efi to carb conversion
#11
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carb conversion
i plan on doing the swap myself.carbs i understand,efi i dont.i am not sure if efi will make more h/p over a carb.i know the efi will use less gas.and another thing.when and if i decide to get more h/p out of my carb motor,its not going to be that much of a hazzle,no re-mapping the computor,changing to bigger injectors etc.i also think as said,a much cleaner apprance in the compartment.and i know the parts are aLOT cheaper.i know some of you guys think this is foolish,but its all about what i can work on and what i feel comfortble with.thanks for all the input.
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The stock 502 carb motor was 1 to 2 miles slower, I had one its 415hp to 390hp. What I did was save up buy a custom carb 1000 to 1500, intake brodex or dart are the best for hp. if you can spend a extra 400 on the intake have DEAN GELLNER set you up with custom carb 700 to 1500 /custom intake 800/ roller rockers 300/ cam springs lifters 1200/ plus labor you should end up with 600 to 650hp, that will last 400 hours plus as long as your bottom is good. this is what I had with some combos 390hp/585hp/595hp/637 hp/647hp/ 670hp all started with stock merc 93 502/ did the bottom blew printed and new heads at 637hp and up. now going to his intake carb going for 700hp or add cam and more like 725 . but Dean will hook you up right. I went from 67 gps to mid 80's.
#13
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whats the problem anyway?
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#14
Yep, it would help to know that.
And are you sure the problem with the engine is with the EFI?
If it's a stock 502 it seems a qualified Merc mechanic would be able to diagnose and then take care of the problem.
I don't agree that, in a single engine boat, you're going to loose 5-6 mph if you go to a carb. And as with most any engine, if it's set up properly, reliability shouldn't be a problem either. I've had conversations with a couple of builders who I know pretty well and who are familiar with both carb and EFI and was told that a carb engine tuned/set up properly will produce as much power as a comparable EFI engine. However, I have no personal experience.
Originally my boat had a carbed 7.4/330 in it and it ran flawlessly. The 7.4 was yanked and replaced with a ZZ502/502. I had Nickerson's marinize the carb that came with the ZZ502, and the engine ran flawlessly for 4 seasons, of often very hard running. Last season the ZZ502 was bored and stroked to a 557. It now has a relatively mild rmbuilder tight lash solid roller and a Nickerson Dominator. I only had the chance to get out on the water with it 3 times last season, but it ran very well. And I high idled it a few times (+,-1000 RPMs) for better than a half hour at a time, and the engine would spring to life when I went for the throttle.
That said, I don't understand EFI/computers either so I too prefer a carb engine. My thought is, if you have EFI and if you have someone close by to service the engine, then EFI is probably the best way to go. It's all a matter of preference, and access to someone qualified to service the engine/system. JM .02
And are you sure the problem with the engine is with the EFI?
If it's a stock 502 it seems a qualified Merc mechanic would be able to diagnose and then take care of the problem.
I don't agree that, in a single engine boat, you're going to loose 5-6 mph if you go to a carb. And as with most any engine, if it's set up properly, reliability shouldn't be a problem either. I've had conversations with a couple of builders who I know pretty well and who are familiar with both carb and EFI and was told that a carb engine tuned/set up properly will produce as much power as a comparable EFI engine. However, I have no personal experience.
Originally my boat had a carbed 7.4/330 in it and it ran flawlessly. The 7.4 was yanked and replaced with a ZZ502/502. I had Nickerson's marinize the carb that came with the ZZ502, and the engine ran flawlessly for 4 seasons, of often very hard running. Last season the ZZ502 was bored and stroked to a 557. It now has a relatively mild rmbuilder tight lash solid roller and a Nickerson Dominator. I only had the chance to get out on the water with it 3 times last season, but it ran very well. And I high idled it a few times (+,-1000 RPMs) for better than a half hour at a time, and the engine would spring to life when I went for the throttle.
That said, I don't understand EFI/computers either so I too prefer a carb engine. My thought is, if you have EFI and if you have someone close by to service the engine, then EFI is probably the best way to go. It's all a matter of preference, and access to someone qualified to service the engine/system. JM .02
Last edited by Kidnova; 04-25-2009 at 04:21 PM.
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symptons
when imrun the boat for awhile and shut it off for about a hour,the motor will start,idle like crap,like it has a cylinder out,instead of a smooth ldle,it seems like i have enough fuel to almost get on plain,and then it starts,motor dies,picks back up and then dies agine,some times it picks back up,sometimes not and then will barely run.lately this will happen when i am idling through a no wake zone.temp is normal,140,oil temp 220-240.i have a set of gages on the motor now.one on the suction side of the mech.pump.one at the vst tank at the inlet.and a high pressure gage on the fuel rail.this should tell me if the fuel system is at fault...i hope.i rebuilt the motor last year and had the same problem but just not as bad.i feel it is fuel related because how the motor sounds.....running out of fuel.i just hate paying someone to work on my stuff when i can do it myself...a carb that is.
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when imrun the boat for awhile and shut it off for about a hour,the motor will start,idle like crap,like it has a cylinder out,instead of a smooth ldle,it seems like i have enough fuel to almost get on plain,and then it starts,motor dies,picks back up and then dies agine,some times it picks back up,sometimes not and then will barely run.lately this will happen when i am idling through a no wake zone.temp is normal,140,oil temp 220-240.i have a set of gages on the motor now.one on the suction side of the mech.pump.one at the vst tank at the inlet.and a high pressure gage on the fuel rail.this should tell me if the fuel system is at fault...i hope.i rebuilt the motor last year and had the same problem but just not as bad.i feel it is fuel related because how the motor sounds.....running out of fuel.i just hate paying someone to work on my stuff when i can do it myself...a carb that is.
Last edited by Boat Tech; 04-26-2009 at 03:16 AM. Reason: forgot temp
#17
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fuel pump problem??
i ran the boat today and it messed up.this time i had the chance to read the gages.i had no fuel pressure on the fuel rail.i could hit the bleed valve on my gage and get frof and then nothing.the motor is running,well trying,and no high pressure.the pressure on the mech. pump was 10psi.after awhile of cutting on and off the pressure builds and the motor clears out.vapor lock,i know.i allways knew.how do i stopit.new pump?the boat was run 1hour and cutt off for about ahour.any fix?
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i ran the boat today and it messed up.this time i had the chance to read the gages.i had no fuel pressure on the fuel rail.i could hit the bleed valve on my gage and get frof and then nothing.the motor is running,well trying,and no high pressure.the pressure on the mech. pump was 10psi.after awhile of cutting on and off the pressure builds and the motor clears out.vapor lock,i know.i allways knew.how do i stopit.new pump?the boat was run 1hour and cutt off for about ahour.any fix?
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i ran the boat today and it messed up.this time i had the chance to read the gages.i had no fuel pressure on the fuel rail.i could hit the bleed valve on my gage and get frof and then nothing.the motor is running,well trying,and no high pressure.the pressure on the mech. pump was 10psi.after awhile of cutting on and off the pressure builds and the motor clears out.vapor lock,i know.i allways knew.how do i stopit.new pump?the boat was run 1hour and cutt off for about ahour.any fix?
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