Fuel Pump
 

I NEED TO KNOW WHAT KIND OF FUEL PUMP YOU GUYS ARE RUNNING,I HAVE A 540 WITH THE STOCK FUEL PUMP MOUNTED ON THE SEA PUMP,SEEMS LIKE IT IS RUNNING OUT OF FUEL ON THE TOP, IT GETS TO ABOUT 4700 RPM AND STARTS TO FALL OFF TO ABOUT 4500 THEN BACK UP TO 4700 THEN SOMETIMES IT WILL BACKFIRE THREW THE CARB.I HAVE CHECKED THE FUEL PRESS. IT STARTS AT 7 PSI THEN DROPS TO ABOUT 5 AND STAYS THERE,BUT I AM WORRIED ABOUT VOLUME,STOCK PUMP AND STOCK LINES.
DOES ANYBODY RUN AN ELEC. PUMP AND IF SO WHAT KIND,OR DOES ANYBODY KNOW OF A GOOD HIGH PER. MECH. PUMP.

I'm running a electric pump on my boat, but because it has zero hours, I can't really speak much about the application. I've heard of people burning up the electrics when they don't use a return line, so that's something to consider. I believe that the mechanical pumps are something special and that you just can't swap on a hi-po one. There are a couple of threads on this topic in the tech section, so try a search. You may just find a answer to your question. I sure wouldn't run your engine long in this condition as you run the risk of damaging it.

BTW-I assume that you've checked the obvious like a kinked line or clogged filter.

I run Magna Flow 280 gph electric pumps with return lines.I had a 89 Convincer and the gas tank already had extra holes for return systems.On my new boat I had to install bulkhead fittings.

:eek: OHHHHHHHHHHHHH , you had better give that thing some fuel!! Go 1/2" fuel line from the tank back, and a higher volume fuel filter/seperator & fuel pump, at least 140gph.

Kenny,
I went thru the same problem , except I bought a Hi volume mech pump that replaced the stock one or so Cpperformance told me(still a little ticked about that) well thinking that I had sufficient fuel pressure it was the last thing I checked in trying to diagnose my problem . Motor had made 625HP (502) on dyno but wouldn't spin more than a 21 p prop. Well by the time I check fuel pressure (it wouldn't even keep float bowls full) it was too late and I busted a piston.

Now I run a Mallory 180gpm electric, at the time I think it was the highest capacity without a return line.

26Scarab, Went thru 4 Mallory 180's in 1 season,pumps and regulaters took a **** . Have been running Magna Flows for 3 years.you need to run return lines so the pump does'nt dead head and it also helps keep the pump cool.

THANKS GUYS, BUT ARE THESE ELEC. PUMPS THAT YOU ARE TALKING ABOUT ( MAGNA FLOW,MALLORY ) MADE FOR MARINE,OR RACE CARS.ALSO DO I DO AWAY WITH THE STOCK PUMP OR RUN A TEE INLINE WITH IT.I SEE NOBODY SAID ANYTHING ABOUT HOLLEY ELEC. PUMPS IS THIS BECAUSE THEY DONT MAKE MARINE PUMPS OR IS THERE A PROBLEM WITH THEM.

A friend runs mechanical pumps on a 800hp blown 540 inch motor. They are marine pumps, with diaphragm vent tubes and everything. He has no fuel supply problems but he does run 1/2" lines.

I'll try to find out who makes the pumps (they are polished).

You can by mechanicle marine pumps but I don't think that they are designed to run on the seawater pump! I believe you will have to run on the block if it has a fuel pump boss. I would check with Summit or JEG'S.
I have a 520horse 502ci that I run a Mallory marine electric pump with regulator and have had good luck with it, ran a Holley before and had problems and then it died!
I know that a 540ci making as much power as yours needs fuel! You should definetly be running 1/2" hose from the tank all the way. I ran 1/2" hose from the tank to the Electric pump and then #8 braided stainless from the pump to a high volume filter/seperator that I got from Eddie Marine. I then have #8 stainless to the regulator and a #6 line going to each fuel bowl from there.

Brian41,
4 pumps in one season ? that sucks. I understand about the deadheading thing but I can't plumb a return line without cutting out the tank and welding a bung in it. So far I've been lucky (66hrs) on the Mallory.

You can run Mech pumps only if you have a boss on your block , a friend of mine has some Nascar stuff on his 565's

If you don't have bungs in your tank for a return line hookup, you can install a tee in the tanks "vent" hose near the tank. Hook your return line to the tee.

I have been told that 5 to 5.5psi fuel pressure at WOT is okay. If it goes under 5 than you need to upgrade. Also may want to verify that your electric pressure gauge and sender are correct with a mechanical fuel press gauge.

Eric

It you want to run a mech. pump buy a Carter HV automotive punp and bolt the Carter bottom to the stock marine top. This is what CP performance sells as HV marine marine pump. This is what I use on my 540.

KChotboat,
That is exactly what I did and had just about Zero fuel pressure !


Checkmate,
I've heard about that but didn't know if it worked.

Mine works fine. You need to make sure the sea water pump is in good order since they do wear.

I was having problems with my Holley marine pumps (blue one and black one) The red pump would run all day, but you couldn't wind the motor up without the pressure dropping dangerously low. The lower output of this red pump apparently wasn't effected by the wiring.

After some resaerch, it turns out the problem was low voltage which can kill an electric pump. At WOT, there's no dead head problem, it's when your idleing that it causes the problems.

Turns out the long run of wire from the ignition switch to the safety switch and then to the pump was causing too much voltage drop. The solution, fuel pump relay. This mounts close to the battery and then gets a signal from the safety switch and then sends the voltage to the pump with a heavier and shorter run wire. Painless Wiring carrys them, part #50102, they're only about 25 bucks. You can see all the stuff they carry at www.painlessperformance.com

Craig

Ok, I called mallory with some questions regarding the filtering requirements of their pumps (forgot to install it before the pump and wanted to know how critical this error was). Anyways, the tech was adament that I would destroy the pump. I'm thinking return line-but the pumps have a internal bypass. The tech said that the gearotor style pump is absolutly incapable of lifting fuel. I asked about manually priming the pump and using a check valve. Doesn't matter. The pump can't lift the fuel. Basically, unless the pickup was below the tank and the pump was mounted below the tank, it would burn up. I asked how the pump would burn up. He said that the gear would gall on the aluminum creating too much drag and that the motor would over heat and fail. So of you guys running electric pumps, how many have had problems with the gearotor style when mounted above the tank?

KCHotboat, Do you know what the stock pump is rated at, as far as GPH? Verses the Carter HV pump? I also am trying to determine whether I need to feed my 509 more fuel or not. I don't think I do. My old Gaffrig fuel pressure gauge says 7psi at idle and 5-5.5psi at WOT. But I plan to verify that pressure with a mechanical gauge.

Eric

When I started looking for fuel pump answers Holley echoed the same thing as Mallory. The pump has to be mounted below the tank. I asked what pump he'd recommend for mine, and he said since they have to lift a little, he couldn't recomend one:confused: They make a "marine" pump, yet there's no application???? How many boats do you know of that the suction from the tank doesn't come out of the top. I thought this was actually a CG requirement, maybe not though. Anyway, I made a bracket that mounts the pump down at the bottom of the center pod, but it does have to do that intitial lift out of the tank. A lot of guys I know run them and they survive for years. They just have the relay that I spoke about earlier and so far, so good.

Craig

OK, 2 THINGS 1st I SEE ALOT OF GUYS SAYING TO RUN 1/2 IN FUEL LINE FROM THE TANK TO THE PUMP AND TO THE REGULATOR ARE YOU GUYS PULLING THE TANKS OUT AND CHANGING THE PICK-UP TUBE TO? MOST BOATS COME WITH 3/8 PICK-UP TUBES IN THEM, IF YOU LEAVE THAT AT 3/8 YOU COULD CHANGE THE LINE TO 2 INCH FUEL LINE IT DOES NOT MATTER,FUEL LINE SIZE GOES BUY THE SMALLEST SIZE IN THE SYSTEM,3/8 PICK-UP + 1/2 FUEL LINE ALL THE WAY TO CARB =3/8 FUEL SYSTEM.ONLY THING THE 1/2 INCH LINE IS DOING IS ACTING LIKE A LONG FUEL LOG.
AND THE OTHER THING IS THAT ELEC. FUEL PUMPS ARE MADE TO PUSH FUEL NOT SUCK AND PUSH,BUT IN ORDER TO DO THAT THEY WOULD HAVE TO BE MOUNTED SO LOW IN THE BOAT THAT THEY WOULD BE MOUNTED TO THE BOTTOM AND THATS NOT A GOOD IDEA.WERE ARE YOU GUYS MOUNTING THE PUMPS.

Mine are mounted close to the pickup, right on top of the tank. My pickups are 1/2".

I run the blue Holley pump, it is mounted about 1" above the tank. I have modified the pickup from stock to 1/2". The pump is wired off a relay, with a low oil pressure cut off switch. This has worked great for quite some time.

Kenny, I hear ya on the smallest hose restriction! Mine was changed over to the 1/2" lines, with the anti siphon valve removed for even less restriction, and fuel/water separator upgraded to high flow. I'm feeding a 1050 dominator on top of a blower using only the mechanical pump. Always have 7psi pressure. Actually, my gauge at the carb shows 9 at idle. I added a regulator to set at 7psi. Plus needed more red anodized chit! :D

Now my thought/question.............

Okay, now we all have these big unrestricted 1/2" fuel lines, up graded to the high flow fuel water separator, removed anti siphon valves, some with electric fuel pumps in addition to the mechanical pumps..............and feeding what..........2, maybe 4 fuel needle & seats that are only .125" ID in dia each (and that is erroring on the larger side, .093 more realistic). That's not counting the restriction from the needle itself, so actually even less!!! And to top it off, that is thinking that the needles are fully open all the time. Has anyone ACTUALLY have some 1st hand experience on any improvements by upgrading the fuel lines to 1/2"?

I'm all ears on this as it has never made since to my simple little mind. ;)

Thanks

The HV carter is rated at 6-8 psi and 120 GPH. Mine reads 8 psi at the carb and 6 on the dash. Because of some other fuel problems I had I have a holley elect. pump as a feeder pump.

US1Fountain;

I personally don't have any first hand experience to talk about, but this is my opinion anyway.

I understand your thoughts. If you do the math it agrees with your theory.
1/2'" fuel line = .19625 square inches.
.125 needle and seat=.01226 square inches.

Say you have a single carb. running .125 needle and seats. Thats only .02452 square inches ( the area of both the needle and seats) of area where fuel can flow into both carb. bowls. Why do we need .19625 square inches ( the 1/2" line) of fuel to feed only .02452 ( the 2 needle and seats)???
The only reason I can figure is to make sure that there is enough fuel volume at the needle and seats so the jets don't suck the bowls dry.
When your motor is spinning at 5000 rpm and under a load, the fuel is being sucked in, not pushed in. There is no fuel pressure in a carb. bowl. So fuel is not pushed into the motor, the motor draws it in by vacuum. The fuel pressure is in the lines before the needle and seats forcing fuel into the bowls. I would imagine that is the reason why the small hole of the needle and seat can feed the larger combined holes of both of the jets in a metering block. BUT, you need the pressure to force the fuel pass the needle along with having enough of a volume of fuel so the bowls don't run dry.
So, what the hell am I trying to say?? I think that you need a larger diameter fuel line to feed the motor. Especially for a worked motor. It is better to have too much fuel at the needle and seat than too little. The motor will only use what you allow it to use by your regulating the jet size anyway.
I am not saying that you don't think that a 1/2" line is a good idea, I am only trying to convey my theory on this.

WOW THIS IS GETTING DEEP.
DO YOU REALLY NEED 1/2 FUEL LINE.LOOK AT FUEL INJ. MOTORS THEY HAVE 5/16 FUEL RAILS I THINK? BUT THEY RUN 40 PSI PRESS.

ELECTRIC PUMPS
 

I RUN 2 HOLLEY MARINE BLACK PUMPS ON MY RIDE-THEY ARE FED SEPERATELY WITH 1/2 LINES(#8) THEN TEE INTO SINGLE #10 LINE THAT FEED MY B/G 4 PORT REG (NO RETURN)NO PROBLEMS AS OF YET(KNOCK ON WOOD)--YOU COULD JUST CATCH A GLIMPSE OF THEM IN THE PICTURE SECTION--UNDER HEART OF MY CAT....

I don't think that you can compare a fuel injection system to a carb. As I said in my previous post, in a carb. you are relying on the vacuum to suck fuel down a carb. venturi. I don't know how many inches of hg that an engine creates through the venturis' but I would venture to say that it doesn't equate to 40 P.S.I. as in an injection system. In injection, you have all that fuel pressure built up sitting at the pintle waiting for the ecu to fire the injector coil, when it does the fuel will be forced down into the intake very near the head. Not only is there alot of pressure here, ( 40 psi as compared to 6psi at the carb needle and seat) the amount of fuel is regulated by the ecu, and is squirted nearly directly into the head, as opposed what ever falls down through the carb venturiis' , mixes under the carb, then drawn down the intake, through the head and finally into the combustion chamber.
In efi, the fact that the fuel is shot in at the end of the intake manifold would definetly affect the characteristics of the air flow in the intake due to the air being dry for almost the entire run. This along with the fact that the fuel is sprayed in and its' mixture more closely regulated by the e.c.u., would promote better atomization of fuel. I feel that these 2 facts are part of what allows an e.f.i. system to run leaner and still be safe.
How the hell did I get onto this?:confused: :confused:
It seems that I have gone off on a tangent somewhere back after my first sentence.
Oh well, for what it's worth my .02 says that you can get away with a smaller line in an injected motor just because of the nature of its' design.

I didn't know this thread was going on before I started another one. I would be interested in your comments on my fuel pump dilemma.



[URL=http://www.offshoreonly.com/forum/showthread.php?s=&postid=340332#post340332]

Cord
 

I too went throught the delemma (sp) of wondering how I would get a electric pump to work above the tank. I have used a mallory 140 and now a 250 with return and have had no problems. In about a second or two, the pump builds pressure, meaning, it obviously sucked the fuel the 12-15" from my tank (vertical distance only) and pressurized it. I did however have problems with a deadhead regulator sticking after a wot run. Return style works great.

THANKS BRAD! I've been stressing over my installation, for some time now! I finally decided to just try it-if it didn't work, I'd replumb. In your application, are you running a coarse prefilter and a check valve? I was thinking of adding these to my setup.

For those of you that are bolting a Carter HV pump (model M4889) to the stock botton - are you tapping out the supply and return to make them bigger? They are only 1/4" lines. (I've got two of them sitting here in front of me).

TTT

The Merc mechanical fuel pump used on the HP465/HP500 is the exact same pump used on the SC600. That ought to give you some idea of the amount of HP it is designed to support - and it does it through 1/4" fittings. If it's not working there may be something else going on...

Be sure that there are no air leaks in the fuel line/pickup within the tank that prevent the fuel pump from sucking fuel only from within the tank. Many tank/pickup assmeblies leak air where the pickup meets the fitting within the tank preventing efficient operation of any pump.

Kenny,
I have a pair of 540's and was using the a Holley mech fuel pump part #12454-11 which really sucks!---or maybe I should say they don't suck enough. Anyway the Holley's didn't work for me. I switched to a Edlebrock mech pump #1712. They have 6 valves internally vs. only 4 within the Holley. However, you must run an external fuel pump regulator on the Edlebrock. I was told to buy the Holley fuel pump regulator because they are a good regulator and work well. I have mechanical oil filled fuel guages on my dash for each engine. In other words, I have -4 braided fuel lines going from the carbs all the way up to my dash at the helm---kinda scarey, but anyway I always monitor my fuel pressure at the helm as the boat is running on plane, under load and at all RPM levels. I have not run my engines with the Edlebrock pumps yet, but my cousin had his engines on the dyno with the same Holley fuel pumps that I had just switched to late last season. The pressure on the dyno could NOT keep up---whatever the problem was the Holley's performed poorly! We switched to the Edlebrock pump while my cousin's engine was still on the dyno and the Edlebrock pump did a great job. So, I had them installed on my 540's and will be running them here very shortly.

BTW, I am running -8 fuel lines from the tank up to some new Keith Eickert coalesant fuel filter/water seperators to the Edlebrock pumps, to the Holley fuel pump regulators and each line coming off the regulators are being fed to the carb bowls. In other words, each bowl on the carb has its own fuel line from the fuel pressure regulators. -8 all the way. I'll try and post a picture of it.