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Mercruiser 4.3 fuel pump need advice

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drago007

New member
Hi guys , I'm new in boating and in this forum,so need some advices...
My first boat is with 1991 Mercruiser 4.3 LX engine,and I bought it with overheated engine. Now I have installed new engine (block with heads), but the new block is without the hole for fuel pump, so I bought Facet brand electric fuel pump. The questions is:

1. The best and simplest way to wiring the pump?

2. In the carburetor (Rochester 4 BBL) beside the main fuel inlet pipe there is small brass union, which previously was connected to the mechanical fuel pump with transparent hose. So where now I should connect this hose?
Thanks !
 
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using an electric pump makes the hose obsolete now, did you install the pump with the oil pressure switch? Some electric pumps can draw a bit too much current for the pressure switch and burn it out. I install electric pumps using the small cube relay to sense oil pressure and activate the fuel pump.
 
Most of the newer boats have the main power and the alt output connected to the 90A fuse link at the starter. I had 2 customers smoke their alt and lost power to everything because the 90a blew.
To regain power and avoid a costly tow remove the alt output wire by removing or cutting, unplug the sense and excite plug and insulate the orange wire.
Take your long 14Ga jumper(you do carry one right) and connect to the + battery and the red/purple wire at the 50A circuit breaker. This will restore engine system power to get
back to port. And when making the repair, remove the system power wire and connect direct to the startrs battery post. Its still protected by the 50 a circuit breaker and doesn't need a 90A ahead of it.

[IMG]http://i57.photobucket.com/albums/g219/BtDoctur/UntitledB4_zpsffefyqkg.jpg
Most of the cube relays used are the same ones used in the Chevy Blazer. same plugs for the coil ,dist, fuel injection , sensors, the 3 fuses under the metal lit, etc.
Also the plugs for the relays have the same color code incase you have a bad contact.
So if you wanted to have a relay power the electric fuel pump instead of the pressure switch that burns out visit your local junk yard. this way the relay contacts will power the pump and the relay is operated by the pressure switch.
 
Thank you for your posts...
I only got the engine in and no fuel pump been connected yet...
I'll have in mind your suggestions about alternator...
The only thing my boat hasn't got the 90A fuse... (Or I can't find or maybe you do know location of it so I can check it out)...

I do understand that that brass union won't be used anymore but what I am trying to find out what was it been used before...

One more question I have about oil pressure switch where should I install the switch to the block, because the actual hole already being used by oil pressure sensor...
 
what you are referring to as a union is really an adaptor - hose barb on one end and pipe thread on the carb end. It's purpose is to provide a termination for the sight tube, from the fuel pump. the sight tube's purpose is to delivery fuel into the carb in the event that the (no longer used) mechanical fuel pump's diaphragm fails...just put a pipe plug in the carb's NPT-threaded hole...
 
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