Supercharging Mercruiser 4.3MPI

[msswany]

I have a 2007 Tahoe Q7i with a 4.3MPI, I ordered the boat new in the fall of 2006 and talked myself into the 4.3MPI over the 5.0 or 5.7MPI's because gas was getting more expensive then... haha... well now that spendy gas is just the normal I thought about repowering with a 5.7MPI, but the cost just didn't seem worth it. I started researching supercharging the 4.3... and was pretty much told it wasn't worth it or it wouldn't work. Well, maybe that is what inspired me to complete the project and make it work. I now have a supercharged 4.3MPI putting out by working some numbers in the 300 to 320hp range with only about a $2500 investment. I have attached a picture of the completed project.

 

[haulnazz15]

Re: Supercharging Mercruiser 4.3MPI

Well, nothing wrong with that, but I don't see how that's cheaper than getting a 5.7L and bolting most all of your 4.3L components to it. Either way, congrats on the new power adder! I bet you'll get out of the hole a good bit quicker for sure, lol, but I'd be easy on that Alpha I (especially out of the hole) as it is only rated for 300HP max.

 

[aerobat]

Re: Supercharging Mercruiser 4.3MPI

thats very cool ! how did you convinced the electronics to give more fuel into the charged engine ?

 

[Bondo]

Re: Supercharging Mercruiser 4.3MPI

thats very cool ! how did you convinced the electronics to give more fuel into the charged engine ?

Ayuh,... Ditto,... Cool motor,... How'd ya fix the software,..??

 

[msswany]

Re: Supercharging Mercruiser 4.3MPI

As for the Alpha I only rated for 300hp... I'm not too worried... If the 5.7 is 300hp, 20 extra isn't gonna hurt it. There are a few guys out there push 400hp+ to an alpha without a problem and about the only thing off the 4.3 I could bolt on for externals would be the throttle body... everything else is different on a 5.7, and to get a complete 5.7MPI new would be about $7-$8,000. As for the motor I didn't do any updates to the software, I used and FMU(Fuel Management Unit) which tricks the fuel pressure regulator into delivering more fuel, It isn't the most accurate way, but it works and what most out of the box kits use. The main part of the kit was for a 4.3 Chevy blazer/S-10. I had to modify the bracket and move the supercharger over 2in to make clearance for the coolant hoses, notch out the back mounting plate to fit the longer alternator and a few silicone hoses and adapters to get it all to fit correctly. Other than that it pretty much bolted on.

 

[emilsr]

Re: Supercharging Mercruiser 4.3MPI

Clean install. How many PSI of boost are you running?

Doesn't look like a USCG approved spark arrestor (more like a K&N filter). You'll want to fix that before the coasties see it.

 

[rowlex]

I want to see the video!!!!!!!!!!

 

[QC]

Re: Supercharging Mercruiser 4.3MPI

Pretty impressive, and other than the spark arrestor issue, seems legal even. We gonna see some results?

 

[aerobat]

Re: Supercharging Mercruiser 4.3MPI

impressive work , you have an unique engine !

 

[carey965]

Re: Supercharging Mercruiser 4.3MPI

nice a centrifugal blower, for some reason i was expecting to see a roots type sitting on the top

i am wondering with the blower between the filter and the carb and it all being sealed up he may not need the spark arrestor
but either way the blower whine will make you the envy of the lake, i think i see a winter project for me

 

[QC]

Re: Supercharging Mercruiser 4.3MPI

I am thinking legally he still needs the SA regardless of whether or not it does anything productive.

 

[Fun Times]

Re: Supercharging Mercruiser 4.3MPI

K&N makes flame arrestors that satisfy Coast Guard regulations and offer critical engine protection.

K&N Marine High Performance Flame Arrestors / Air Filters

 

[PS94]

Re: Supercharging Mercruiser 4.3MPI

We need more details of this build!!!!!

 

[msswany]

Re: Supercharging Mercruiser 4.3MPI

That is a K&N Spark Arrestor, Part# K&N 59-5003. I can take more photos of how I did the build. I will have it on the lake tomorrow night and can take some video of her running. It actually sounds pretty mean with the supercharger whine. I also have corsa captains call exhaust on it coming straight out under the swim deck, sounds like a v8 at idle... you get a little bit of a prop air plane sound out of the v6 after that. Now I get to play the prop game again. I have had 5 different props on it trying to get the power band just right prior to the supercharger. Right now I have a 21 degree Merc High 5 on it, I also have a 20 degree X7 enertia. The high 5 was a bit better out of the hole and I was getting between 50 and 55mph out of it. with the X7 I was at about 58mph at 4800rpm but would run out of HP. so I might have to step it up to a 23 degree now.

 

[emilsr]

Re: Supercharging Mercruiser 4.3MPI

That is a K&N Spark Arrestor, Part# K&N 59-5003. I can take more photos of how I did the build

Please do, and share some of the details. Hardly anyone, actually nobody that I have seen, has done much with the 4.3.....and I don't really know why as they've made proven power many times in automotive applications. Same power as a 350MAG and several hundred pounds lighter should make for a good running boat.

I bet a lot of folks are following this thread.....

 

[Tail_Gunner]

Re: Supercharging Mercruiser 4.3MPI

Looks good from here...Is it a wynjammer??

If you give these guys a call... they do have a work around for that merc software you have there, actually i would really give them a call running a super charger with a fuel regulator is crazy...But that's just a opinoin...Or call Bob at mefiburn and get his input..he does this kind of thing on a much larger scale and he will tell you you have some crazy fuel and timing curves already plugged into that 555.

http://mefituning.com/

 

[carey965]

Re: Supercharging Mercruiser 4.3MPI

any updates? I really want to hear this thing run

 

[msswany]

Re: Supercharging Mercruiser 4.3MPI

I ran it last Friday, and then the weather got crappy so I didn't get video... But when I did run, it shot onto plane almost instantly with no hesitation and I hit 5000 rpm and still had about a 1/4 throttle left, will be switching props and ill get some video and get it on here.

 

[carey965]

Re: Supercharging Mercruiser 4.3MPI

I have been waiting patiently. Any more pics/vids or info on how she is running?

 

[NOLA-boy]

Re: Supercharging Mercruiser 4.3MPI

Wow!! Awesome! I've got a buddy with twin VP 4.3's. Wake it up big time!! Cant' wait to see some GPS, video etc......
Great post.
Thanks!