Whipples on 6.2 MPIs & Bravo One
 

I'm very close to pulling out the credit card and buying a pair of Wihpple SCs for my 2003 Formula 292, and have afew questions for anyone with insight on this topic:

Right now the twin SB motors have 190 hours on them. Whipple says with mild boost (I'm thinking no more than 5-6 lbs.) and the addition of oil coolers, I should be able to get 500 hours out of the engines before tear down is required. Also said that the stock manifolds with thru-transom exhaust will be sufficient, not alot of gain to be had with aftermarket exhaust such as the CMI E-Tops, etc.(I said huh?).

I'm targeting 450 HP per side, up from the stock 320. Running stock Bravo One drives with the 1.65 gear ratio. Boat weighs about 7000 lbs. dry

Questions:

-Are the above expections for power and longevity reasonable, assuming correct maintenance (and no abuse)?

-Has anyone on the board Whipple'd a 6.2 MPI? Are there weak points anywhere in the internals that needed replacement either during install or soon after?

-Will the stock Bravo One be an issue? What about the gear ratio of 1.65, will I need to move down?

-I think I can Whipple both engines for a total of about $15,000, add another $6-8k if I need exhaust. Have no idea what gear changes in the drives would cost if I need them. If I grenade one or both of the B1s, things start getting really expensive, and the boat stays dry for a while.

-The really big question: I like my 292 for a lot of reasons, but wonder if I may not be putting too much time and money into trying to make this a 90 MPH boat, which could end up being potentially unreliable and without a lot of resale value. Has anyone else gone down this path and ended up wishing they'd just moved into a bigger boat with big block power and XR or better drives?

Thanks.

I believe that SPECTRAS ONLY has the same set up that you're looking to do. I'm sure that he can give some advice on the topic. The Bravos should hold up well. Even though you are going to make some good power, tha bravo will handle the amount of torque the small blocks will make. A good exhaust will always help a blower motor, but you may get away with stainless CMI tops with a through hull set up.


Darrell.

:I was going to do the same to my boat when I had the 6.2's. Got talked out of it by many people. Sold 6.2's and bought a set of blower motors. :cool-smiley-011: Best thing I could have ever done. You should be able to get decent $ for the small blocks. Went from 70mph to 90mph. You will most likely have to change gears if you get close to the 500hp range.
Jamie

Take the small blocks out, you can buy a set of used 496HO for aprox $20 000.00 (there is a set in the classifieds now) . Run them with your Bravos. Should have no issued with the drives. Relativly small boat for two bravo's to push, they won't be working hard. Then if when you sell, throw the small blocks back in, or sell the small blocks to help pay for the 496's.

Just idea. Don't get me wrong, I love my Whipple, but for the hp your looking for, I'd give some big blocks some thought.

If you do it the bravos should be fine....BBC putting out 500HP run with regular bravos regularly. You'll probably go from 28 to 32 pitch props if you keep the same gear ratio......not ideal, but acceptable. Swapping to BBC motors would be the easiest/cheapest but can you stuff them in there? That boat was built for SBC and may not be spaced properly for BBC. Also, your boat barely hits 70....the addl. HP will get you past 80 but probably nowhere near 90. and with any upgrade....if your going to keep the boat for 3-4 years or more then do it, if not.....then don't.

Formula has never offered big blocks in the 292, and it would be a very tight squeeze - Not alot of room to work in the bilge as is, so in that hull it is going to have to stay mouse-motor powered.

As for top-end once Whippled...I wish I had a crystal ball on that one! Mid-80s would be acceptable, but 90 is what I'm shooting for.

Your boat is 8 ft 3 inches wide just like mine.......I have (2) 540's stuffed in there, don't tell me about tight!!!! :D As for speed predictions...I added about 130HP per side and gained 10 mph over the stock set-up. Whipples would add about 130 it appears which should be about 10 mph in my book. SBC can be done, but will have to be built from the bottom up and VERY STRONG to get your boat to 90 (just my $.02). Adding 5+ lbs of boost to a stock motor WILL cause you to build a better bottom end sooner vs. later.

Hmmm...I really like the V-Bottom for those rough days in SF Bay or when I'm outside the Golden Gate, but if I want speed for (relatively) cheap, I may have to go cat...

I did a search for SPRETA ONLY to send him a PM but the search function came up with nada. Hopefully he'll see this and respond to relate his experience with SCing the twin 6.2 setup.

Rob:
Be careful with this idea. The 6.2's have been troublesome when they are stock and naturally aspired. A forced induction set-up could easily push them over the edge very soon. I wasn't aware Formula never offered the 292 with big block power. That could be inaccurate.
With the additional horsepower you can go to a 1.50:1 ratio and have a better propeller selection. Make sure your Bravos have the latest gear sets available from MerCruiser. Good luck.

I understand that the 292 twin stepped hull was designed specifically for the weight of small block. Putting big blocks in there would move the CG back and be ass heavy. Remember, it really has only around 27 feet of running surface...

I think you should go for it!!:D (for selfish reasons...) I just want to hear how it works out!:p

It is my understanding that the exhaust on these 6.2's is not very good. The exhaust ports just dump into a chamber close to the block so you get 'interference' from one cylinder to the next. Tubed headers or manifolds scavange much better, especially if you are talking a blown engine.

Regarding gear ratio, everything I have read is you are much better off going with a taller prop than, say, dropping to a 1.5 ratio. In this case you have several options over 28" pitch. I would go 5-blade as well...

I have been going through the same thought process you are and decided to keep running the 6.2's for several years then build engines from scratch. Mainly for reliability.

We spent a LOT of time researching and comparing before purchasing the 292. It really fits our needs perfectly and we are keeping it for the long haul. I used to have a cat. Insurance is high. Cats tend to not have as much storage. Overnighting is not an option unless you go really big. The ride can be wet in rough water, again, unless it is really big.

I guess I would be wary of supercharging a stock 6.2. It only holds 4.5 quarts of oil, no wonder they recommend a oil cooler.:rolleyes: That would have me concerned. Not sure the fuel system would be up to task either and that is critical, especially with stock internals...

What ever you decide, good luck!!:ernaehrung004:

Don't mean to hijack, but could you elaborate a little drippin? Was this a 292 you had? How did it handle at 90mph? Thanks!

Hello look in the formula section there are several post's on this. I was looking to do the same to a friend of mine 292 and from everything i read and heard the small blocks had to be redone and bulletproof which wasn't cheap. Pull the small blocks and go with the big block much cheaper and easier.

Put a couple of big blocks in a 292? That is a bunch of weight for that size boat. I too have heard of problems with the 6.2. Most of those have been when they used then as a replacement for 454's in heavy boats. Although the hp may be the same, there are a few other variables involved with pushing a heavy boat with small blocks. I know of plenty of folks running lighter boats hard with the 6.2's with no problems.

I would probably throw the blowers on the 6.2's with low boost. I think that 500 hours might be a stretch but heck you may get lucky. Then you could freshen them with heavy stuff, crank up the boost and have a screaming boat that handles well.

I too have selfish reasons for saying that. I have that combo in my little Donzi X-18. It is a great package for that boat. With the shorty I am putting on I will get 75+ with a stocker. That will do for a while, then it will be time to add boost. I am curious how it will work out.

http://www.gmhorsepower.com/ZZ_383.html
Just a thought, if you have some marine cams ground up and have an engine shop set up an induction / ignition package on a dyno.
Keep the 6.2's stock for when you sell...It's hard to find a buyer who likes custom engines.

Bolting on a supercharger without a dyno is risky. You have no way of setting the compter up perfectly. All you can do is pull plugs and test run, pull plugs and test run. Not a great way of tuning it. I went through this this summer. My engine is now getting tuned properly on a dyno, and have found both rich and lean conditions at different rpms. We will have Dustin recalibrate the computers so the engine is running perfectly at all rpms. Far less risk of damaging the engine.

Just giving you some experienced information. Whipple can recalibrate your computer to work, but every engine is different. Just FYI

No,It's a PQ 300 Revenge. I ran out of prop with the 1.65 gears and had to go with the 1.5"s It handles real well at 90,heavy deep V.

I installed a whipple on a 6.2 for a customer 3 years ago. It was in a 20' Cobalt. It ran great for 2 years until this summer, when he broke a piston. I rebuilt it with forged pistons and added aluminum heads. It made 590 HP on the dyno. He is running a Bravo with 1.65 gears. He likes the hole shot and is constantly making full throttle starts.

I would recommend staying with small blocks in your boat. Install the Whipples and make sure water pressure is good and always have good fuel. The pistons are the only weak link in that engine. So, be aware you may have a failure or pull the engines and replace them from the beginning. Whipple does a good job on their programming right out of the box, but it is certainly better if you can install an 02 sensor and get it perfect. As long as the tune up is good the pistons will hold up, however forged pistons will buy you a little insurance if something goes awry.

Bob

Nice!! That PQ hull with twin steps looks a lot like the 292. I know our 292 at 70mph sure feels secure, like it can take on a lot more HP and speed.

IMHO I have to disagree with you guys recommending big blocks... Swapping to big blocks will put an additional 400+lbs on the ass end of the boat throwing the balance way off. I know I wouldn't want to mess with that. My 292 flys straight and level as it is.

You would be surprised how much reliable horsepower you can get from a 'properly prepared' big inch small block. That, along with the lighter weight (especially with aluminum heads, intake, headers, etc..), may surprise many larger twin big block boats in acceleration, handling and top speed. Plus you actually have room to work on them!!:cool-smiley-011: