mech. pump, electric in series?

[ArtJ]

A gear head boating friend said that often in cars people use both mechanical
and electric pumps in series as backups to each other.

What do you guys think of this idea? will it work?


Regards

Art

[Dave Neptune]

2 pumps

Art, yes it is true that many hot-rods are equiped with an electric pump feeding the mechanicle one. This is usually due to the fact that they are using the wrong pump for there HP rating and just added on hoping to make it work. Until you are building an engine in access of 1000 HP the correct single pump will work fine. Having a back up pump ready to go is a good idea if you are offshore and a pump fails. Then you INSTALL the back-up pump and get back on your merry way.
The problem with the A-4 is finding a small enough electric so as to not have problems feeding it. All we require is about 2~3 psi and 2 GPH which would make just over 30 HP, when our A-4's are making about 24~25 @2500 rpm.
I cruise at 2000 RPM and am making about 20 HP using the Indigo prop.
It would be overkill. I do carry an electric for back up and have yet to use it in the 15 years it has been aboard. I bought it when I couldn't get fuel preassure once and that I later found out was a crack in my Racor.

Dave Neptune

[ArtJ]

The reason I am interested is because of shutdowns during trips, sometimes
in a very dangerous spot (near rocks in Maine or a tight passage). My hope would be that
the second pump would permit continued operation, as opposed to shutting
down and letting the engine cool down, bleeding carb etc.

Hopefully, this would overcome potential problems due to electric pump
failure or loss of prime. We have discussed vapor lock the engine
on the Tartan 34C is in a very hot, cabin located, small box. Also, when the tank is down to half
I am wondering if it could suck air pitching in rough seas.

The alternative I was thinking of was going back to a straight mechanical
pump, because I have had poor experiences with the Electric pump.

Regards and thanks

[Dave Neptune]

Hmm!

artj, if you are having fuel related shut downs it is time to replace the pump. The stock mechanicle or the replacement electrics should give you years of RELIABLE service. I rebuilt my mechanicle pump 16 years ago and have not had a fuel delivery poroblem other than filter related, once.
However I am thinking that I may just rebuild it again this coming season for piece of mind.

Dave Neptune

[ArtJ]

Hi Dave

I have just replaced the electric pump with a new facet pump so far
it is working, but only used a week or so before hauling out.

I have also rebuilt the old mechanical pump as a backup. I have not
used the mechanical pump for over 12 seasons, but will replace the
electric pump with it if shutdowns continue. I don't want to beat
a dead horse with my shutdown issues which have been posted elsewhere

was just interested if I could improve my odds of shutdown prevention
by using both pumps.

I also cannot test anything out until at least mid May
since the boat is winterized in Boston.

Regards


Art

[ArtJ]

By the way, I noticed a small round filter sitting inside the sediment bowl
on the mechanical pump. It didn't connect to anything else.
I mentioned
it to Ken, he said to discard it. Has anyone seen this filter before?


Regards

Art

[Al Schober]

That 'sediment bowl' on the stock mechanical pump is the primary weakness of the pump. It's very subject to leaks due to the poor seal integrity of the bowl, and the susceptability of the bail/screw system to corrosion. The pump could be much improved if the bowl could be cut off and fuel fed directly into the pump.
The 'pump' portion of the pump is fine - subject to wear and old age, but quite repairable. If it weren't for that bowl thing, I'd still have one.

[Dave Neptune]

The Bowl

Yes the sediment bowl can be trouble, but if it is accessable it works quite well. Since going with a Racor I removed the sediment filter put in a screen and "sealed" the bowl with Av grd. It's been fine for quite a while. A little preventive manitenance goes a long way, I spray the outside of the engine with WD-40 and wipe it down every second or third trip. Keeps the rust away and all the exterior screws work.

Dave Neptune

[sastanley]

Dave...fascinating...you are right...the bowl is likely unnecessary with the modern filtration systems most of us are using.

I am about to rebuild my current 'backup pump' so it is ready to go as a spare...maybe I can fabricate some bypass for the dreaded bowl!

[Dave Neptune]

My trick

Shawn, I cut a gasket and used Av grd to seal the bowl. I have not needed to check it since (at least 10 years) and it doesn't leak a bit. I wanted to pout a screen in it but decided to leave it out. Between the Racor and the inline @ the carb I have had no fuel issues.

I just pulled my carb to do some tinkering and I found that I am now being bit by the Ethenol bug. The inside was a bit on the green side. I'll be draining the bottom of my tank this weekend before I head out to try the tinker and do a bit of sailing.

Dave Neptune

[ArtJ]

[QUOTE=Dave Neptune;29574]Yes the sediment bowl can be trouble, but if it is accessable it works quite well. Since going with a Racor I removed the sediment filter put in a screen and "sealed" the bowl with Av grd. It's been fine for quite a while. A little preventive manitenance goes a long way, I spray the outside of the engine with WD-40 and wipe it down every second or third trip. Keeps the rust away and all the exterior screws work.

Dave Neptune[/QU

Hi Dave

Could you describe the filter that sits in the bowl and how it was supposed
to work? The one that was in my bowl looked like a miniature car air cleaner
or lawn mower air cleaner. Also where are they available?

Thanks

[sastanley]

Dave, I need some help...what is 'Av grd'?

Art, that sounds to me like some aftermarket filter for an entirely different application that someone discovered would 'fit' in the sediment bowl. Since the fuel comes in the side, thru the sediment screen, into the bowl, (water would then in theory separate and drop to the bottom of the bowl) and the good fuel would rise and go up thru the center of the chamber then off to the carb, maybe that filter would fit snugly up on that center chamber to keep debris and water from exiting the sediment bowl.

[ndutton]

Dave, I need some help...what is 'Av grd'?

Of course, Dave should be the one to say but I'll make a guess he's talking about aviation grade Permatex.

[Dave Neptune]

Oops

Niel gets the prize. Sorry Shawn, but it did work like a charm. Also Fram does make filters that fit and function perfectly. I don't remember the number however it is the same as there small 1/8 inline filter separator. I've used them on many small outboards up to a 100HP. They probably supplied the original for the A-4 pumps anyway.

Dave Neptune

[ArtJ]

Thanks guys

Do you think that using a in line polishing filter between the carb and pump
eliminates the need for the sediment bowl filter?