carbureted to MP Injection conversion ?

So i have '01 Indmar 5.7 carbureted, and have been trying to figure out the pros, cons, and feasibility of converting my engine to a MPI intake. My motor runs quite well now, its just i've had some carburetor problems lately and just wondering. I have about 310hp, and we all know a little more never hurts when your trying to drag 2900# of ballast out of the hole.

From what I can gather its a costly and trouble-some change over. Disregarding the marine aspect for a second. Simply introducing an MPI intake system to what was carbureted, you have to consider cam, compression, port size and shape, etc, etc.

And apparently when introduced into a marine scenario there is even less room to play with. Since Indmar applies bigger stronger cams to their motors you pretty much have to use the Indmar computer (or at least their config).

So for no lets than $2k (doing the work yourself). What do you get (assuming you do it correct)? More reliability, longer engine life, more horse power?

Is this correct? Has anyone done a conversion, with or without success? Is it worth the money?

If anyone has done it or have any pro knowledge in this area i'd love to hear from you.

Ben,
I was wondering the same thing except for a 4.3 Mercruiser lol...I know, no power to begin with and small engine. Should have sprung for the MPI then, but it was 4k I didnt see as justifiable. Good luck if you do it and I'm curious to know if others have done the conversion for either engines..

I would spring for EFI every time given the choice, but IMO it's not worth the hassle & cost to do a conversion. Throw a new carb on it and a lower pitch prop. There is nothing wrong with a properly tuned carb.

I haven't done the conversion, but seems you would be better off getting a whole new engine that is MPI if and when the time comes for a rebuild. Crate 350 MPIs are in the $5K+ range.

I've done several custom fuel injection systems. You just need to decide when to quit spending money. I would not change from a carb to a throttle body injection but changing to a sequential port injection system can give advantages, particularly in levelling the torque curve. If you want to try an tuneable aftermarket system these are some people I know who do a good job on a system you can install. http://sdsefi.com/
Repowering is an option. So is trading to a different boat.

Indmar just used the GM marine controller line. It's the same controller GM uses on many of their crate EFI motors.

Difference on your motor from a well tuned carb setup and well tuned EFI setup will be no noticble difference in max horsepower/tq. possible some increased power in midrange but not a significant amount.

Fuel economy may be slightly better but if you go aftermarket they don't get the same kind of leaps and bounds in fuel economy improvements that modern cars receive in their factory set ups.

The biggest benefit would be drivability. Things like cold starts/hot starts should be easier.

Is that worth $2k+ and the time to do the work? Wouldn't be to me but maybe would be ok for you.

I would think that retrofitting whatever brand would be on your motor would be the simplest but if you want even more DIying than the previous post give Megasquirt a try. Not for anyone who needs there hands held. This is their yahoo group.

http://autos.groups.yahoo.com/group/megasquirtnspark/

A fairly wonkish group so if you ask 'does this carburate better than a carb' you might not get an answer.

I hear that someone has cracked the Ford EEC-IV box and turned it into a cheap Haltech, which if true, could be very interesting.
Figuring out an easy crank fired ignition retrofit would probably help more than the FI.

(Message edited by roverjohn on July 07, 2009)