Fuel Supply Line on 3GM30F

[Steverhnm]

I have never been able to figure out the line size for the fuel supply and I can't get to my boat, it's in Mexico. I want to get some new hose and add some plumbing to make it easy to change the Racor filter. Does anyone know the size and type of fuel line I should be using for a stock setup? Last time I was down there I went to check the hose clamps and most of them crumbled in my hands, I was amazed I did not have fuel supply problems.

Also, is there a return line for the fuel to the tank? I have seen what I think might be a return line but have not chased it through the bulkheads. I will if someone tells me there is a return line and it makes sense.

The PO put an electric fuel pump just before the Racor filter. If there is a return line I was thinking of adding a fuel shutoff valve before the Racor, and adding a couple of T's to connect the engine side of the filter to the return line so that when I change the filter I can bleed any air out back into the tank, not disturbing the engine. Change the Racor more often and leave the primary alone. It would also allow me to maybe "polish" my fuel a little or at least get rid of any water if I get some, a common even in Mexico.

Thanks, appreciate the help.

 

[kloudie1]

I don't remember the size, but yes, there is a return line back to the tank. That probably should be changed as well. It is the rubber line that leaves the aft top injector on the engine.

 

[Allan12210]

I don't remember the size, but yes, there is a return line back to the tank. That probably should be changed as well. It is the rubber line that leaves the aft top injector on the engine.

Mine started life at 1/4". I upsized later to 3/8". Considering the consumption by the engine, the return is still 1/4". I've never touched the return line on mine.

Regarding polishing, I was told once that the stock mechanical lift pump pulls from the tank about 3 times the volume of the actual consumption. For my 3GMF22, I use about 0,6 gallons/hour (or .01 gallons/minute), so 1.2 gallons/hour (.02 gallons/minute) would return to the tank. Recirculating with the stock pump doesn't sound very efficient. I don't know how much more the electric pump can move, but imagine the limiting factor becomes that hose size, and the flow rate is still close to stock. Even with perfect mixing of the return stream back into the tank, a rule of thumb has always been that it takes 6 complete turnovers of the volume of the tank to pass all the contents through the filter at least once. For my 21 gallon tank that would be 105 hours to completely filter the contents. But at the burn rate of 0.6 gph, I would use all the fuel up in 35 hours. Then it would be 100% filtered. So, for a polishing setup, I would think a separate system would make more sense. Something like 126 gph (2.1 gpm) to polish 21 gallons in an hour (reasonable cleanup time). Scale accordingly for larger capacity. This would require bigger lines and a bigger Racor. Concerning water, since it settles to the bottom and would be mostly picked up first no matter how full the tank is, it might be good to have two Racors that could be switched quickly if a large slug of water were introduced on fueling to avoid overwhelming the system. With an electric fuel pump, it should push air out through a bleed screw pretty well without introducing more complicated plumbing that could result in more air leaking into the system. Sort of creating a problem it is supposed to fix.

 

[splax]

The electric pump I got moves about 30 gallons per hour, so my tank volume is cycled 3 times every 2 hours. From what I understand of what is described, it seems that a "T" after the electric pump with the line going to a filter then to a "T" into the return line might be smart.
As far as upsizing the line, I think it is 1/8" metal tube after the lift pump to the injector pump, so 1/4" fuel line from the tank is more than sufficient.

 

[kloudie1]

Yup.. I think mine is 1/4" but I didn't want to mislead.. The reason I mentioned the return line replacement is that when I replaced the supply side a few years ago, I didn't change the other.. yes, ya guessed it, about 18 months later, the return line cracked where it runs on top of the tank of the 34.. a stinky mess it made. since it was 28 or so years old, I think I'd gotten my money's worth out of it.. and it would have been better to make only one trip into the pit to change both..

 

[H3newdog]

I'm just about to redo my entire fuel system. The PO had installed two filters with two valves so you could change from one to the other and replace the out of service one with the engine in use. Nice set up except it was next to the shaft log and absolutely impossible to service and if you knew where to put your hands you might be able to turn both valves as you could only see the one.
Anyway, the line from my tank is 3/8" (Westerbeke 21) but the lines in and out of the filters along with the return line to the tank are 5/16". I don't know if this was done on purpose or by two different guys. But hey when I'm done it should be 3/8" all the way as the inline pump I plan on using for a backup and for polishing is 3/8" as well.
As I understand the original fuel pump on the 21 (mine looks original) is a very good unit. Anyone have any history or advise. When I got the boat there was an issue that cleared up by bypassing the engine mounted fuel pump but still using the engine mounted fuel filter so I suspect the pump may be weak.

 

[H3newdog]

The PO put an electric fuel pump just before the Racor filter.

I learned that the filters I have (Parker/Raycor R201) are only to be used in the supply side line before the pump. Something that I never would have thought of. You might want to check the type of filter to be sure the PO didn't miss the memo.

 

[Steverhnm]

They are supply side... thanks