So just looking for some opinions making sure I'm not over doing or under doing it here... looking at building a 572 with an m3... so planning on using the dart m block.. afr 357cc heads.. havent decided on pistons yet as one guy I talked to said do 9:1 compression and the a could others said to keep around 8:1... also think about going solid lift cam... just planning for the winter project so trying to get a bunch of opinions on what all to use.. all the do and don't... I know there is alot of different answers but trying to get as much info as I can.. any help be appreciated

The M3 is pretty small for a 572, 9:1 works well, solid roller on a 112, AFR heads are good, what is your HP goal ?

Roo, I see that you are new---welcome to the forum. Do you have a reputable engine machine shop for your project in your area?

I do not know how much you know, but power adder systems that make boost can usually hide a lot of mistakes and cover a lot of "sins" compared to a Naturally Aspirated engine with a smaller window of choice when it comes to parts selection. That being said, NA engines are more sensitive to cam and head selection compared to a blower engine that makes a lot of instant power almost everywhere--- but a little more careful thought needs to go into selecting a cam profile---it is a little more critical to get the cam profile correct almost like you would for the attribute of a Naturally Aspirated engine--- they're more sensitive to cam and head size, etc..

I do not know much about Pro Chargers, but from what I have gleaned over the years and seeing some Pro Chargers built destined for marine usage, they tend to have some slight "delay" or "lag" as they kind of spool up building boost like a turbo does----not like the instant response of a roots or screw type/Whipple supercharger systems. However, the Pro Chargers Do work very well once they're spooled up.

, but If it were me, Pro Charger application or NOT, I would always stick with a hydraulic roller cam for ease of maintenance and stay on the smaller side of the cam duration profile---and stay away from the temptation of going with a BIG cam.

It depends on your application and what your goals are, but if you are going to make a mistake on choosing a cam profile, then it is better to make the mistake of choosing on the smaller side of a cam duration/profile. At least that is where I would start with a cam---especially for a Pro Charger.

Also, this is just me again, but an AFR 357cc head sounds a little too large for a 572cid engine for marine use under 6000rpm---will it still work? Yes, but at the expense of mid-range Torque especially as a Pro Charger is spooling up and needs some assistance from the cam and heads that work better down lower in the mid RPM range to give it a little more kick. I tend to believe you would be better off with an AFR 335cc Cnc'd size head design vs their 357cc size---but AFR is an awesome head design company so you have a good head company to begin with.

Personally, I do not like or care for how a Pro Charger system looks under the engine hatch of a boat, but they Do make power---they're runners !!!

Okay, so here's my disclaimer----You can/will get 101 different opinions and suggestions on this website. There's a lot of ways to skin a cat and my opinion could look like the proverbial "poo-poo platter" compared with someone else's input on here and rip me to shreds. I am NOT an engine builder...just an old retired, Marine hi-perf enthusiast who loves boats/BBC engines and has witnessed a lot of marine engine stuff in my life. So, it does not mean I am right or wrong---it's just my own .02 I hope your project goes well and you meet your goals.

Well I wouldn't say I have particular goal in mind... I not looking to set any records just want good reliable power honestly... I figured the m3 would be alittle small but again not looking to run on the ragged edge... and when I first thought about this engine I was gonna go with a 335 afr head but the guys at afr said that he really believes the 357 are the best choice...

Roo,

If I'm spending your money....

Molnar crank and rods, JE pistons and AFR heads. I don't have a clue on specific numbers, just going by general consensus on quality of parts.

On the ProCharger... Owning one myself, I'd suggest exploring the Whipple option. I'm not totally pleased with how the boost comes on with my ProCharger. I have the M1 3lb kit that ProCharger developed specifically for the Merc 496, and It works well enough, given that you can't really pour any REAL boost on those damned cast pistons, but I'd much prefer the boost come on a bit earlier than 4200 RPM, given the engine maxes out at 5K. I'm still at negative manifold pressure at 4K RPM. In my case, it's probably for the best, as I'm still running this through a stock B1 outdrive that I don't really want to blow up. Your results might be a bit different with the M3, but, seeing the comments here about it being a bit small for a 572, I'm thinking it won't be much. If I had my 'druthers, assuming you're already either running a sturdier outdrive or are planning on it, I'd much rather have a more linear boost curve. Take this for what it is.

Thanks. Brad.

My m1 on my 509 I have at the moment doesn't take that long to build boost... I mean if I am cruising down the lake at 3000 rpms I'm not into boost but if I give it throttle it builds it instantly... myself personally likes the procharger... I haven't had a Whipple I hear they are super nice pieces... like I said I'm honestly not looking for tip top every last little but of horsepower... but I Wan good reliable power is what I'm after

I'm not sure a about proper Pro Charger sizes with any given engine size, etc... but I agree with Brad and would personally rather select a Whipple over a Pro Charger. A Whipple makes instant power and look much like a Roots type of blower under the hatch and gives it more of the "cool look" factor,

There are lots of factors involved, money, personal goals, application.etc. Some guys prefer to pick out a HP goal first and it is just another option about how to make your power goals, but I am kinda the same way you are about my power goals and try to realistic about it.

I'm not racing, or looking for every last drop of HP I can get out of an engine or trying to break any speed records or set the world on fire, and somebody somewhere is always going to be a little faster than you are.

So, my outlook is I just try to keep it relatively simple and just want good, efficient, reliable turn-key power and I think it all begins with the amount of cubic inches being used (what $$$ you can afford) and try to build as best as you can from there off of that. For the most part there's reliability in Cubic Inches.

I like to make good power and aim for a peak RPM number vs horsepower figure, but it all depends on the combination---engine CID, heads and cam. Most of these kinds of boats top out between 5000-6000rpm range.

I usually try to pick out the RPM range at peak power and let the combination of parts basically dictate what kind of HP it will make at that RPM---whatever that HP number may turn out to be.

Without a goal, you can make an easy 750 with a NA motor that size. The M3 will have to spin faster to match an M4, and make more heat in the intake. The new Prochargers spool faster than the old ones and they don't die at top end like some of the other brands. Do you want to break the vert shaft pulling out or peel the face off of the gears at top end.

My buddy had a procharger , had to put the stick to the wall getting on plane, the thing sucked, made no power at low rpm and getting on plane was a joke.
Good luck thou.

Roo,

This was my general experience. It's really not that bad for me, though. At the end of the day, I *AM* pulling more prop and running faster than any NA PQ280/496HO I've ever heard of, but only by a little; 28P, instead of 26P and 76MPH, instead of 65-70. I guess it is inarguable that I am stuffing more air through the engine than I would be NA, boost or no boost on the gage. In my specific case, I really can't do much more than that, given the cast pistons and stock Bravo outdrive. But, when I have to pull the engine for a refresh, we will be correcting the piston issue with JEs, and, if we ever have any real issues with the drive, it'll be replaced with an SCX. Then I will be looking to replace the ProCharger with a Whipple, seeing the success Kallucca had with his Checkmate 280ZT.

The major malfunction I see with ProChargers is that they have all the disadvantages of turbocharging, with none of the advantages of a positive displacement supercharger. With a ProCharger, at low RPM, the air really doesn't HAVE to go down the intake if it really doesn't want to, so any real boost waits until the RPM gets to a point where the air doesn't really have that choice. With a Roots or a Whipple, this isn't the case. The air has absolutely no choice but to go down the intake. The end result is a more positive and linear boost curve. At the end of the day, it seems considerably easier to build a strong, reliable engine with a positive displacement blower than a centrifugal, and I suggest a Whipple because it takes up essentially the same space as a standard intake/carb would. Kallucca was able to tuck one under the sundeck of his Checkmate and is pulling ~950HP. You wouldn't have to push it that hard, and still have plenty of HP, only it would be present throughout your RPM curve, not just at the top.

Thanks. Brad.