Carburetor to Electronic Fuel Injection Conversion ???

[valcokid]

I have an early (1984) Merc 5.7 L small block V-8 that is carbureted, (small for a 260 SRV) my home water is at 7800 feet elevation to boot. It is a bit under powered to start with and this elevation doesn’t help the issue.
I am not interested in refitting with a new power plant.......yet.
I would like to hear if anybody has any experience with converting the Quadra jet carb to an electronic fuel injection system. I have heard that it would be an increase in horse power and fuel economy as well as less fouling, smoother running, etc...

Any thoughts would be appreciated!
Thanks, Barney

 

[valcokid]

OK ... I think I have found the answer.
http://www.affordable-fuel-injection.com/index.php?id=18&title=Marine+Fuel+Injection+Systems

It looks like a cool $2,500 and I am all set, except for labor "Oh Boy"! That may be the scary part.

I have to admit, I am a bit suprised no one has chipped in on the subject, has nobody tried to do this?
Have I lost my mind?

 

[PMC]

I have to admit, I am a bit suprised no one has chipped in on the subject, has nobody tried to do this?
Have I lost my mind?

I've done this in an automotive application (not the same model you are looking at), and tuning has been tough. :smt013Conceptually the idea is great - when it come to the execution...lots of time spent. I'll go back to a carb any day.

Would I do this in a boat - no way. Simple is sometimes better.

 

[rondds]

For that coin would it just make sense to re-power with what you want? That's a big investment in a pretty old motor. My thought is "no way!"

 

[Spot]

I was thinking about doing the same thing on my Jet boat. I had a Holly which always had challenges. Like you, I did research and found that a new Edelbrock carb would help out with the gremlins and actually improve power.

Lets see $2500 boat bucks or $350 boat bucks on an older motor. I did the Carb and totally happy with the results. This was on a Kodiak motor not a Merc but it should be just as easy?

 

[fc3]

Find someone who knows carburetors (speed shop) and have him rejet the carb you have for high altitude. Much cheaper. Nearly as good.

 

[sprink56]

Find someone who knows carburetors (speed shop) and have him rejet the carb you have for high altitude. Much cheaper. Nearly as good.

+1:thumbsup:

 

[valcokid]

Ah, boat bucks, this is a very good point, one that makes sense now that you put it that way, dollors spent on a boats IS a bit different.

I will have to reconsider the EFI investment, after hearing about the time spent trying to get it tuned in... I will keep you posted on the next step.

 

[valcokid]

I like the cost of the re-carb approach, and believe I will try that route first for the minimal cost. The increase in horse power over the stock 260 was one of my larger concerns and don’t believe the new carb will provide the kind of increase that the EFI package would. But hey! it's not $2500 either. I can't wait to see what the re-carb effort will yield.

Just for the record my WOT is a mear 3400rpm on 91 octane, running a 16 x 13 prop. At this RPM she will barley break a plane. With the trim and tabs tweaked to max performance.
So my plan is to install a NEW re-jetted carb, electric fuel pump, and electronic ignition.
I will update, as soon as I get the parts together, and get'r done.
Thanks for all the great feed back, this is truly a valuable site! :smt038

 

[rondds]

Even at that elevation, that RPM is too low for that engine. Even back in 1984, that motor should turn closer to 4200rpm at WOT? Really dumb question but could it be your prop?

 

[fc3]

Even at that elevation, that RPM is too low for that engine. Even back in 1984, that motor should turn closer to 4200rpm at WOT? Really dumb question but could it be your prop?

Unless there is something seriously wrong with the engine, it's the prop. At sea level, my old 26 footer ran a three blade 15x15 prop. I'd expect a bit less at that altitude.

 

[valcokid]

So are you guys thinking that the 3 blade 16 x 13 is not enough of a drop? The next available size from merc would be 15 x 13 from what I have been told by my local shop. In a few other forums I have read that at sea level the 260 performs in the 4200 -4600 range w/ a 15 x 15 factory prop. The boat came from Doboque, Ill. equiped with a 5 blade SS 13 x 17 before I removed that prop I was pulling 2200 rpm wot. Thats when I switched to this 3 blade 16 x 13 aluminum. My local shop feels like I will be doing good to get into the 3800 rpm range at this alltitude...?
I am going to check timing. Factory specs 8 BTD and my shop says go to 10 BTD for the elevation., the engine seems to be running well, a little rich, maybe this will help? I sure would like to hear if there is a better prop suggestion...