502 mpi thoughts on pitching injection and going with the carburetor
 

Just bought my first boat of this type just wanted to get some thoughts on keeping or losing the fuel injection going with the carburetor seems like there's a lot of issues with the MPI injection and if I ever wanted to go supercharged seems like it be a lot more money than a simple roots style blower carburetor any thoughts

Both have pros & cons. When EFI is working right it's great, but unlike a carbureted engine trouble shooting is a bich..
MY 2¢

Alot of us have done it, especially when adding power - heads, cams, etc.

You can re-use the EFI distributor too. Has a module inside with a decent advance curve.

Just did the change over from EFI to Carb....after building more HP. Really happy with the change...lot less issues dialing things in and cheaper. Good luck whatever direction you choose.

Did it my self because of running a procharger and the mix of the merc EFI and that does not work well without lots of changes, ran 2 seasons carbed, worked well, now built our own EFI system and now back to EFI, but far from the merc deal...

You should do a build thread.

If you have a 502 mpi mefi 3 (assuming by your signature having a 2002 boat) there is alot that can be done with it and in 14 years of running the mefi 3 then 4 efi I have never gotten towed in because the efi itself or ecu quit, made 650 hp thru it NA and over 1100 blown with mods. I wouldn't go backwards to a carb unless there is a fundamental problem already / major component that needs replaced , Smitty

You could just go to one of the after market self tune ECU's and be done with it. Make any engine mods you want, use your stock manifold, injectors, throttle body if you want, tune real time.

I would save my money and redo the fuel system with a single big pump and regulator, new fuel line and a RETURN LINE like merc should've done. Then put mega squirt EFI on it with a ProCharger

:evilb:

Just did this all this year, and finished my boat two weeks ago! I'm very happy with the carb and have always been a carb guy anyway, plus the look factors helps! Love it! I say do it during the down season! Here's mine! There is a Video of it running in on one of the pages also http://www.offshoreonly.com/forums/s...-restored.html

CNC AKA Randy Fedo paid to have carbs "professionally" done by one of the "top" name carb companys for his blown 565's, after 2 seasons of chasing lean spots, tuning issues and overall pizzing around he installed mefi 4b's and his boat never ran so good, maybe a roots supercharger would be great carbed but a procharged motor with blow thru carbs is a compromise at best, keep in mind you have to have main jetting and fuel metering big enough so that it isnt lean ANYWHERE but you end up with rich spots where with efi you tune for every map setting not to mention being able to tailor timing not only to rpms but load/map settings. Normally aspirated running at the same altitude and most time same temp, sure, a carb would be fine. BTW, here is a vid of dyno pull with modified mpi intake, Smitty
https://www.youtube.com/watch?v=dDxk...DKzQCciuZ-a5mA

I agree Smitty.

I love carbs for most everything, but for blow thru I'd do programmable EFI.

The few blow thru systems I seen with carbs were horrible pigs and ran like total **** even after having carbs done by the best!

I haven't had a carb since '97 and like others have said, EFI is going to be easier/better (now days) for blown applications. I must admit though, I am constantly amazed how nice carbs seem to work on boats in N/A applications from stock to FAIRLY hot. Honestly, the EFI for me has been less reliable over the years, ( not too bad) I would like to try one more motor with one of the newer Holleys. N/A of course!

EZSTRIPER : Can you give me some details of the EFI system you built? I'm looking to do the same.

EFI is great for cars and trucks but I'm not quite sure it always stands up to the abuse in a marine situation. If you start having running/performance issues, unless you know your schit and have the right software, most are at the mercy of a marine or marina mechanic which is not always a good thing...especially if there are mods to your engine. Or, you can pack your EFI stuff up and send it across the country to have it reprogramed....never any problems with that, right?? LOL. I dunno, I guess if I had a newer boat with efi and a stock mill I'd leave it as is. But if I was going to mod the engine and there wasn't a local trusted EFI guru then I'd go carb.

OP - A period at the end of a sentence is a good thing and makes stuff easier to read.... just say'n....wink wink