Fuel pump,opinions wanted

[Buttanic]

I am considering mounting an electric fuel pump in parallel with the mechanical engine driven pump. I would wire it through a manual on/off switch. My reason for wanting to do this is two fold. One is to have an immediately avaiable back up in the event of failure of the mechanical pump. Two is to prime the carburator float bowls when the boat hasn't run for several weeks and the bowl have dried up. I go off shore with a single engine like to be prepared. A failure of the mechanical pump in heavy weather could be a catstrophic situation. The ability to quickly switch to the electric could save the boat. I know I could carry a spare mechanical pump but changing it requires time which I may not have plus spilling of fuel in the boat.

 

[achris]

Re: Fuel pump,opinions wanted

Hi Buttanic,<br /><br />You should consider having some sort of isolating tap(s) between the pumps. If, for example, the mechanical pump split a diaphram, then without a tap to isolate it the electric pump would just suck air through the perforated diaphram, not fuel from the tank. You'll also need an automatic shut-off on the electric pump, if the engine stalls. Mercruiser do it with a normally open switch on the oil gallery. If there's no oil pressure the pump stops running. I think you'll find it's part of the Coast Guard regs.<br /><br />Chris........

 

[tommays]

Re: Fuel pump,opinions wanted

this gives all the rules clearly and there are a lot but it is very easy to understand its 150 pages so give it some time<br /><br /> http://www.uscgboating.org/regulations/boatbuilder/downloads/fuelsystem.pdf <br /><br />tommays

 

[waterone1@aol.com]

Re: Fuel pump,opinions wanted

What achris said about needing checkvalves to make sure either pump is not "sucking air" or blowing the diaphragm out of the other pump is important. Coast Guard regs. say that the electic pump must only be operational when the key is in the start position or the engine is actually running(wired to an oil presure switch or other means to cut the pump off AUTOMATICALLY, if the engine fails,stalls or the fuel line ruptures). With that said the only easy way I see to be able to accomplish what you want while still keeping with the spirit of the coast guard reg. would be to connect the electric pump to a MOMENTARY push- button type switch (to be used for priming and emergency use only).

 

[Buttanic]

Re: Fuel pump,opinions wanted

I was going to wire through the ignition switch and oil pressure switch per the regulation. The only thing different will be the manual on/off switch so the pump will only run when I need it. <br />I also planed on valves to isolate the pumps.

 

[qystan]

Re: Fuel pump,opinions wanted

Buttanic<br /><br />You need a different switch, not the same low oil pressure switch that gives you the low pressure warning. That switch is closed circuited when there is no pressure = pump on when engine is not running.<br /><br />Looking at the 1998-2001 5.0 parts list, it shows another switch in addition to the low oil pressure warning switch (p/n 87-805605A1). <br /><br />Can't confirm if this is the switch you need, but this motor has the electric pump. You need to confirm with your source.<br /><br />P/N Serial numbers <br />87-864252A01 OM331443 and below <br />87-864252 OM331444 and up <br /><br />I think you'll find then interchangeable or superceded.