Re: [OMC-Boats] Fuel Pump Woes

Bill, I would agree with Ethan's excellent write up.

I would only add that using a old "on-hand" part is ONLY "okay" for troubleshooting.

Personally I would recommend a new "known quantity" marine-rated pump. You can lookup the original fuel pump PSI spec in the OMC/Selog manual, think it was ~ 4 - 7 PSI (?) Flow capacity (Gallons per Hr) won't a concern in your application. Also, be sure and FUSE-PROTECT this new circuit appropriately. A new pump should come with full installation instructions.

Removing the old mechanical pump and replacing with a block-off plate will also gain you a little less parasitic drag on the engine, resulting in marginal power and economy gains, but placing more reliance on the soundness of your electrical system. You also see this done with electric water pumps on high performance applications.

-----Original Message-----
From: omc-boats-bounces@... [mailto:omc-boats-bounces@...ultimate.com] On Behalf Of Ethan Brodsky
Sent: Tuesday, June 01, 2010 10:48 AM
To: BLDFW
Cc: omc-boats@...
Subject: Re: [OMC-Boats] Fuel Pump Woes

For what it's worth, I've been running an automotive fuel pump (I think it's a Holley red) for as long as I've had the boat - it was installed by a previous owner. The plumbing is tank, fuel shutoff valve, fuel filter, pump, and then straight to the carb. It's wired into the key switch - it comes on when the key is in the "Run" position (or "Accessory", which has always annoyed me). I know you're supposed to use marine pumps only, but the pump failing and leaking externally is pretty far down on my list of concerns.

Just make sure your pump is designed for carbureted engines and rated for the proper pressure (a few psi?). My engine has a "blanking plate" over the spot where the original pump mounted - you could maybe leave the old broken pump in place, but it might eventually overheat and seize without fuel to cool it - I'm guessing the plates are pretty easy fo find.

My opinion for the "best practice" for wiring up electric fuel pumps on non-computer-controlled engines is to put them through a switch that's driven off the oil pressure sensor. So the pump only turns in two circumstances - when there's oil pressure, or when the key is in the "start" position. It's a cheap way to protect your engine in case you ever lose oil pressure, and it avoids running the pump when the engine isn't running. It might be tricky to wire that up though with the grounded-when-there-is-no-oil-pressure switch that's used in these engines
- you'd need some clever setup with some resistors, a transistor, and a relay... Er, or you could just buy the Sierra part:
   http://www.marineengine.com/parts/sierra_catalog/80240033.pdf
(OP22900 would work, I'm guessing, though maybe the 22891 would be a better choice). This might require finding another spot to plug in an oil pressure sensor though, or installing a T, so it might be complicated.

Ethan

On Mon, 31 May 2010, BLDFW wrote:

> Alas, on my maiden voyage of the 2010 summer season with my newly
> fabricated and installed side guides I never made it away from the
> boat ramp.  While I had a couple of successful runs late last year,
> this year the fuel pump crapped out before I could get her away from
> the ramp.  It would not pull from the full tank.
>
> Question.....
> I have a spare electric fuel pump I can use to bypass the old
> mechanical one.  I know someone will say it so I'm going to
> inquire.....What's the con of using it on my boat??  If I were to use
> it, is there a best practice method of hooking it up aside from the ignition key source?
>
> Thanks.
>
> -Bill
> Dallas, TX
> 1970 Evinrude Explorer - 155 Buick V6 - OMC Sterndrive
> http://www.photobucket.com/evinrude_explorer
>
>
> PS...the guides worked really really well when we floated it back onto
> the trailer.  Looking forward to doing it under power!
>
>

--
<a href="http://homepages.cae.wisc.edu/~brodskye/"> Ethan Brodsky </a>