2000 406 diesel auxiliary fuel tank info

[Summer Place]

Hello, Hoping to get some info on aux fuel tank set up for a 406. From what I can tell, the port and starboard tanks each hold 97 gallons and the aux tank at the back holds 142 gallons. When I look at the fuel valves at the stern in the engine room there are 2 -3 way valves I believe they are labeled Port aux off and Starboard aux off. Both are currently pointed to the thier respective side. I assume if I wanted to draw from the Aux tank I would have to manually move the valve to the aux position for each one. I'm hesitant to try because I don't know how long the fuel has been there but we are getting ready to take and extended trip and I may need to draw from it. I'll plan on adding fresh fuel and carry a bunch of spare filters.

Any input would be appreciated!

Thanks!

[Viper]

Welcome aboard.

Do you know how much fuel is in there and how old it might be? Really does boil down to that. When in doubt, take a sample and have it tested or pump it all out and start fresh. The condition of the fuel itself is only half the concern, if there's a lot of water in there from condensation, you don't want any passing through your filters and on to your fuel system. In any case, it's beneficial to have spare filters on board and keep an eye on the Racors (if applicable) to check the condition of the fuel and signs of water.

[buster53]

Ok, I have a Carver 356 basically set up the same way. 95 gal saddle tanks and 125 gal Aux tank built into the swim platform. As a Carver owner who experienced bad fuel issues a few years ago, here’s my advice.
Since you have no idea how old the fuel is, get a fuel polishing/removal guy to check the fuel in your tank. You will immediately know if you have water in the tank and it can be quickly removed. Even without testing the fuel, a good fuel guy can get a good feel of how good the fuel is just from appearance and smell. Nasty looking fuel obviously needs to be removed. Of course, testing may be the best course of action.
Now that you have determined how good or bad your fuel is and you have taken corrective action to remove bad fuel here’s my advice going forward. Always use all three tanks to insure you have good, fresh fuel in all tanks. Best way, say you are taking a 50 mile trip. Use the aux tank to get there and saddle tanks to get home. 2 things happen when you do this. You are turning your fuel over in all 3 tanks and by using the aux tank first, you are lightening your weight load in the ass end of the boat first which gives you a little better weight balance.

[Summer Place]

Thanks for the help! no idea how old the fuel is, I've had the boat for 3 years so its at least that old. It looks to be about 1/4 full. Now off to find someone who can polish or pump out the fuel. I'll plan on pulling a sample to get a look.
I do have dual racors and the primary filter on the motors.

[g36]

Hello . I have a 405. You will have 2 rear tanks instead of 1 large in 405/406 where the the 355/356 have 1 large rear tank. The rears are apx 75 ,gallon each and the side tanks will be apx 95 or so each with boat total fuel capacity of 342.