Marine EFI fuel routing

[roughneck427]

This is crude picture of the fuel system on my boat. It is not a factroty deal by any means. I put a FP gauge on it and at idle and WOT it maintains 43.5 psi. Ive never seen anything dump back into the suction side any thoughts on this or should i buy these?? http://www.jegs.com/i/Moroso/710/65385/10002/-1


I would have to have another T for the tanks or run ball valves and switch from tank to tank.

[EagleMark]

Dual tanks, feed and returns sure add up to very complicated and expensive fuel plumbing. Plus all the extra lines and fittings to leak!!! Fuel leaks are always a worry to me in conversions. But in boats it's enough to cause anxiety that needs medication!

There are some factory Coast Guard Approved dual tank switches but WOW are they costly!

If your maintaining pressure then I'd call it a blessing and leave it alone.

[roughneck427]

Yeah it looked like a hillbilly setup but the clear fuel filter showed no bubbles or anything i just never thought of it that way and yes i agree about the lines especillay in a boat.

[steveo]

i never see return line systems to the tanks in the marine world, except for diesel... and i dont see anything wrong with your tee'd in return line. looks good.

you should run two ball valves on each inlet of a 2 in 2 out water seperator right before the pump (preferrably w/ a racor filter), a good water seperator is a pretty good flow equalizer too.

if you find one tank draining too fast you can close the ball valve on it slightly... or you can alternate tanks. no big deal.

[roughneck427]

Ok thanks guys i know its running fat and when i start it it has a high idle for minute before it idles down i havent used tunerpro that much or scanner pro so ill be asking questions. Ill be using MEFI burn with a LC1 wideband with the innovate exhaust clamp on it no water running through headers temporarly to dial it in. Anyone here tune a MEFI here i know in he other thread i kinda hijacked on someone mentioned all bpw setting and no VE??

[1project2many]

My Mercruiser system uses an engine mounted, low pressure mechanical pump to supply fuel to a reservoir. The reservoir contains the high pressure pump for the rails. The regulator is installed on the rails and unused fuel is returned to the reservoir. A float valve in the reservoir limited low pressure fuel flow to match demand. The system works but there's no way to cool the fuel if it gets warm. There is a vapor vent however. If your system gets warm and produces fuel vapor where will the vapor go? Maybe you could install 3/16" tubing as a vent to the tank just in case?

Marine systems tend to run rich ime. Water cooled exhaust temp must be kept low and I believe the systems are tuned rich to help this.

[mmigacz]

i never see return line systems to the tanks in the marine world, except for diesel... and i dont see anything wrong with your tee'd in return line. looks good.

you should run two ball valves on each inlet of a 2 in 2 out water seperator right before the pump (preferrably w/ a racor filter), a good water seperator is a pretty good flow equalizer too.

if you find one tank draining too fast you can close the ball valve on it slightly... or you can alternate tanks. no big deal.

Do you know why they don't use return lines to the tank on marine systems?

[1BadAction]

Do you know why they don't use return lines to the tank on marine systems?

The coast guard does not like fuel being pumped at high pressure, and they don't like it being pumped back into the hull. There are required failsafes on race boats running return systems but rec boats with high perf engines run the gamut from relatively safe to "holy shit I'm not getting into that thing with you". lol There are dual tank/dual return setups out there, but they generally are on twin engine hulls. The real fun is trips, where the right and left draw from each tank, and the center motor draws from both.

Here's a primer on EFI in the high perf world. http://www.diamondmarine.com/web_pag...l%20System.htm You can get away with different hardware and added valves and such with a less hp/cube 4 stroke but the basics are the same.

[roughneck427]

Well learning some stuff about these mefi controllers I had a high idle and raw fuel was popping in the exhaust. I grounded the timing test wire and found the timing was off 20degrees I locked it in at 8 per specs and adjusted the throttle blade tps reading .65v idle trimmed out nice and has a cool little lope to it. I received mefi burn Bob helped my unlock the controller and read out my tune I think I have a lot left in this thing check out the spark tables.

[sammy2009]

I just completed my twin engine conversion and launched the boat today. Have to say the engines start much better but I'm troubleshooting an idle issue. here is a pic of my starboard engine. I was able to run a return line to the tank. I was lucky my tanks had 2 pickups each and a spot for returns.IMG_20140504_164646204_HDR.jpg