Automatic fuel pump wiring older Mercury

[Leedanger]

Hey Boys,

Have an older 50 hp Mercury that I can't seem to find a fuel pump kit for so I'm gonna install a low pressure electric. In the past I've just wired a switch on the dash but I'd like to step up my game to something more automatic. What I was thinking was still have a switch wired to the battery so to not draw from the ignition system, but then wire a relay that interrupts the feed when the key is turned off. U would then have to cycle the switch to start the boat again, but it wouldn't matter if u left the switch on. Any solid ideas on how to do this or better plans than that? Thanks!

 

[GA_Boater]

What's your serial number? You give up too easy, I know we have fuel pump kits for your motor. An electric pump is not a good idea.

 

[Leedanger]

1676632

 

[GA_Boater]

Right here - http://www.iboats.com/Fuel-Pump-Kit-18-7804-Sierra/dm/view_id.174937

 

[Silvertip]

You also need to cover the situation where engine dies but pump stays running!. Failure to do so can pump an engine full of fuel and when you try to restart you get the big "kaboom". I/O's do this through the oil pressure switch. Your engine doesn' t have one (or an equivalent).

 

[sam am I]

No Title

Might give this a shot if you HAVE to run electric.........


See H2O pressure trace in plot......I'd assume that your water pressure rise time and pressure upon the engine firing up would be close to this. When I made this plot, motor was just totally rebuilt, my idle was a little rough and dropping out a bit when coming off higher RPM's due to being out of tweek'n.....notice a few dips in H2O pressure below 5PSI

After you prime for a sec, then fire up, the H2O pressure comes up(looks less than 60 sec)the safety pressure switch switches over to the nc.contact will occur (just like oil setups). This wiring is essentially the same as 4 stokers cept the prime switch is the "s" terminal of the starter's solenoid .

If engine shuts off, pressure switch shuts off, fuel pump shuts off.... Rinse, lather, repeat.

5 PSI switch should do........Just don't crash and land dead on the primer's momentary pushbutton(or the key's start position on a car's ignition) switch with the key on


http://www.summitracing.com/parts/atx-os75/overview/

or

http://www.summitracing.com/search/p...9%2B4294823390

 

[Leedanger]

Right here - http://www.iboats.com/Fuel-Pump-Kit-18-7804-Sierra/dm/view_id.174937

I ordered this thank you.

 

[Leedanger]

Might give this a shot if you HAVE to run electric.........


See H2O pressure trace in plot......I'd assume that your water pressure rise time and pressure upon the engine firing up would be close to this. When I made this plot, motor was just totally rebuilt, my idle was a little rough and dropping out a bit when coming off higher RPM's due to being out of tweek'n.....notice a few dips in H2O pressure below 5PSI

After you prime for a sec, then fire up, the H2O pressure comes up(looks less than 60 sec)the safety pressure switch switches over to the nc.contact will occur (just like oil setups). This wiring is essentially the same as 4 stokers cept the prime switch is the "s" terminal of the starter's solenoid .

If engine shuts off, pressure switch shuts off, fuel pump shuts off.... Rinse, lather, repeat.

5 PSI switch should do........Just don't crash and land dead on the primer's momentary pushbutton(or the key's start position on a car's ignition) switch with the key on


http://www.summitracing.com/parts/atx-os75/overview/

or

http://www.summitracing.com/search/p...9%2B4294823390

This is cool, I like the idea. I worry about frequency pulsing back into the ignition system. Maybe Im reading your schematic wrong or not seeing something that would protect it. What about this though.... instead of (batt -> ign sw -> primer -> pr sw -> pump) you go ( batt -> dash board sw -> primer -> pr sw -> pump) hopefully that is discernible, but basically just use a dash board switch instead of the ignition switch. Still using water pressure as the means of a safety switch and mom on button for prime. It also adds a little protection towards impeller abuse.

Lastly thanks to all that replied. I do understand the inherent risk of using an electric fuel pump on an outboard and that is why I will be rebuilding the mechanical instead on this motor thanks to GA.

 

[sam am I]

No Title

Sure, a few ways to get there from here and i get what you're saying(except the impeller thing, with key to "on", push prime for 5 sec, turn to "start"......VEEEROOoooM. "Abuse"?).

I personally would( and if I HAD to do this) use the ig. signal to inhibit to entire works as I had above.

My thoughts were....If you left the panel switch "on" inadvertently(probable) , there is a chance(very slight) that the prime could be pushed (the dog's butt!!)and fuel the motor when not wanting too. With the ig. signal, the key would have to be 1) Inserted, 2) be turned to "on"(dog's don't have thumbs) and then 3) use the dog's butt to push the prime button.... Which is more of a certainty of someone wanting to start up the engine.

And although the ig. signal is directly derived from the batt. certainly we could do something like this and isolate ignition component's power and still use the ig. signal to inhibit the overall functionality ....


Side note I thought of when i was pondering this........NO MORE PRIMER BULB PUMPING, Yipeee!!!


Moot point though, best go with rebuilding.....GL.

 

[Silvertip]

Wouldn't a $4.59 fuel pump kit be a whole bunch simpler, just as reliable if not "more" reliable, much safer, and result in a fewer number of potential points of failure.?

 

[sam am I]

Wouldn't even of had to question it!!