Electric Fuel pump-vs- stock pump

**B.Mac** · 10-09-2001, 06:22 AM

I'm getting advise to "chuck" my stock fuel pump (200/ 2.4 w/ relieved exhaust) and install an electric pump. I run 80MPH @6100 w/ a 28P ChopperII and I have'nt noticed any lack of fuel @ WOT with the stock pump but I'm being told I have minimal (1-2 lbs) fuel pressure at WOT and I should have more. It's also been suggested that I prop down to a 26P and spin up to 7000 and increase my speed by 5-8 MPH. To be honest, I'm just short of freaking out right now at 80 and I've always been told to run that motor under 6200 if I want it to last. I'm strictly a recreational speed freak and I need to make my powerhead last forever (according to my wife, and my wallet). Any input is much appreciated.....B.MAC

**Raceman** · 10-09-2001, 07:10 AM

First, if you're turning a 28 in the low 6's now and drop pitch it's very unlikely that you're gonna pick up top end speed. As a matter of fact, for pure top end it's more likely that you'd pick up speed with a 30. I've never been an RPM junkie. Again, it's good for acceleration, usually bad for top end, fuel economy and longevity of parts. How was it determined by the advisor that you don't have adequate fuel pressure? If the fuel pump is in good shape it's certainly capable of feeding 6100 RPMs. A carb motor needs one thing from the fuel pump: proper volume so the float bowls don't run low. All they are is reservoirs just like the tank on a toilet. As long as they stay full, it doesn't matter how much pressure filled them as long as it's suffiecient to pass fuel INTO the bowl and not high enough to blow needles off the seats. With proper volume, the pressure within these two ranges is irrelevant.

**Liqui-Fly** · 10-09-2001, 07:52 AM

Sounds to me like you're running pretty good right now. If you do decide to go with an electric pump a Holley Red pump might be your best bet. This is if you don't have oil injection. Some say to drop the pressure down to 3 to 4 psi's while others say 5 to 6. I'm running mine unregulated and it puts out 5 psi's just like it's supposed to from the factory. The only honest upside to running an electric pump is not having to pump a ball anymore. Your motor would let you know if it wasn't getting enough fuel. LF

**mercrazy** · 10-09-2001, 07:54 AM

i prefer keeping things as simple as possible. some people don't. they like to add all the bells and whistles and love tinkering with all the complexities of their creation. if you periodically replace the pump diaphram, eliminate all fuel line restrictions, and run the engine in the suggested rpm range, the stock pump should be sufficient. if it wasn't, mercury would have used electric pumps to start with like they do on the hi-performance motors. the diaphram pump can't pulse fast enough at high rpm. but now if you want to start tweakin on your motor and turning higher rpms to see what it will do, you should get an electric pump. you're going plenty fast in that boat already and the first time you hear that knock, knock, knocking sound, you and your wallet will wish you had left well enough alone. unless you're actually racing where every mph makes a difference, the risk isn't worth the reward. i've been there - done that.
darn, i must be getting old. after reading over my reply, it sounds like some old miser's response.

**jody** · 10-09-2001, 09:40 AM

I have a 135 Mariner I run a Holley electric pump I turn my motor from 6400 with a 28p to 6800 with a 25p. I run it a 4 psi and have had no problems knock on wood. Just my two cents.

**us1** · 10-09-2001, 09:55 AM

The stock pump is fine for 6100 if you are going to turn a lot more you might want to change. I have to agree with Raceman the smaller prop will slow you down. If you want that motor to last just leave things the way they are.

View Profile · 10-09-2001, 01:12 PM

hehehe

That's a first!

Electric baby! Holley red/blue pump all the way. (Many other brands as well w/ regulators)

For one, I have to also disagree with Raceman. It is more than just volume and pressure. It's also the way the fuel is delivered. Is it pumped in erratic spurts that cause turbulence and air bubbles in the carb bowls or is it pumped in a controlled laminar flow pattern like an electric pump does?

It's NOT that much more complex for the piece of mind. Also, I'd like to see you use the stock pumps to empty your fuel cell in minutes flat when it needs to be removed from the boat for whatever reason!

I raced with Quadrajets for years. One of the most advanced carbs ever made. Every ignoramus out there said the bowl was too small. Bologny! The bowl was perfectly designed to hold a proper level under all conditions, it just couldn't handle the "spurting" action of a mechanical pump. It needs the smooth flow of an electric and then it works awesome.

-BL

**us1** · 10-09-2001, 03:28 PM

Sure there’s always something better, but a stock motor at stock RPM should run on a stock pump.

View Profile · 10-09-2001, 04:14 PM

Actually I do agree.

I tried to use the stock pumps on my 2.6XP for that reason. When I found out they were bad and it almost cost me a destroyed motor, I weighed rebuilding the stock pumps and dealing with soft bulbs and silly plastic valves with the piece of mind of a Holley red pump that can feed a 400-500hp big block on nitrous.

The choice was clear.

-BL

**Raceman** · 10-09-2001, 04:26 PM

I don't know how quadrajets behave with pulsing mechanical pumps and they may very well have to have excellent flow if the size of the reservoir doesn't have much reserve in relation to the requirements of the motor. Merc carbs do not fall into this category when meeting the requirements of a 6000 RPM stock motor. Also, fuel doesn't hold aeration to the extent oil or other heavier fluids might. 5 lbs of fuel pressure won't do any better than 2 lbs in a merc carb if the volume is sufficient. Also with proper volume, the needles will cycle through open/closed even at full throttle. This in itself will absorb mechanical fuel pump pulses somewhat.

**Raceman** · 10-09-2001, 04:30 PM

And one mo thing......the reason I don't have any experience with quadrajets is that REAL performance cars all came with Holleys, HaHaHa. (I can't make myself type LOL)

**woodco** · 10-09-2001, 04:42 PM

On all my stock V-4 and V-6 OMC motors we always ran electric
pumps instead of manual.Never had a problem with fuel flow or efficiency ( what's that word ) , I guess it's up to the individual to make their own choice but one thing I did change was the bypass
of the oil injection pump.

**Techno** · 10-09-2001, 05:03 PM

One advantage is no more squeeze bulb, this is almost worth it all by itself.

Raceman, which 'Vettes came with a holley? The only one I can think of is the race version that was incorrectly listed as 430HP and actually put out around 650HP.
Notice that holley copied the spread bore concept.

**woodco** · 10-09-2001, 05:17 PM

Never found a Holley that was dependable.You could never keep them tuned. " Just my opinion " or should I say " Past Experiences "

View Profile · 10-09-2001, 05:20 PM

I knew that one was coming!

The main disadvantage of the Quadrajet was that it was either on the primaries or wide open. Partial secondary usage is poor because the butterflys for the secondaries are so large they tend to redirect air flow at less than wide open positions.

It is true though that a larger bowl will give the fuel time to "calm" down.

-BL