Blower on "Pleasure Boat"

[H2O]

Hello,
I have a question about putting a blower (Whipple or Procharger) on my stock 7.4/300hp carburated Mercruiser. I am only looking for modest power gains (say 40%) and I would keep it within stock RPM limits, since the motor has cast pistons, 2 bolt mains, etc.
My question is this: When I prop-up, to take advantage of the extra HP on top, will the boat be a dog out of the hole?
At what RPM do these kits start to make boost? (assuming I'm pulley'd for 5 psi) Is this is good choice for an "all around boat" where I still want to do a little skiing and maintain decent cruising MPG and reliability.
Thanks to all!!!

[djunkie]

I'd say 40% is quite a bit more than modest. :D

[VDRIVERACING]

IMPORTANT - Outdrives are really expensive. Remember that your outdrive was spec'd for the torque output of your current engine. Depending on your increase in power (don't count on 40% more), you may only need to upgrade a bearing set, or shaft, or you may find out your unit will not handle the extra torque at all. But researching this aspect is a must before you spend a dime on your powerplant.
To answer your question, most superchargers will increase your low end power. A roots-style blower, like the Whipple screw drive, will provide you with power right off idle, whereas some of the centrifugal units will have some lag, but probably hardly noticable in your application.
My impression is that you have a stock boat, and want more power without a complete make-over. I have heard a lot of good things about the centrifugal units lately, and they fit neatly under your current engine cover. I suggest you call the competing manufacturers, and get some specs and price trade-offs. Also ask them about materials, warrenty, life expectancy, and what other components need to be upgraded/changed.

[ghittner]

Good advice above. I've been running the same Bravo One drive unit since 1989 and have serviced it yearly. I have done no upgrades and it has lasted through three 454's, 1-330HP, 1-500hp, 1-650hp and now I've blown a 498 @ 800 or so HP with a season 50 Hours or so, on the same drive, no work on it yet. Be nice to the drive, it's not a drag car or a stump puller and it will last you a very long time. I currently and in the past run my set ups at up to 6800 RPM for extended periods. Hope that helps.

[H2O]

Thanks guys, good stuff so far.
I have called around to the manufactures and dealers and discussed their products. Of course I take that with a grain of salt, since they are all trying to sell you something. I am especially interested in what real world users have found in the day to day operation of their boats.
I was under the impression that a Bravo One could handle 400 + horsepower if treated gently, as ghittner seems to confirm. While I admit that 40% is not a modest power gain in general, it is modest compared to what the maunufactures are claiming on this engine.
http://www.procharger.com/M_engine.shtml
Procharger is showing 465-525 hp on a stock carburated 7.4 and I was saying I would be happpy with 400 to 425. (Partly becuase I don't believe everything I read and partly beacause I don't want to break anything).
Thanks again, keep the good info coming...

[DMOORE]

Like the guys above have stated, a lot of how reliable these systems are( for the motor and drive) is how they are used. If you do not go too crazy with the boost, your motor can easily handle a supercharger. The bravo drives will handle the power as well. Just remember, no WOT hole shots. Roll on the power when coming on plane, and roll off when coming off plane. As far as when the boost comes on, all supercharger types and systems are a bit different. I have a roots type blower on my motors that make 10PSI. At a cruise speed of 3500RPM my motors are still pulling vacume ,and live a very easy life. The prop is yet another part of the puzzle. You should be able to find a nice prop that will still alloy a good planing time, and give you some good top end. A lot of the boats that I have seen that went the same mild supercharger route you are looking at, have seen roughly a 10-15MPH increase.
Darrell.

[VDRIVERACING]

A lot of good info from these guys.
I have never, ever, heard somone regret the addition of a supercharger. Installed properly, and operated with good judgment, your motor should remain reliable and smooth operating.
As a matter of fact, you're ahead of the game by starting with a lower performance motor, because the cam will be better suited for a blower, than a HP cam for a carbureted motor would. The biggest difference from your cam and a blower specific cam, would be a longer exhaust duration.
One final thought: make sure your crankcase ventilation is in good order, and increase your oil change interval. I don't know how fresh your rings are, but by their nature, blowers tend to drive more intake charge past the rings during boost. A small price for what should feel like a new engine.

[Infomaniac]

Not to be a spoil sport or anything ..... but you have the worst engine to bolt a supercharger onto. It works great as designed but does not take well to the extra power. An additional 40% in my opinion would be too much to live very long.
Great input from everyone.

[franky]

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.

[ghittner]

Just a thought here.... I too was nervous about the blow through set up. So much so that I went with a roots style B&M 420 even though I had to raise my hatch 5". From the day I started it until now, it has been very simple, straight forward and tuning is a breeze as the carbs are working as they were intended, drawn through. no problems to date whatsoever..........And, it looks really bitc$#n when you open the hatch...

[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:eek: Of course the stock fuel pump and 3/8 lines arent going to feed a blower and 1250 carb:eek:
_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:eek: Of course the stock fuel pump and 3/8 lines arent going to feed a blower and 1250 carb:eek:
_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:(
:D LMAO:D

[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.........

[TIMINATOR]

You can take your info from someone who has done one or two installs and has gotten lucky,or doesn't have the experience to know what to expect, or from the peeps that do it for a living, and have for over 30 years, not just me. There is a lot of experience here, it is up to you to figure out who has the most of what you need. The most important thing that you need to remember is that if the"cheap way" fails, only YOU will be paying to redo it. You will hear a lot of "gee mine didn't do that", but no offers of financial aid. People in the business have a reputation to protect, and want happy customers. The most important info you need here is: "get by with, and blower" should never be used in the same sentence. Call me and I will explain cams,theory, and a bit of knowlege, etc. TIMINATOR

[ghittner]

If you are not going to build it yourself, listen to the the builder, do what he says exactly and then if things go awry you will have a leg to stand on when it's warranty time (hopefully not). Just be aware in this business of the many out there trying to oversell you and that think that there are unlimited funds from the boating customer. AND....Many are not. Also many that claim they can do the job for you who are not experienced or qualified enough. Go to a shop that you know, or that more than one person has recommended for the type of HIPO install and tuning you are looking for. You are looking for turnkey reliability above all. Find one that has a good reputation and is NEAR YOU. Talk with the customers (not just one) that have had your particular mods done, a good shop will provide plenty of those names for you. Some of them should have had some type of issue that has been resolved, not all jobs are in Cherry Land so don't let them tell you they have never had a problem or a comeback, that's B.S. Mainly, learn from the builder so that you can attain the knowledge you need to hear or spot a problem or better yet, next time, do it yourself. Timinator has given lots of good advice here in the past to me and others and has been free with it, he is a good source. There is more than one way to build a particular set up, and more than one opinion, thank God, I've changed my builds more than once with some good advice. I choose the simplest way that insures 1) The most reliability. 2) Easiest and most common parts to replace for the least cost to acheive the results desired. 3) The simplest way to get there. 4) The lesser number of oddball parts you add to a system the better. The less parts in total for something to go wrong with, for sure the better.

[VDRIVERACING]

The most important info you need here is: "get by with, and blower" should never be used in the same sentence. Call me and I will explain cams,theory, and a bit of knowlege, etc. TIMINATOR
You nailed it.