Do You Use an Electric Fuel Pump?

[Oz Dude]

Hi All,

We were discussing this the other night while working on the boat. I used to run a Mallory electric pump on my old setup (Carby 3L Merc) and never once had a fuel problem in 8 years and could ping the rev limiter every time I went there. With the new setup (Injected 3L) I was told there was no need to add a separate inline "push" pump but I have a sneaking suspicion that we're running a bit lean in the top end.

The issue is more pronounced the shorter pitch prop you use but for example, with a 21P Laser II, running at about 45mph and punching it, the boat runs real hard up to 75mph and then you feel it "crest" and it comes back to 71 with the throttle pegged. You can't get it back up there unless you bring the revs back down, cruise, then punch it again. Does the same with higher pitch props but not as noticable.

A mate of mine is having similar issues with his boat and it's also an injected 3L. But here's the thing. You talk to one mechanic and they say "not needed, don't put one on, blah blah blah" but the next one you speak to says "I put push pumps on all my setups"... So far out of 6 mechanics, we're split 50/50 which I think is quite interesting.

We're gonna wire one in and see if it helps the issue (in either boat) but I wanted to know from everyone here on the boards if you run a separate pump and if so, what motor combo do you have? Also, did you always run one or did you put one on later and found improved performance?

Thanks,
Oz

[Rodney Nance]

If it is lack of fuel it should run worse with the larger prop because more load needs more fuel. I have heard that the injected 3 liters with out a correct load on them will miss and lose power. You may have a set up problem. I would run a fuel pressure gauge off of the fuel rail and see what I had at WOT. You may just be hitting the rev limiter. If the pressure is good I would try a bigger prop and see what happens. I don't know what boat you are running but a 21 pitch prop seems small.

[Oz Dude]

Thanks for your input Rodney. Yeah, I was using the 21 as a "benchmark" point for where the problem is really noticeable. With a 26 and a 28 you can still feel the crest but it's a lot slower and less variance.

More overly looking to see who runs electric pumps, what sort they use, and if they have always run them or was it an add on...

Oz

[T-REX]

Tha stock pump should be sufficient to supply your mota while operat'in in tha recomended rpm range...Mercury ain't gunna go out on a limb, and take a chance on burn'in a mota that they will have to replace under warrantee!!...This iz juss my unprofessional opinion...

3liters are an animal ov thier own ta me...Tha elecktroniks on them juss do weird thangz, and take all tha tunability away from a normal mekanik...Your mota retards time'in when it actually oughtta advance it, it iz limited in wayz ya kan't understand(or I kan't)...All and all, tha 3liter run purdy well for all tha junk dezigned to make it no blow up, or not be able to hot rod!!!...

Rodney hit tha nail on tha hed az fer tha load deel....

I run a push pump on most everthang, mostly for tha reason ov eliminate'in tha bulb, and I know it KAN'T HURT!!!....But, I have never been know'n ta be politiklly correct!!!:thumbsup:

[LakeTrash]

Take Rodney's advice and install a fuel pressure gage in the high pressure circuit. You cannot evaluate a fuel injected system without one.

I will also agree with Rex in that a pusher pump is not required and that you will find your proplem is in the electronics. I think I have as much 3.0 experience as most and the crap that system does and why it does it is still a mystery to me.

LT

[Da Bull]

Before you wire in the electric push pump you could just simply have a bud ride in back with squeeze bulb in hand and pump it when you get to the problem rpm. This would answer your question but Rodney and LT is right about having a fuel pressure guage.

DB

[Shaun Torrente]

The pump in the VST could be laying down,,, I have fuel pressure gauges on both of mine and before i put fuel pressure regulators on them the motors would start @ about 40psi running and 15 minutes later they would be down to 30-34 psi... I put new pumps and it did the same thing until i added the FPR then i could bet it to hold 40 psi all the time by starting out with a base of 44-45 psi...

I use a B&M FPR that is actually for a honda... Any spped shop will have it and is about 45-60 bux

Shaun

[THE HOGG]

I TALKED TO ERIC SIMON ABOUT MINE AND NOW HAVE A HOLLEY PUMP FEEDING THE VST. CURED MY PROBLEM. GOT A CUTE LITTLE SIMON PLATE TO COVER UP THE HOLE FROM THE STOCK ONE EVEN:p

[Oz Dude]

Ok, I'm sensing that the electronics are, ahem, not entirely to everyone's liking :)

With adding a fuel pressure gauge , what sort of pressure should I be seeing?

Shaun - where in the system did you add the FPR and if the system was at 40psi to start with, how did you get it to perform at a starting pressure fo 45psi?

The Hogg - when you say you got a plate to cover up the stock one, I'm guessing you mean you removed the fuel pump from the motor all together and now your Holley acts as the push pump all the way to the VST?

I gotta say, when I saw the "new" motor for the first time complete with squeeze bulb I wasn't overly happy. I can't see how technology from the 1970's should still be applying to current motors. I don't have a squeeze bulb in my car, I have electric pumps at the tank that push fuel to the motor, hence my reasoning that my Merc setup should be the same...

Thanks for the thoughts and feedback guys.

Oz :thumbsup:

[THE HOGG]

Correct. I Removed The Stock Fuel Pump And Now The Holley Pushes To The Vst. If I Remember Right Simon Said That He Had Heard Of A Few Having Slight Starvation Problems Running Wfo. I Was So I Changed And It Solved The Problem. You Should Give Eric Simon A Call, He's A Great Guy To Talk To And Will Help In Anyway He Can. He Also Understands The Electronics As Good As Anybody Imho And Can Change Whatever You Want In The Computer.

[Oz Dude]

Thanks Hogg :)

Oz