Power Tips For a 454 MPI

[arnienobles]

Okay guys, I have been reading alot of these forums. Sounds like you all have a wealth of information and experiance. What tricks can I do to increase power without pulling the engine? Also, is there alot of advantages to the shortened IMCO drive (Bravo 1)? Thanks guys

[arnienobles]

Okay guys, I have been reading alot of these forums. Sounds like you all have a wealth of information and experiance. What tricks can I do to increase power without pulling the engine? Also, is there alot of advantages to the shortened IMCO drive (Bravo 1)? Thanks guys

[JUPITER PULSARE]

ALOT WILL DEPEND UPON IF YOUR 454 HAS CAST COMPONENTS OR FORGED. IF YOU HAVE A 454 MAG (365HP) THE CRANK, RODS, ETC ARE FORGED AND ALOT CAN BE DONE TO INCREASE HP. THE 454 MPI (330HP) CAN EXCEPT MILD MODIFICATION AS IN EXTERNAL BOLT ONS (EXHAUST, IGNITION, ETC.) AS FAR AS THE SHORTENED DRIVE, THAT DEPENDS UPON YOUR EXISTING X-DIMENSION. IF YOUR X IS LOW ON THE TRANSOM, YOU MAY GAIN SPEED BY GOING WITH A SHORTENED DRIVE(LESS DRAG IN THE WATER).

[arnienobles]

Mine is a 454 Mag (385 HP). As far as the X-Diminsion. Are there magic numbers and how do I measure this. The boat is a Convinsor 242.

[vinny p.]

You didn't specify the year of the motor. But, being that you said it is a 454 Magnum 385 hp, I will guess that it is an MPI motor. If this is the case, you are very limited as to what you can do to that motor to gain power. I feel your pain, I have the same problem. I have done all the bolt all performance enhancements you can think of. All the while gaining very little top end. No more than a couple of MPH. I knew going in to this, that I would net a very small gain, but I wanted to do it anyway. First off, being that I HATE factory Mercruiser exhaust manifolds and their ridiculous leaking risers and gaskets, I changed over to Gils Wet Offshore manifolds and pipes. It looks and sounds a whole lot better, but I saw next to nothing on the speedo. I added MSD6M-2 ignition box, not because it would make it go faster, but because it cleaned up the sooty transom. I added a Teague billet flame arrestor and adjustable fuel pressure regulator as well. And of course, saw next to nothing on the speedo.
The bottom line is this. We can not modify these motors to make any noticable increase in power unless you get into re-mapping the ECU. After hearing several horror stories from well known companies that do this re-mapping, I will NEVER chance my well thought out and built motor to some idiot across the country who thinks he can get my fuel curve right, just by talking to me on the phone a couple of times. I talked to them once, I am still laughing at what they told me.
My answer to this problem is adding a Whipple. I also believe that a Whipple is not just to be " bolted on the stock motor " as they claim it to be. You really should at least get Inconel valves and Cometic head gaskets. They are just going to fail anyway.
If a supercharger isn't the way you want to go, then get rid of the MPI and bolt on a carb. Then you can do what ever you want to the motor and tune it yourself.. However, you still have to get rid of the stock Merc exhaust to prevent reversion with the new cam profile you want to run.

[boatn70]

excellent info vinny, offshoreonly also has alot of threads on the subject.
arnienobles, what kind of speeds are you seeing with your 242, ive got a 98 with the low hp carb motor and see 57 mph, just wonder what to expect with a mag motor, or at least the equivalent hp as your 385.
kevin

[arnienobles]

Thank you for the information Vinny, I was afraid this was going to be the case. A blower might be in the works next year then. I do not want to give up the fuel injection because of the reliability. The boat is a 96 242 convinsor with a bravo 1 drive. Completely stock. This is my first checkmate. So far I love it. Keven, according to the unreliable speedo, my top end is 64. If weather is permitting this weekend which it probably will not here in Green Bay, WI. (Weather really blows here!) I will GPS it. Vinny, do you know very much about the Pro-Charger system? This will allow me to continue to use my fuel injection.

[vinny p.]

I have no first hand experience with any type of chargers. But, I am in the market for one myself as a winter project. If I do go with a charger, it will be a Whipple. I have heard that prochargers tech line is not good. In fact, it sucks!! While whipples is excellant. I have been researching the 2 systems for a while now. I have not heard 1 bad thing about Whipple, while I have heard several bad about ProChargers. Besides the fact the Whipple looks much neater when installed. I don't want to see all the plumbing for the air that a Pro Charger needs. Some one I know,( not a close friend) had a Pro Charged HP500EFI. It ran fast, but it was never right. Even after a few attempts at sending the ECU back to re-map, it was always either lean or rich. Eventually, he took it off and went with a roots style charger and carb. Problem solved.
By the way, I won't give up the EFI system either!

[arnienobles]

I did'nt realize that Whipples could be run with MPI systems. This is good news since it was the only reason I was looking at Pro-Chargers. I am glad you gave me the low down on them. The last thing I want is problems. I only get approximately 3 months of boating here in Green Bay so I don't have alot of water test time verses enjoyment time. I want the enjoyment time. I do wish there were other things I could do to it besides blowing it. All I want is to get in the 70 MPH range. A honest 70 MPH range. Vinny, thank you for your help. I swear, this is the best website to be with.

[vinny p.]

Check out this link..

http://www.whipplesuperchargers.com/product.asp?ProdID=1148

[vinny p.]

That speed sounds a little low for the boat. I get more than that with a basically stock 454 Magnum pushing a 259 Convincor. What prop are you currently running? What pitch?? What r.p.m. are you turning? What drive ratio? Most likely a 1.5???

[JUPITER PULSARE]

HEY GUYS, LOTS OF GOOD ACCURATE INFO ON THIS THREAD!! THE ORIGINAL 454 MAG CARB WAS RATED AT 365 HP. IT WAS A GREAT BASE ENGINE FOR MODIFICATION. YOUR MPI UNITS ARE WELL THOUGHT OUT BY MERCRUISER BUT AGAIN, LIMITED IN WHAT CAN BE DONE TO ENHANCE PERFORMANCE. BOTH WHIPPLE AND PRO-CHARGER ARE GOOD UNITS. THE WHIPPLE DOES LOOK ALOT BETTER THAN THE PROCHARGER. IF INSTALLED CORRECTLY, THE PROCHARGER IS A GREAT UNIT AND HITS HARD. THEY HAVE DIFFERENT PRICING ON THE PROCHARGER DEPENDING UPON HOW POLISHED YOU WANT THE SUPERCHARGER TO LOOK AND WHAT SIZE KIT. IN EITHER CASE, DO YOUR HOMEWORK AND TAKE YOUR TIME. I HAVE SEEN NUMEROUS PROCHARGER INSTALLATIONS AND THE LITTLEST THING SUCH AS CARB JETTING ON THE HP500 COULD BE ALL THE DIFFERENCE IN THE WORLD ON THE PERFORMANCE OUTCOME OF THE MODIFICATION.

[arnienobles]

I did not get out this weekend to GPS my boat. It rained heavy all three days. Bummer. Vinny, I don't want to tell you anything wrong when you asked that stats on my boat. I am running a 25P Mirage Prop. Don't know what the diameter is. As soon as I get it back on the water, I will let you guys know what speed and RPMs I am running. I think you put the fear in me about remapping my computer. When I was in the Whipple website. They stated that they will remap my computer. Is this just as dangerous verses trying to find a shop around here to do it once the blower is on?

[vinny p.]

If you go with the Whipple, you must absolutely have them re-map the ECU for you. Dustin knows what he is doing with his system. He is the best qualified to get it right. That is the good thing about adding a Whipple to a stock motor. The homework for doing the re-map has already been done. Whipple has set the program up right there at their location on a stock motor just like yours and mine numerous times. So, providing that you don't change anything that would effect the fuel curve, it will work right the first time for you.

Post those numbers when you can get them.