Mechanical or Electric Fuel Pump

[KRH1326]

Hi Guys,

I hope the boat weather was as nice for everyone, as it was on the LI Sound today.

My mechanical fuel pump, on my 1976 OMC 235 (235 HP) is on its last legs. I grabbed a small universal electric pump ( underpowered for my app. it gives 4-5 when I need 7-9 psi) just as an insurance policy to limp back to port if neccessary.

I am poised to make a purchase right now, but wanted some input.

I want to purchase a Holley Blue electric pump with regulator 14 psi max., and remove the mech pump and install blocking plate. Part #: 712-802-1

http://www.holley.com/712-802-1.asp

OR SHOULD I stick with the mechanical type, such as an AC or Carter, as Holley only seems to deal with Chevy now a days.

The only thing that spooks me about the Holley electric pump is the way that they recommend installation. They suggest that the flow order should be TANK-screen strainer/filter-PUMP-high quality filter-regulator-carb. (They claim that this pump is designed to push, not suck.) I have a standard Sierra cartridge screw on, screw off (oil filter type) type water sep/ fuel filter, and I am not so sure about pressurizing it, as opposed to sucking through it, as it is now.

What do you think?

 

[Don S]

Re: Mechanical or Electric Fuel Pump

Stick with the mechanical pump for your engine. The electric fuel pumps came out because of the EFI systems not able to control a manual pump. So the blocks on the engines were changed to eliminate the manual pump.
Your pump has been working fine for over 30 years. Why would you need to go to electric.
Besides, you need a MARINE electric fuel pump wired in properly so it won't run when the engine is off. Does your electric pump fit either catagory?

 

[KRH1326]

Re: Mechanical or Electric Fuel Pump

Yeah, I ran a dedicated wire from the ignition (as this is a project boat) so my emergency pump would work only when ignition is hot.

I was considering it, the Holley Blue ( it is a USCG approv.) just for modding the engine. One day I might drop a new electronic distributer in as well.

 

[KRH1326]

Re: Mechanical or Electric Fuel Pump

PS- If I blow up this engine, I can still use the electric pump on something else. Don't misunderstand, I have not made up my mind, that is why I'm asking for input.

 

[KRH1326]

Re: Mechanical or Electric Fuel Pump

PPS- In my pro list for the Holley Blue is that I can get repair/ renew kits for it. I can't for the mechanical pump.

 

[boatguya1]

Re: Mechanical or Electric Fuel Pump

Yeah, I ran a dedicated wire from the ignition (as this is a project boat) so my emergency pump would work only when ignition is hot.

I was considering it, the Holley Blue ( it is a USCG approv.) just for modding the engine. One day I might drop a new electronic distributer in as well.

Dedicated wire from the ignition means the pump will run as long as the key is on. If you have a fuel leak and the motor stops fuel will continue to pump until you turn the key off. This is a problem. Electric fuel pumps must be wired to an oil pressure switch to prevent this.

James

 

[Bondo]

Re: Mechanical or Electric Fuel Pump

I grabbed a small universal electric pump ( underpowered for my app. it gives 4-5 when I need 7-9 psi)

Ayuh,.... I've never heard of a Carb that needs more than 5psi....

 

[KRH1326]

Re: Mechanical or Electric Fuel Pump

Yes need to install pressure switch, will do if I go with the electric pump.
As far as fuel pressure, 7-9 PSI is right out of Seloc Manual appendix:

www.4shared.com/file/107233272/bc2fdd6d/specs.html

 

[Bondo]

Re: Mechanical or Electric Fuel Pump

As far as fuel pressure, 7-9 PSI is right out of Seloc Manual appendix:

Ayuh,..... There's the Problem.....

Carbs require 5psi....

 

[KRH1326]

Re: Mechanical or Electric Fuel Pump

Please elaborate.. I AM NO CARB GUY. Never have been. I have rebuilt many, many v8's, Can weld pipes and vessels that will hold 1000 psi, can wire the heck out of anything, built a cement mixer from a motor sprocket & flywheel and 55 gal drum, but I just can't get carbs.

If I don't know about something, I have to go to the book. Both Seloc and Clymers is quoting 7-9 psi on just about all Fords. Are these books wrong, or untrustworthy?

Thanks Bond-O

 

[Merc4ever]

Re: Mechanical or Electric Fuel Pump

I like the mechanical one because it's dependable... I would rather avoid more load on the electrical system and the possibilty of creating more problems with wiring. To me the less wires bouncing and rubbing the better.

Just my opinion, take it for what it's worth

 

[Don S]

Re: Mechanical or Electric Fuel Pump

Every carbed Chevy V8 motor used by Mercruiser that used a mechanical fuel pump requiered between 5 and 7 (depending on the pump used). OMC used the same GM engines and carbs as Mercruiser and Volvo. So why would their fuel pumps have to be any different than GM says?
Both Seloc and Clymers are aftermarket manuals and noted for the mistakes found in their manuals. All they do is copy information found in the OEM manuals.

 

[KRH1326]

Re: Mechanical or Electric Fuel Pump

OK I get the GM Chevy specs, and see that those numbers are right on for all of the specs that I can find.

I wonder if my Ford is the same. Did both Seloc and Clymers get Ford wrong with printing 7-9 PSI?

Thanks for the lessons, guys, I am learning.

I have changed my mind about getting the electric, and think I will get an AC mech, but will it drive me nuts if I don't get the 7-9 because Sel & Clym printed wrong values?

 

[Don S]

Re: Mechanical or Electric Fuel Pump

Ford Specs in the Merc OEM manuals is 3 to 6 psi.
The volume of the pump is what you need, not pressure. Too much pressure will cause flooding as it overpowers the float by pushing on the needle and seat.

 

[Maclin]

Re: Mechanical or Electric Fuel Pump

Too much fuel pressure will overrun the needle and seat's ability to shut off the flow into the carb bowl, and I can guarantee THAT will drive you nuts.

 

[KRH1326]

Re: Mechanical or Electric Fuel Pump

Got Ya, holy moley, don't believe it just because it was printed.

Thanks Don S

 

[Maclin]

Re: Mechanical or Electric Fuel Pump

Don beat me to it AGAIN