Fuel Gauge - 2001 Mainship 34 Pilot

[LakeErieWX]

We are new owners of a 2001 Mainship 34 Pilot. After sailing for more than 30 years, this is our first powerboat. We have a single engine and two 125 gallon fuel tanks. Each tank has a fuel sending unit, but there is only one fuel gauge at the helm. There is no option on the gauge to switch between tanks, so what level is the gauge displaying?

Thanks,
Mark

 

[rgano]

It is probably set up like my 30 Pilot II was when I bought it nine years ago with level sensors in both tanks but only one connected to the fuel gauge. You need to find the sensor on the top of each tank to see which one has a wire connected. I ended up running a wire to the helm from the originally idle sender of my stbd tank and connected it and the wire coming up from the port tank to a double throw toggle next to the console gauge. The center wire of the toggle was run to the gauge. Here is the toggle labeled with port and stbd tanks sensing over the top of the cluster gauge.

 

[Mainship Pilot]

Rich, You have some nice upgrades there on your panel! I like the Start/House voltage switch. Are the Start and Thruster banks combined in that switch, or is the thruster bank, just not listed there? Or is there a parallel to bring in the thrust bank if need to start? That window wash button is a bit sketchy though, I think it's actually connected to an ejector seat!

 

[rgano]

Yeah, Bill, you gotta watch pressing that red button!

The battery select switch simply allows me a digital method of checking the two banks' voltages.

Start and thruster banks are one and the same, my two Odyssey 34 PC1500 start bank AGM batteries joined in parallel. My house bank of two Optima yellow tops is normally separated from the start bank except for a Blueseas ACR and a manual paralleling switch in the engine compartment which I have only ever switched on once when the starter batteries were too depleted to start the main engine.

 

[Mainship Pilot]

Yeah, Bill, you gotta watch pressing that red button!

The battery select switch simply allows me a digital method of checking the two banks' voltages.

Start and thruster banks are one and the same, my two Odyssey 34 PC1500 start bank AGM batteries joined in parallel. My house bank of two Optima yellow tops is normally separated from the start bank except for a Blueseas ACR and a manual paralleling switch in the engine compartment which I have only ever switched on once when the starter batteries were too depleted to start the main engine.

Gotcha, My Start and thruster banks are separate since I have bow and stern thrusters, 2/6v for the thruster bank and group 31 for the start, these all came with the boat when I bought it, and still holding strong, so no reason to change them out until I have a reason! As you know my house is 2 T-165 6V's, with a Renogy solar system tied in, before the Xantrax. My parallel switch is a set of jumper cables! It's on the list........

 

[Mainship Pilot]

Another question, why do you have a stbd and port tank switch, since there is a crossover line to both tanks, they will be relatively close.......I realize you have a NexGen 3.5, but the difference still should be negligible, No??

 

[LakeErieWX]

It is probably set up like my 30 Pilot II was when I bought it nine years ago with level sensors in both tanks but only one connected to the fuel gauge. You need to find the sensor on the top of each tank to see which one has a wire connected. I ended up running a wire to the helm from the originally idle sender of my stbd tank and connected it and the wire coming up from the port tank to a double throw toggle next to the console gauge. The center wire of the toggle was run to the gauge. Here is the toggle labeled with port and stbd tanks sensing over the top of the cluster gauge.

View attachment 154799

Rich,

Thanks, your post is a big help. I must admit that while I noticed that both tanks have a sending unit, I can't confirm that the starboard tank is wired.

Mark

 

[mncruiser]

As others mentioned, check to see if you have a crossover line between port and starboard tanks, I'd be shocked if you did not, and very little reason to not have the crossover open between sides unless there is a problem.

On our 2001 390, fuel draw for main and generator is from starboard, and the fuel return from the main goes to the port tank. If you had full tanks and ran the boat, you could potentially overflow the port side tanks ifthe crossover was not open.

 

[LakeErieWX]

I checked the tanks, and the sending unit on the port tank is not connected to the gauge. The valves to the crossover hoses are open so the sending unit on the starboard tank should provide a reading for both tanks. However, we haven't purchased fuel yet and I have been wondering how you know when both tanks are fuel if the gauge is only showing one tank. The flow within the crossover hoses is much slower than the fill rate from the fuel fill and would therefore be inaccurate during fueling. I'm going to follow Rich's suggestion and wire a A-B switch in order to switch the gauge from one tank to the other.

 

[mncruiser]

I checked the tanks, and the sending unit on the port tank is not connected to the gauge. The valves to the crossover hoses are open so the sending unit on the starboard tank should provide a reading for both tanks. However, we haven't purchased fuel yet and I have been wondering how you know when both tanks are fuel if the gauge is only showing one tank. The flow within the crossover hoses is much slower than the fill rate from the fuel fill and would therefore be inaccurate during fueling. I'm going to follow Rich's suggestion and wire a A-B switch in order to switch the gauge from one tank to the other.

You are correct on the filling being slow on the crossover tanks. My practice has been if I really want things full, find a quiet time at the gas dock. Fill up before they go to lunch....wait an hour while they are at lunch, fill again when they get back.

Personal opinion, I would not worry too much about adding a 2nd gauge, everything is going to equalize anyway after a few hours, what would the point be?

In my boat they also modified the crossover hose to be larger so that may help a little. However, I also have 4 tanks....two 110 gallon tanks on each side with two 50 gallon tanks also on each side... the 110's and the 50's are also valved to each other so that slows it down even more. I'm not sure why they did that, I know the tanks were replaced in 2014, may have been to make foe an easier tank replacement?

 

[Mainship Pilot]

Another option to get completely full, and as suggested above, to go to the fuel dock when not busy, and have them hose both sides of the boat at the same time, to take the crossover out of the scenerio. I personally have no reason to have 170 vs 175 gallons overall. Fuel dock is very convenient.

 

[LakeErieWX]

Thanks to everyone who responded to my question. I ran a wire from the port sending unit and wired an A-B rocker switch at the helm. I can now view the fuel level in both tanks (one at a time.) Now that the project is complete, I have an additional question as I adjust to life with a trawler. Fuel for the engine flows from the starboard tank and the excess returns to port. Before leaving the dock today, both tanks showed slightly more than 1/2 tank and the crossover valves were both open. While underway, the fuel level in the port tank raised noticeably as the returned fuel was flowing at a faster rate than the crossover. Is this normal? What happens if both tanks were relatively full -- is it possible for the tank to overflow?

Thanks,
Mark