What cam did the Merc SC525 run???

I have a 7.4 with a b&m 174 and she is out for winter and to get properly setup for the blower and i figured i might as well do a cam change if i can get some more HP out of her.

Is there a better cam to be runnign than the one that wa sin eth sc525?

I am running CMI headers and custom tailpipes taht will be pretty much dry except for some H2O mixxing right before the tips at the transom. (fully dry with H2O exitting seperate from eth exhaust was just to damn loud!!!)


Also i am running a dominator 1050 I think it was SUPER rich last year (only ran it for maybe an hour so i didn't get good test time) What wodl be the proper setup for this carb for my engine (i bought it with teh blower and it was supposedly refferenced to the blower adn engine setup)?

Puder,

Did you do any ignition upgrades? I found that what I thought was rich condition, was cured immediately by adding an MSD box to the merc V6 module...

mmmm well i do have 2 msd brain boxxes just chillin somewhere in my garage....

I have a thunderbolt 4 witha 24* v-6 module

how do i hook up the MSD with the tbolt4? I bough the brain boxxes about a year ago thinking i was goign to use them on a project boat that never happened. I weas goign to run the full MSD setup.

I tihnk i am runnign rich fora few reasons. The plugs looked funky after only and hour. After installing a blower and teh new carb I saw little if any gains and my exhuast was running SUPER hot. My tailpipe were totally dry (no h20 mix) and they got so hot at one point they were glowing a tad. It was night when i ran it so i could see them glowing.

You would hook them up like the points style diagram in the MSD literature. Basically, the two wires from the thunderbolt module that go to the coil now, would go to the MSD box instead and the MSD box would connect to the coil. It only acts as an ignition amplifier. Also, you would need to remove any other wires that currently go to the coil. They go to misc places. The MSD box is the only thing that connects to the coil. I can send you the MSD wiring diagram if you need it.

My new motor would foul the plugs in 2 miles of running on a new set of plugs. Not just a little fouled either! Not just at WOT either, 2500rpm. This never happened on any other engines I have ran. I kept chasing down carb issues, but they were new Nickerson units. Couldn't see how they could be that far off. Him either. Finally pulled the motor and put on the dyno. Should do that at all COSTS!!!! Added the MSD box and the torque instantly gained 30 lbs. Tweaked from 30 to 32 degrees of timing and gained 60 hp. All told we found ~75hp in an hour! Also saw what the hp and torque curve looked like (different than I thought it would be for the cam I was using) and realized that I had made a mistake changing to 1.36 gears (ears are burnin). The motor made it's max power at 5900rpm instead of 5500 like I thought it would.

Ate up all summer doing this. GO TO THE DYNO!!

Wouldn't hurt to send your carb to someone who knows what they are doing. If it is a old Nickerson unit, get the stamped number off of it and give him a call. He can look it up and give you advise.

if you could e-mail me the wiring diamgram I would be super appreciative.

My coidl is lookign kind of old and funky shodul i replace it with the msd one? And is there a specific marine version i should get or will a car one work fine?

The MSD box is actually spec'd to use with certain coils. It puts a much higher primary voltage on the coil. I just happen to have a new MSD blaster coil still in the package. Made a mistake and ended up with an extra a long time ago. You pay shipping and it's yours. I'll also look through the manual to see exactly what you would do with any extra wires on the coil. What year is your engine package originally? What model MSD box do you have?

puder, the Merc 525sc cam is Crane #132561. Its a flat tappet with 228/236 duration and .530/.551 lift on a 114 lobe separation.

MSD 6M-2

brainboxxes. I would gladly take that blaster coil off your hands.

my address is
71 buckram road,
Locust Valley NY 11560

what is your address?

I'll get it out today. I took a look at my seloc manual schematics and it looks like you would simply lift all the purple wires off the coil as well as gray ones, how ever many, (keeping them together) and connect them to the input of the MSD box. Then the MSD box output goes to the coil. One of the grey wires is for the tach. Many other things (sensors) might use an additional purple to get ignition 12v power from the key. I had to go through this some time back with the engine on the stand and completely took the wiring harness apart to see what was going on. Many changes since the harness oriningally came on a 7.4L with knock module. That's why I can't exactly say how many other wires will be on the coil, but they all stay together and act as an input to the MSD box. BTW, my MSD instructions are for a 6AL. They might just be the same though, but I forgot to bring them in. I'l post tomorrow what the hookup is.

I Don't think you will have a rev limiter with the 6M2 box and the Merc V6 module.....

Have you thought about having your motor dyno'd? It's very informative to be there asking questions and learning what works and why. It also helps to know exactly what the motor is capable of and where rpm wise when the motor gets back in the boat.

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Puder check your email

I hope this helps