We've got an Ebbtide with a 350 Mag MPI that is in need of some bolt-on goodies. ATI makes a bolt-on centrifugal supercharger kit for this motor, and Whipple makes a twin-screw set up. The guy at Whipple tells me to avoid centrifugal units since they don't create their rated boost until way higher RPM than do the twin screws. I thought 'chargers created boost from idle on, so is this guy full of it or am I?

I would imagine that any of the supercharger manufacturers are going to try to persuade you to buy their product. I also think each of them makes a quality product as long as you understand the limitations of their systems as well as your own engine's capabilites and limitations.
From what I understand the Whipple and the Procharger systems are both the easiest to install and the easiest to maintain.
There are many threads on this subject that can be accessed by doing a search.
Good luck on your quest for performance.

wasting your money putting a blower on that boat , really not designed for big power. if you really want more power the best alternative is to find someone in your area and have a
383ci stroker motor built , and upgrade your drive , good luck and welcome to OSO. ,

I agree...thats like puting nitrous on a Scion, just buy a sports car! I would sell the Ebbtide and add the money you were going to spend on the blower to get something faster. If you add the blower I guarantee you will only be satisfied for a very short period before you sell it to go this same route anyway. But you will not get the money you spend on the blower upgrade back out of the boat.

One thing you want to understand is, "how the engine was built to run". My 605 cuin doesn't make any boost until I get over 4500 rpms, that is by design. I would rather run on the cubic inches of the engine while at cruising speeds and only use the super charger to boost top end speed. BTW, I use a roots style super charger, tried and true. I've too many people that have taken the Whipples off their boats because they weren't satisfied, or couldn't get them to run properly. Do yourself a favor, like everyone else said, get a different boat that is a little more performance oriented and go have fun. That's what ALL this is about anyway, HAVING FUN on the water.

Robert

Hi Tonto. Long time no chat!
My Cigarette also uses Roots superchargers and it's set up to run at zero boost until over 4000 rpm. I'm happy with them but they do add to the overall engine height.

Here is my two cents: It takes torque to move ANYTHING. Car, boat, truck whatever. The Whipple will give you the right now low down torque that it takes to get a boat up on plane quicker and have that surge the we associate with big power.
I have twin Whipples on a 11K lb boat and it planes out in 2-3 secs. I know my drives are doomed but I don't care.


Smitty

I have Prochagers with my twin 350 mags and love them. I agree with what is said above, great mid range and high end. But thats where you cruise anyway.
I am sure Tom with Crownline 350 mag with the procharger will chime in, he has his running 70mph. Build what makes you happy, if you want to play with your boat and can afford it go ahead.

I'm biased towards Vortech...........

I don't have a kit for that engine so I'm not selling here, but I do have to comment about where the boost kicks in.

Whipple is always talking about boost curves when the important point is how much power can the drive stand without blowing up, or the prop absorb without blowing out. Guys running Whipples successfully will tell you that you have to be careful with the throttles down low. You can get on plane with 1/4 throttle in some cases; use more and it's hard on the drive. If you can't use it, the extra boost off idle really isn't an advantage.

The same boat with a centrifugal supercharger will need more throttle opening to get on plane because the engine is on it's own just off idle. For this reason it's not possible to overload the drive getting on plane. Now, if both boats are cruising at 3000 RPM when the "race" begins, my money is on the centrifugal.

We just converted an 8-71 555 CID engine with all the good stuff to the Rtech centrifugal system. The boat is 7 mph faster and the owner says it has never accelerated this fast before. And it planes the boat just fine with a full tank and four big guys on board. As far as idle quality and dock manners there is no comparison, the single Nickerson carb is a dream. It's just a different supercharger combination that some people like.

Sorry, I started sellling there didn't I? There are all kinds of different combinations for getting the speed you want. The guys above have given some good advice. Good luck with it. If you go with the procharger kit they will tell you that you can use the stock injectors with higher fuel pressure provided by a boost referenced fuel pressure regulator. A lot of guys end up ditching this to use bigger injectors and get professional help reprogramming the ECU. This really is the correct way to do it and adds to the true cost of the kit.