Fuel tank site markings

[Sandy Feet]

The fuel tank on our Catalina 36 MK11 2002 is a plastic tank located under the cockpit port lazaret and is accessed from a wood panel in the aft stateroom. The problem I am having is that due to the tank being shaped to fit against the hull it is an irregular rectangle which is smallest at the bottom . Due to this, the fuel gauge is never correct. I have made a small door that i can open for a visual check of the tank since I can see the level of fuel when a flashlight is held against the tank.
My next step is to mark the side of the tank to show how much fuel I have in gallons. I don't want to have to drain the tank and then mark it as I refill the tank unless I have to.
Has any one done this already that could share the capacities at different levels .

 

[Stu Jackson]

deleted

 

[Stu Jackson]

I've found that exercise to be too much work.

You're absolutely right about the irregular tank shape and fuel gauges.

Recommendations?

Get in the habit of recording your fuel use and engine hours. Develop an hours per gallon record.

Many of us have done that for you already: M25 0.5 gph; M35 <1.0 gph.

23 gallon fuel tank? I figure 20 useable, fill up when half full, every twenty hours with my M25 at 0.5 gph.

No markings, no lookee...

I have a spreadsheet I've made for just this if you'd like a copy. Se the link in this post on fuel consumption.

http://forums.catalina.sailboatowners.com/showthread.php?p=1093658&highlight=fuel consumption

 

[VF84Sluggo]

Get in the habit of recording your fuel use and engine hours. Develop an hours per gallon record.

I've started a log doing exactly this with the Catalina 30 I recently purchased.

 

[Capt jgw]

There is a mathematical solution but you'd need access to the military super computers to figure it out. Once you know your gph, and know your tank capacity, you can make a pretty good guess as you use fuel after a fill up. I once had to calibrate a dip stick for a 300 gallon tank, adding 5 gallons at a time. Took all day. We had the tank empty for cleaning so at least that part was already done.