converting Merc454s to electric fuel pumps

F

footloose

Member
Joined
Dec 10, 2001
RO Number
6963
Messages
619
Hello all -

Looking to upgrade to electric fuel pumps on my 90's carbed Mercruiser 454s- tired of 5 minute crankup times.

4 tanks are far forward and deep (below engines) plus I run two sets of fuel/water seps to keep crud outta the engines.

Thinking of replacing the mechanical pumps with block-off plates, wiring in Carter 4070 pumps which can handle up to 70gph.....hope I never need that!

Could use recommendations on which model Carters if 4070 is not best, any hints on wiring and any other things to be careful off?

Had a mechanic tell me to mount 4070 to same block off plate so no new fuel lines to run....and connect to an oil pressure switch so if oil PSI lost they cut off. Does this make sense?

Thanks!

O
 
Good to see you back on board Olivier!
 
Had one installed when I bought a '73 with two aux tanks. Main tank went dry and too much air in the aux lines. Flipped a switch, it sucked fuel up and pumped fuel to the mechanical pump and I switched off the elec pump. Pump had free flow-thru and it was always connected in-line between the 4 way switch and the mechanical pump and never interfered with normal operation. No need to remove mechanical pump.
 
I was going to suggest the same thing. We have priming pumps on our diesels. What they did was insert them into the line but they T'd in an another line around them with a check valve so the fuel had to go to the engines. The important thing is to ensure the pump is rated for gasoline.
 
quote:
Originally posted by jtybt15

Had one installed when I bought a '73 with two aux tanks. Main tank went dry and too much air in the aux lines. Flipped a switch, it sucked fuel up and pumped fuel to the mechanical pump and I switched off the elec pump. Pump had free flow-thru and it was always connected in-line between the 4 way switch and the mechanical pump and never interfered with normal operation. No need to remove mechanical pump.

Click to expand...


Thanks Charlie - any idea what model and number of the pump was? Foot
 
Couple words of caution...

Big difference between electric pumps for carbs vs. fuel injection. Your carbs will only take a few pounds of pressure before it overwhelms the float valve/needle and causes a flooding issue.

OE electric fuel pumps are also wired to the oil pressure sensor. If the engine dies, or a fuel line breaks (causing the engine to die), the fuel pump shuts off automatically when your oil pressure drops. If you simply wire the pump so it's on when the ignition is, you run the risk of pumping raw fuel into the boat.

If you're gonna use one, I'd vote for setting it up as a manually controlled transfer pump between tanks, rather than as a direct feed to the carbs. Fuel handling on a boat isn't a good place to try redneck engineering.

My .02

My .02
 
That's a great point, and even if the pump had a built in cut off, I would add in that feature.
 
Thanks B.

Between work and my baby getting married it has been a very busy year - other than night rides we have been unable to boat much....but that will change now. Foot

quote:
Originally posted by jtybt15

Had one installed when I bought a '73 with two aux tanks. Main tank went dry and too much air in the aux lines. Flipped a switch, it sucked fuel up and pumped fuel to the mechanical pump and I switched off the elec pump. Pump had free flow-thru and it was always connected in-line between the 4 way switch and the mechanical pump and never interfered with normal operation. No need to remove mechanical pump.

Click to expand...
 
The more I think about this the more I like the idea of simple fuel primer pumps - flow through. If anyone knows what model number would really be helpful.
Thanks!
Foot
 
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