Connected Fuel Tanks?

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WashingtonMike
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Connected Fuel Tanks?

Post by WashingtonMike »

I have two 120 gal diesel tanks under the aft cabin bunk. It's on a 1981 duel cabin 37. I'm having fuel gauge issues. They both show full appropriately but then they both suddenly drop to around a quarter or 3/8 full when they should be at 3/4 or higher.
I have two questions:
Wondering if these tanks are connected or are Marinettes usually set up as one tank per engine?
Is this problem likely the fuel gauge sensors or something else?

Thanks for any thoughts on this. To be safe, I keep filling up when don't need it.
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GB49
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Re: Connected Fuel Tanks?

Post by GB49 »

Marinette used a crossover with the dual tank setup. You could run each tank independently, both or only 1 at a time depending on the valve config.

If the senders are original they may be worn out especially if there is/was water in the tank.

Check the wiring at the tanks and at the gauges. I have found the ground wires from tanks to the hull can get corroded as well as the wire from the sending unit to the back of the gauge. Some connections may be spade and some are brass threaded.
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WashingtonMike
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Re: Connected Fuel Tanks?

Post by WashingtonMike »

Thanks for that. That sounds like good advice! I'll check the ground and wiring at both ends.

I thought a crossover was used on most boats of this size. The problem is, the tanks are right next to each other with about an inch between them. There are no valves that I can see. I assume they would be on the bottom but that's not accessible without tearing out some structure. These tanks may have been installed later but I'm not sure. The engines were converted to diesel around '94 so maybe the tanks were also switched out.
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bill
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Re: Connected Fuel Tanks?

Post by bill »

BigM
The cross over valves on my 37' are located by the fuel strainers/filters in the engine compartment. ;)
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jralbert
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Re: Connected Fuel Tanks?

Post by jralbert »

If this isn't too simplistic, trace your fuel lines back to the tanks. Guessing that when the switch to diesel took place, there was no reason to eliminate the crossovers.
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WashingtonMike
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Re: Connected Fuel Tanks?

Post by WashingtonMike »

This all makes sense. Thanks so much for the input. I'm in Alaska right now but headed to the boat in January, (in Washington State). Can't wait to resolve this and you're right, it does look pretty simple. I'll check out the wiring to the fuel gauges, sending units and locate the tank valves. I just assumed they would be next to the tanks, not in the engine room. I'll trace the fuel lines to wherever they lead.

By the way, I may have one of the few Marinettes in the Pacific Northwest. It sure is a head turner since nobody knows what it is.

Mike
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Busia
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Re: Connected Fuel Tanks?

Post by Busia »

I know there was a Marinette in Valdez, one in Anchorage, and I have one in Ketchikan.
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