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Old 05-17-2019, 07:04 AM   #1
City: Stamford
Vessel Model: Mainship 34
Join Date: Nov 2018
Posts: 1
Gen Fuel Return

Late last fall I picked up a 1980 Mainship 34. It has the standard Perkins Diesel and a northern lights gen (m673D). Two new fuel tanks. The prior owner explained to me at the time that the Perkins draws from the Starboard tank, and he uses the generator to move fuel in between by directing the fuel return with a couple valves.

1) This doesn’t seem like a practical setup, but I don’t know enough. Anyone seen this before?
2) How much fuel would the gen return? In other words, any idea at what rate the fuel would move between tanks. E.g 3gph or 15gph.

Apologize if these are dumb questions, new to the trawler/ diesel game trying to learn.

I sent the prior owner an email, hoping to catch with him today or tomorrow.

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Old 05-17-2019, 07:21 AM   #2
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City: Slicker?
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Welcome aboard.

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Old 05-17-2019, 07:27 AM   #3
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City: Wilmington, NC
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
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I don't know the exact return fuel rate, but have run a bunch of those 643 and 673's in my shop. Return is just a slow dribble. I'd guess about one or two gph. Not appropriate for transferring fuel.

Normal is for main engine to be switchable between tanks. It's pretty common practice for gennie to be on only one tank as it is not critical for navigation.

Can you replumb the lines so main engine goes through the switching manifold?

Is there a cross-over line tying the tank bottoms together?
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Old 05-17-2019, 07:32 AM   #4
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City: Fort Myers, FL... Summers in Crisfield, MD
Vessel Name: Slow Hand
Vessel Model: Cherubini Independence 45
Join Date: Dec 2010
Posts: 10,122
While it would certainly work, whether it would be adequate for its purpose would depend on how much you run the generator. I think a purpose built fuel transfer / polishing system is a far better option. If you need to move 30 gallons of fuel to trim the boat, I'd rather do it in 10 minutes as opposed to hours.

I'm tired of fast moves, I've got a slow groove, on my mind.....
I want to spend some time, Not come and go in a heated rush.....
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Old 05-17-2019, 09:05 AM   #5
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Join Date: Jan 2010
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I don't know the actual flow rate but my westerbeke 8 BTD return sub substantial amount of fuel to the fuel tank
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Old 05-17-2019, 11:35 AM   #6
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City: Kiln,MS
Join Date: May 2016
Posts: 457
you will need o call NL and find out how what the lift pump gpm is. or do a timed volume test with a 5 gal bucket. i can't see it being a timely process and to easy to forget about it. imo a dedicated pump that moves a good gpm would be better. properly connected you could also use it for a priming up and back up lift pump for any of the engines.

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diesel engine, fuel return line, generator

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