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Please review my fuel pump wiring diagram

Mercruiser Fuel pump PN 861155A3
#11 Mercruiser Fuel pump Oil pressure switch PN 87-864252A01
#12 Mercruiser Fitting for Fuel pump oil pressure switch PN 286241
#18 Mercruiser second fitting needed to install switch. 286241

No relay needed.
Do not install a momentary switch....
Power is supplied to the pump while cranking from the small terminal opposite the terminal that activates the starter. This set up is sufficient and factory.

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Mercruiser Fuel pump PN 861155A3
#11 Mercruiser Fuel pump Oil pressure switch PN 87-864252A01
#12 Mercruiser Fitting for Fuel pump oil pressure switch PN 286241
#18 Mercruiser second fitting needed to install switch. 286241
This is a prime example of how Mercury Marine indoctrinates their dealers and mechanics to sell OEM parts.
This is not a bad thing.... but for God's sake, when will you guys try thinking outside of the box once in a while?

No relay needed.
That may be true, but there is nothing that would prevent the safe use of a relay, as AFK mentions in his post #1.

Do not install a momentary switch....
There is nothing wrong with the use of a momentary switch in lieu of the Start-By-Pass circuit.
The start-by-pass circuit will operate the fuel pump automatically (during cranking), whereas the momentary switch would operate the pump via manual manipulation only.
The advantage would be the ability to prime the carburetor (this would after a duration of Non-Usage... as in a dry fuel bowl) without the starter motor being engaged.
If you do not see the advantage in that..... I'd suggest going back to school.


Power is supplied to the pump while cranking from the small terminal opposite the terminal that activates the starter.
Yes, that would be the "I" or "R" terminal..... No argument there.
I = ignition..... R = relay.

This set up is sufficient and is factory.
Post #1..... AFK's original 4.3L engine was equipped with a mechanical fuel pump.
The new engine will require an electric fuel pump.
This means that no matter what, he will now be either buying one, or making up his own wiring harness for his new electric fuel pump.




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Mercruiser Fuel pump PN 861155A3
#11 Mercruiser Fuel pump Oil pressure switch PN 87-864252A01
#12 Mercruiser Fitting for Fuel pump oil pressure switch PN 286241
#18 Mercruiser second fitting needed to install switch. 286241
This is a prime example of how Mercury Marine indoctrinates their dealers and mechanics to sell OEM parts.

This is not a bad thing.... but for God's sake, when will you guys try thinking outside of the box once in a while?

Thinking outside the box may be how you work but from a trained professional, a certified service center, Coastguard regulations and even an insurance company point of view, This is a back yard mechanic solution to a non existent problem and could cause real problems if not liability issues when the possible next owner seeks service. The seller will now become the boat manufacturer as he altered the EOM CG approved fuel system configuration


No relay needed.
That may be true, but there is nothing that would prevent the safe use of a relay, as AFK mentions in his post #1.

Do not install a momentary switch....
There is nothing wrong with the use of a momentary switch in lieu of the Start-By-Pass circuit.
The start-by-pass circuit will operate the fuel pump automatically (during cranking), whereas the momentary switch would operate the pump via manual manipulation only.
The advantage would be the ability to prime the carburetor (this would after a duration of Non-Usage... as in a dry fuel bowl) without the starter motor being engaged.
If you do not see the advantage in that..... I'd suggest going back to school.

If it was determined to be an effective and safe addition to an electric pump/carbed engine, OEM would have done so. They did not. I wonder why...........The key phrase to me is "BY-PASS" This means you are possibly doing something unsafe!

"
momentary switch in lieu of the Start-By-Pass circuit.".....................One in the same

Power is supplied to the pump while cranking from the small terminal opposite the terminal that activates the starter.
Yes, that would be the "I" or "R" terminal..... No argument there.
I = ignition..... R = relay.

Repeat from several posts

This set up is sufficient and is factory.
Post #1..... AFK's original 4.3L engine was equipped with a mechanical fuel pump.
The new engine will require an electric fuel pump.
This means that no matter what, he will now be either buying one, or making up his own wiring harness for his new electric fuel pump.

As recommended in an earlier post, Purchase the correct engine wire harness which will include all the correct wiring/connections for a electric fuel pump and needed components!
 
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Mercruiser Fuel pump PN 861155A3
#11 Mercruiser Fuel pump Oil pressure switch PN 87-864252A01
#12 Mercruiser Fitting for Fuel pump oil pressure switch PN 286241
#18 Mercruiser second fitting needed to install switch. 286241
This is a prime example of how Mercury Marine indoctrinates their dealers and mechanics to sell OEM parts.

This is not a bad thing.... but for God's sake, when will you guys try thinking outside of the box once in a while?

Thinking outside the box may be how you work but from a trained professional, a certified service center, Coastguard regulations and even an insurance company point of view, This is a back yard mechanic solution to a non existent problemand could cause real problems if not liability issues when the possible next owner seeks service. The seller will now become the boat manufacturer as he altered the EOM CG approved fuel system configuration
AFK will be adding the electric fuel pump (in compliance with USCG regs) along with the necessary electrical circuitry for the fuel pump.
It is his choice as to how he does it.
We are simply making suggestions to him.

No relay needed.
That may be true, but there is nothing that would prevent the safe use of a relay, as AFK mentions in his post #1.

Do not install a momentary switch....
There is nothing wrong with the use of a momentary switch in lieu of the Start-By-Pass circuit.
The start-by-pass circuit will operate the fuel pump automatically (during cranking), whereas the momentary switch would operate the pump via manual manipulation only.
The advantage would be the ability to prime the carburetor (this would after a duration of Non-Usage... as in a dry fuel bowl) without the starter motor being engaged.
If you do not see the advantage in that..... I'd suggest going back to school.

If it was determined to be an effective and safe addition to an electric pump/carbed engine, OEM would have done so. They did not. I wonder why...........The key phrase to me is "BY-PASS" This means you are possibly doing something unsafe!
The OEM may use a "start-by-pass" circuit that is triggered via the starter motor circuitry. Perhaps you are misinterpreting the words By-Pass.

The momentary switch system does not necessarily provide a by-pass.
Perhaps try to think of it as an over-ride to that of the N/O low oil pressure switch that would be used prior to cranking.


"
momentary switch in lieu of the Start-By-Pass circuit.".....................
One in the same
That is an ill informed and incorrect statement!

Power is supplied to the pump while cranking from the small terminal opposite the terminal that activates the starter.
Yes, that would be the "I" or "R" terminal..... No argument there.
I = ignition..... R = relay.

Repeat from several posts
And..........?

This set up is sufficient and is factory.
Post #1..... AFK's original 4.3L engine was equipped with a mechanical fuel pump.
The new engine will require an electric fuel pump.
This means that no matter what, he will now be either buying one, or making up his own wiring harness for his new electric fuel pump.

As recommended in an earlier post, Purchase the correct engine wire harness which will include all the correct wiring/connections for a electric fuel pump and needed components!
If that is what AFK wants to do, then of course that would be great.
Perhaps re-read post #1.


There is no need for any of us to continue disrupting AFK's thread with on going rude and argumentative rhetoric.
Play nicely, or don't play at all.

 
Do it by the OEM book. This is GASOLINE we are talking about, gasoline in a bathtub, which is an explosion hazard. FYI Rick most don't know this, If this man wires his boat according to your suggestions and someone gets hurt or dead, YOU will be responsible. There are things you just don't Backyard. This is one of them.
 
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