when the camshaft design is creating a negative exhaust pulse during intake and exhaust overlap that is strong enough to actually pull or allow water in the exhaust system to travel back up and into the motor, with sometimes catastrophic results. All cams have some overlap, they won't work without it! The motor that has a proper high performance marine engine cam will generally not suffer from any significant reversion. Reversion generally occurs when the camshaft design is choosen with a "dart board" choice and is not selected with the factors above. Also remember that every camshaft design has special valve spring and sometimes special valve train requirements. Any good cam with a lousey valve train is an accident waiting to happen! Post your exact engine , boat and use specs here and some good cam experts will most likely help you in your selection. Stay away from over-simplified cam specs and selection, especially those you read in magazine adds. The power and performance you get from your motor will be directly proportional to the care and time you put into "designing" your cam!!
OK schools out!
Ray @ Raylar

[jstwkd]

Thanks guys....
Here are my specs
The Motor,Long Block
Gen VI four bolt main 502 short block.with forged pistons, forged 4340 steel connecting rods with 7/16" bolts, a 1053 forged steel crankshaft , Blue printed high volume oil pump , Dually 10 qrt. with windage tray and scrapper , Comp Cams XR300 Hr Hyd. roller cam shaft Exh. lift .254@.050/ .580 Int. lift .248@.050 / .560 lobe sep is 110, roller Lifters ,SST roller rockers, Comp cams stud girdeles, pushrods Complete valve train . Comp Cams true roller timing set ,Edelbrock 6045 alum heads ported and polished by R&R Machine In Napa Ca,Stainless steel 2.19" intake and 1.88" exhuast. An MSD complete marine ignition system.I am running a edelbrock TM2-0 BBC Oval Port Intake Manifold.And an 850 marine mighty marine demon carb.Aluminum Indmar center riser manifolds with 4" tips no muffler for know.Maybe adding a captians call later.
The cam I have in the motor know isnt going to work.I am looking at the XM284HR Intake is .230@.050/.547 exhaust is .236@.050/.547 lobe sep. is 112
I would like to get more cam for more power.I need my power band to be in the 5100-5500 RPM range
The boat is a 2002 225BR with a volvo duo prop.I would like to be able to see 70 MPH.
Depending on what RPM/Power I end up with will decide wich prop set up I need.It will be between F7s/F8s.The F7s will get me 5300-5500 RPM.F8s around 5100-5300
550HP will get me to 70 in this boat.well 68-70.600HP definatley 70-72.
Boat Specifications
11 Person Capacity 1583 Lbs 718 Kg
Fuel Capacity 58 Gal 220 L
Dry Weight 3800-4000 Lbs 1724-1814 Kg
Draft 18" / 32" 46 Cm / 81 Cm
Deadrise 18°
And yes I know i should buy a different boat.But the wife likes this one.Tons of room and she feels safe in itwith our son.The boat does come with a 425HP BBC if you order it.I am currently running a 330HP SBC and seeing 55MPH 5000-5100 RPM
The noise and the speed is just to help me deal with this boat.....lol
Its a tank...but rides like a caddy.
http://www2.***boat.com/image_center/data/520/281225BR.jpg

[Nordicflame]

Get ahold of Bob Lloyd at Full Throttle Marine.
He knows the Crownlines intimently and builds quite few motors for the few hot rod Crowns around.
www.fullthrottlemarine.com

[jstwkd]

Get ahold of Bob Lloyd at Full Throttle Marine.
He knows the Crownlines intimently and builds quite few motors for the few hot rod Crowns around.
www.fullthrottlemarine.com
Thanks Nordic...I just talked to him this morning...great guy....He says the cam I want to use should be fine.I was just wondering what the big HP guys are using.I can only see about 55HP and 600TQ out of this with my current set up.

[BOBALOO]

I think alot of guys are using the Crane 731 226*/234# @ .050 .587"/.610" for torque
and the Crane 741 234*/242* @ .050 .610"/.632" for uppr HP
I think "Party Cat" on the boards has a 509/ Merlin head motor with the 741 in his 26' Party Cat and he had it dyno'd.
You can also search Offshore Only for roller cams.

[jstwkd]

how are the not getting reverson with that second cam?
Thanks

[Kaos1]

I'm am by no means an expert on this matter so correct me if I'm wrong. I am shopping for a cam for my sbc and the tech at crane cams told me that reversion had to do with lobe separation. In my application he said as long as you have 112 deg you will not have any prob with reversion. Like Raylar said all cams have some overlap but if you have too much then you get into reversion. I do not think it has as much do do with lift and duration.