What Cam Do I Need?
 

I plan to pull the engines out again this winter to do some work in the engine compartment, and plug a hole for the A/C intake.

While out I want to change the cams in the engines.

These are Merc 500 EFI's (2002 Models)

Last year we freshened up the motors and replaced the stock heads with World Merlin II cast heads, and bumped the compression up to 9.1:1.

Tyler Crocket reprogramed the ECM's to add a little more fuel from mid to top end and we raised the rev limiters to 5550 RPM.

Other then that the motors are completely stock.

Some of you have said that I should have changed the cams to take advantage of the better flowing heads.

So now I have the chance to do it.

What is the cam of choice for this application to give me the most performance?

Thanks

Re: What Cam Do I Need?
 

Doc,

just out of curiousity, what kind of gains did you see?

Re: What Cam Do I Need?
 

How about the HP525EFI camshaft?
Should be worth a good 25-30HP over the 500 cam.
It will work well with the MPI and should be an easy program change.
May not even need a program change???

Re: What Cam Do I Need?
 

Which size Merlins did you go with? Are you going to stay with the 5550 as the max rpm?

Re: What Cam Do I Need?
 

BB-Chevy Merlin II Cast Iron Cylinder Head
320cc Retangular Intake Ports
119cc Combustion Chambers
2.300'' Int/1.880'' Exh Valves
1.550'' Valve Springs, .650'' Max Lift for Hydraulic Roller Cam


I don't plan to spin it higher than 5300 RPM.

Re: What Cam Do I Need?
 

Get cstraub or RNBuilder to cut you a cam.Don't buy off the self cam!!

The next step up on the Crane is 741 it has a lot of overlap and is at 112ls. Even on my blown apli I could of made some more power with a custom cut cam for my motor .But it gave me a little cushion when I put the 10lb pulley on it :eek:

Chris or Bob do have the specks on the 525 EFI cam , Wondering what it is????????

As far as the 500 efi and the 525efi. Besides the cam they also change the the heads and headers to get the increased HP.

Doc just go ahead and put you some Whipples on it. With that CR just don't spin it as fast.But the $$$$.


Good luck

Rob

You think the AC pickup might be slowing ya down??

Re: What Cam Do I Need?
 

From what I have read in other threads:
The 500EFI cam is basically a Crane 731 ground with a 114°LSA and the 525EFI cam is a 741 with a 114°LSA...

Those big sweeping headers on the 525 have got to be an improvement but, the $$... :eek:

Re: What Cam Do I Need?
 

I would think you could get pretty close on SOME of the off the shelf cams that are out there to day. Granted there is allways a better grind that can make more power , but 5-10hp? or more?Also differant manf use differant ramp profiles and cam timming. I think i remember the Ultradyne soild race rollers had a very steep ramp that was tuff on valve train,but made some good power :D

Rob :D

Re: What Cam Do I Need?
 

YES

I have seen a 2-3 MPH increase from boats that had them removed and put on the transom below the water line.

Thanks for the info on the cams.

Re: What Cam Do I Need?
 

:eek: :eek:

let me know how that turns out. Ill move mine.

Re: What Cam Do I Need?
 

DOC I have a isky cam with the merlin 310 heads 9/5 to 1 comp BG CARB dart intake 509 cu I made 600hp at 5050 rpms, 647hp at 5800 rpms tq 627 at 4800rpms :D the CAM I went over and over with them ,because the last cam my builder picked out sucked only made 545hp at 5200rpms didn't idle worth **** 110 lc new one has 114 lc if you want specs I WILL LOOK IT UP FOR YOU! :cool: ART

Re: What Cam Do I Need?
 

I wonder if this is slowing me down . Its a tru hull and has a 45/bevel so its resesed.Its flush with the bottom but it still has a opening about 1/2inch . What ya think????


Rob :D

Re: What Cam Do I Need?
 

no it is out of the water at 100 :D

Re: What Cam Do I Need?
 

Strip, you have the right kind. I have one of those stupid clam shell types that sticks down 1-1/2 inch! :eek:

One buddy replaced his clam shell type with what you have with very good results on a 33 Outlaw.

My plan is to just mount it on the transom.

You are good!

Dock

Re: What Cam Do I Need?
 

Totally agree. I wonder why these companies spend millions every year on R&D if they're not going to change anything? But hey, 600-820" motors were commonplace 25yrs ago I guess.

I have run both custom grinds and shelf grinds in different applications and have no complaints about either. Its all about what you're looking for, how much you want to spend, how long you want to wait, and if every ounce of power is important to you in a pleasure boat. The more unique the engine and combo the more a custom is probably needed. The more "tried and true" engine size and combo, the less.
A custom grind should make more power in either application, otherwise why bother. The real question is wether 5-10hp (in many cases with tried and true combo's) matters to you.

Comps solid roller ramps are also tough on vavletrain and that was a custom grind as well. :drink: This wasn't their fault, I wanted to get more aggressive than the custom Erson I had and it worked. Picked up 40HP and 20 ft/# on the dyno in 632" NA pump gas motor (not garden variety motor)......Didn't move the needle in the boat at all and broke a new lifter after 6hrs. Erson cam lasted 50hrs before changing out lifters. Ported and polished Dart 360 heads and tunnel ram. Comp was 280/288 @.050 .782/.760" on 115 CL. Erson was 272/278 @.050 .772/.750" on 114 CL.

Re: What Cam Do I Need?
 

Dock I guess they use that style so you can use it while running???

Good I didnt want to have to lighten up my load of beer to ajust for the speed loss :D

Mike your probaly right its probaly out of the water :evilb:

Rob

Re: What Cam Do I Need?
 

DOC thats factory water pick ups?? don't you have bravo's? with built in pick ups in the drive? do you get better water pressure with the transom pick up? no more Questioners :D

Re: What Cam Do I Need?
 

Hey Doc,
How are you?? Been a while.. and yes.. take that bump off the bottom!! Should see a 10 mph gain at least! Tell me they are not right in line with your prop center line??? Of course as big as that bump is.. it could be keeping water from hitting the props at anything over 60mph.. LOL.

I have no idea on your cam. But bigger is better until things break or you run out of flow, thats what they tell me... *S*

Let me know when you make enough power to break those drives and I will fix you up!! Take care my friend.. just had to jump in here to razz you a bit..

Dick

Re: What Cam Do I Need?
 

Hey Dick,

How's it going up there buddy? As for the cam I'm going to keep it simple and stay with the Crane 741. Nothing would make me happier to make so much power that the drives would be popping, but I would have to sell you more bearings to afford the drive repairs! :eek:

That brass A/C fitting is a joke. I knew from day one it was costing me speed, but could not really tell how much until I spun the props in. The fitting is almost exactly inline with the port drive. I could not get the port engine to hook up at all spinning the props in. I was going to relocate in entirely to the transom, but I like what Rob has pictured there with the Hustler. I may just replace it with the flush style. What are your thoughts on that?

When you going to head South for a visit?

Dock

Re: What Cam Do I Need?
 

It depends if the pickup causes any turbulence or causes air bubbles in the water stream in front of the prop. Best way to check it would be ride on the swim platform while the wife drives the boat wot... and see if you get and white water in front of the bullet...
Or just move it to the back and out of line with the prop!! Then you have a reasonable idea that it is getting clean water!!

As for the trip, well I would love to have a boat that runs. This motor is still giving me greif, maybe in the spring??? Oh yeah thats when everyone wants their drive done.. hmmmm !! Hey everyone.. send me your drives early so we all can head south in the spring to boat.. and see Doc!! :D :D :D

Dick

Re: What Cam Do I Need?
 

I would not be dead set on that 741. This is your chance to optimize your engines performance. It will cost you the same either way but I would rather have a spec'd cam versus a shelf variety any day.

PM Rmbuilder. I can assure you he has the knowledge base and track record that will get you right where you need to be.

Re: What Cam Do I Need?
 

i also would recommend getting a cam cut over just buying the 741. I think there a little more power to be had and not much price diff.

The reason I went with the 741 was I was trying to keep it simple because of the computer programing. I belive gave up some power on my combo.but it safe and reliable.I think I could of went with a bigger cam , The hp had started to tapper at 6100rpm

Rob