Now that I'v learned all about the Mercathode, I have another thing that has been bugging me that maybe someone can help me with. With the boat at rest, the fuel level gauge reads fine. Under way the needle freaks out and starts jumping all over the range. You think gauge, sender, loose wire or?
Thanks for any help.

Cheap float sender !!!!!

Use an electric sender ,they dont have a float !!!

The only true solution to erratic or inaccuracte gauges is:

http://www.livorsi.com/catalog/senders.htm#fuel_level

We need to know the depth of your tank to quote you properly.

Let us know if we can help.

Elite Marine

float sender.

When you say underway, is that at idle?

Assuming you me underway as on plane then... Typically, the standard issue sender provides poor damping to begin with. If you know that at one time your fuel gauge did not do this, then you may want to try replacing the sending unit.

Personally, I would just live with it, since it's probably not real accurate anyway, espcially if you have a irregular shape tank.

Another thing is to make sure you are getting good signal to/from your gauge and to/from your sender. I had a problem this year with a finicky gauge after I replaced some battery cables and finally found out during winterization the sender wire was rubbing on the water pulley

It was funny too because I was ****ting on my last run hoping I would run as much gas out of the thing without running out of gas!

Check the ground wire connections at the sender.

I have the same thing and replaced the gauge and still happens whats left is wire and sender

Thanks to everyone for the help. Sounds like I need to check wires and then the sender, and most likely spend more money. It's a boat, but as I like to say "Fun is Cheap at any Price" and boats are a lot of fun.