Blower on "Pleasure Boat"

[VDRIVERACING]

Same experience with the Bravo, be nice to it and it will take the power. Had a Cole with a 7.4 330hp upgraded to about 400, then 500 then added Vortech, ran like a banshee till the cast pistonn gave up (you will rape your motor too). Built it back up w/forged averything, 800 dyno hp, no problem on the Drive. Boat now has a smaller motor but same drive 13 years later.
Couple things, go with the Vortech, much nicer (refined) kit than the Procharger. Definitely have an intercooler. Vortech makes a nice carb box (I made mine) and expect to spend a lot of time getting the carb set up right to work under pressure (the whole thing). Think about this, carb in a pressurized box, 10 pounds of boost (I had 13 at 6K), so now you have 7 pounds of fuel pressure trying to overcome 10 pounds of pressure. So yeah, you boost reference the regulatar. OK now what regulator/fuel pump likes to go over 17psi? EFI reg, but they dont like to start at 7 and (ref boost) to to 17. I ended up with a Paxton (aeromotive) EFI pump feeding a (Paxton) EFI reg set to 35 (with a return) feeding a Mallory reg boost referenced. Worked great but VERY Frankenstineish.
If I had it to do over again I would have never messed with a blow through carb set-up. However, once dialed in it was turn key, idled at 600 rpm, fit under the hatch (sleeper) and ran like no tomorrow. It was fun making it work and very different. ( I made my own BIG intercooler using Spearco cores)
So with all that said I would say if you are set on carbs and a blower, Whipple and the Bravoo will last if you don't punch it out of the hole, roll it on plane then get after it. Don't get air and then romp it on the landing, blah, blah, blah.
Reason #999 to ask a lot of questions. It's rarely a matter of "bolting on" 100 HP or so, on the other hand, it's not like Vortech hasn't done this before. My bet is they have all the knowledge, and parts on the shelf, to make this work without the consumer needing a bridgeport mill in their garage.
I have an 8-71 blower with carbs on top, and they are really simple, and might even be cheaper. None of this is a do-it-yourself job for the first timer, but is a common job that a performance boat mechanic can handle. The B&M kits make it even easier.
You've taken the steps to decide if your boat can handle this. It can. Now comes the truely agonizing part. Find a shop you can trust to install and tune whatever system you have chosen, and brace yourself when you ask what the "total" turnkey cost will be.

[H2O]

Very productive thread here folks, thanks so much.
Dmoore - You answered another question I had, which was how much boost at cruise. Good to know the motor would be living an easy life at that RPM. I always amazed how seldom I make boost when cruising around in my buggy and watching the boost gadge. Granted that's a turbo and has MUCH less load that a boat, but it's interesting to note you still pulling a vacuum in your boat at 3500.
Can anyone recommend a good dealer/tech for Whipple, Vortech, or Procharger?

[gmocnik]

Can anyone recommend a good dealer/tech for Whipple or Vortech?
everyone will have their own opinions and experience regarding this question. I have used whipple systems for the past three motors, a 2.3 carbed setup, a 2.3 efi, and the current 1000hp quad efi. GT Performance has done all my motor work and these motors have been turn key "pleasure boat" motors. Gary does a lot of work with Whipple and has a lot of experience installing and tuning. There are only a hand full of efi tuners out there who can setup these systems to run correctly. I also have first hand experience with Pfaff built whipple motors and they also build a reliable system.
Good advice on the drives...I had Max Machine do all their stuff to mine and have not had one let loose yet...I know it is coming but I do the annual PM to prevent the mid season explosion...
good luck...hp is addictive..

[TIMINATOR]

A well designed, properly applied roots or whipple type blower will allow a bigger pitch prop to be used because the boost is linear. That is if it makes 6 lbs at 5000 rpm, it will make the same boost at 2500 rpm (at full throttle), and that will allow more torque to get on plane with the bigger prop. Centrifugal blowers will create 4 times the boost at double the rpm. 6 lbs at 5000 equals 1.5 lbs at 2500 rpm, much harder to get on plane. So typically you must run a smaller prop and have a higher cruise and top end rpm because of this with the centrifugal blower. A whipple or roots makes more bottom end and allows a much larger pitch prop to get on plane, and that will lower the cruise and top end rpm. and rpm is not your friend with cast pistons. The lower cruise rpm uses less fuel and makes less noise. My Daytona picked up about 20-25% in mileage with the addition of the 14-71. Nobody believes that until they ride in it. Cruise rpm is now about 3000 rpm at 60 mph. I can pull a 30 or 31 pitch 4 or 5 blade prop too with a 1.24 drive. The fuel mileage gains were not totally realized until I boost referenced the powervalves. See ***boat (the magazine) from about 6 months ago. The stock cam is not suitable for reasonable power gains, and the valvesprings will need to be replaced for a cam change too. To do this properly it won't be just a bolt on as you have been led to believe. We do blower installations, and boost reference quite a few carbs,everybody has been happy with the results. Many peeps have just bolted on blowers and had mixed results, and problems. We make a good living out of fixing their mistakes. I can post pics, LOTS of pics. TIMINATOR

[396_WAYS_TO_SPIT]

Dont forget fuel management!!! My friend bolted a blowershop blower on his 502 and it leans out at WOT Of course the stock fuel pump and 3/8 lines arent going to feed a blower and 1250 carb
_Spitter

[H2O]

TIMINATOR - Thanks for the well thought out reply.
I heard that screw type blowers make their boost at lower RPM's than centrifugals, and regarding coming on plane this is exactly what I am looking for. Given the limitations of my engine howerever, is that all good? Would you want more torque, power and heat in a high load, low rpm situation (i.e coming out of the hole) in terms of engine durability?
Without giving away any trade secrets, what aspect of the cam needs to be changed? I was under the impresions that low boost applications do well with low compression and mild cams. For installions like a stock Merc 7.4 with 5 lbs of boost, do you dyno tune every motor or is the timing and jetting generic enough that you know where to start with a "base map". (not really a map I know)
Thanks again, I really appreciate it!

[VDRIVERACING]

Dont forget fuel management!!! My friend bolted a blowershop blower on his 502 and it leans out at WOT Of course the stock fuel pump and 3/8 lines arent going to feed a blower and 1250 carb
_Spitter
Good point. This is another place where you get the checkbook out again. Carbs should be set up for blowers in a variety of ways, and a boost reference circuit is a must, IMHO, to maintain the correct mixture between boost and non-boost. I fouled a lot of plugs before I learned of this. A bit of overkill on the fuel "supply" is also a good idea. That sucker is gonna get hungry quick once you transition into boost.
Regarding boost and how much and when it kicks in is a function of the blowers ability to receive air (the size of the venturies), and the pulley speed of the blower. There's also what I'll call false boost. Your boost gauge may be soaring, but unless that discharge has a clear path to the cylinders (via cam design and head specs), it's just pressurizing the intake manifold. I had 750's and only made boost when I had my foot deep into it. I then bolted on 1150's, and was making boost with just moderate pedal. In other words, the blower now had an ample supply of air.
Timinator was dead on about the cam. Blower cams understand that air/fuel is being forced in and avoids much overlap ( otherwise unburnt charge slips into the exhaust manifold where it burns and increases exhaust temps), and since there's a lot of burnt charge(now that it's "decompressed") the cam needs more duration on the exhaust. Cams are relatively cheap, and will really make a difference in the torque department with a blower.
Now, let's see. You started with a "simple" bolt on project to wake up your cruiser, and now the shopping cart includes, cam, springs, carburetor work, fuel pump(perhaps) and bigger lines, a professional installation and tune, blower of your choice. We haven't got to intercoolers yet...

[H2O]

Now, let's see. You started with a "simple" bolt on project to wake up your cruiser, and now the shopping cart includes, cam, springs, carburetor work, fuel pump(perhaps) and bigger lines, a professional installation and tune, blower of your choice. We haven't got to intercoolers yet...
Isn't that always the way!!!??? "Let's see, I went out shopping for a $500 pocket bike at Pep Boys and after "conducting the appropriate research" I can home with a twin turbo Hyabusa that turns low 9's in the quarter..." Sorry honey

[Deano]

Isn't that always the way!!!??? "Let's see, I went out shopping for a $500 pocket bike at Pep Boys and after "conducting the appropriate research" I can home with a twin turbo Hyabusa that turns low 9's in the quarter..." Sorry honey
LMAO

[ghittner]

Don't get overly caught up in the boost referenced carbs. I did and found out that I didn't need them in the first place. I spent hours and hours and hours talking with people and researching on my own as to whether or not they are needed. Bottom line was that if you run your boat @ WOT and your vacuum is less than the power valve rating, you are providing all the fuel on the main metering circuit. You can do this the first time out while tuning in your new setup just by watching your boost gauge. I'm running a B&M 420on a 498 C.I with normal 750 DP's and #50 power valve. Mine runs zero (0) vacuum @ WOT 6500 RPM with 8 pds boost so all was well for my setup with the carbs working exactly as intended straight from Holley. I did not have to mess with a thing other than jet tuning, it idles clean, runs clean and smooth with plenty of color on the plugs, and makes about 800HP. Run the carbs first and make sure they are not leaning the motor out by watching your vacuum @ W.O.T. Change your jetting as required with a plug read. THEN, ONLY IF NEEDED, spend the extra to have them boost referenced or do them yourself. It is an easy mod, the problem is everyone that does carbs will tell you it's a "black magic" dealio....PS, I do it on a mechanical Carter racing fuel pump that flows 175 GPH, runs 8 Pds. all the time, requires no fuel regulator, costs 130.00 and flows enough for over 1000 HP. Remember, K.I.S.S. Just my opinion.........