I have a 2man pelican boat. Im putting a small lowrance  on it .  I have a small battery an case i could use to power the lowrance. My question is,how long would this battery last? The fish finders a smaller one also. Thanks for any help.

A little Google search and I found that the battery is rated to 9 amp-hours. Check the manual on the unit - or do a Google search on the model - to find the 'Current Drain' for the unit.

 

Searching on the Hook-4 I found that it draws 1.1 amps - so that battery would last a little over 8 hours (9/1.1=8.18) using a Hook-4 or Hook-5.

 

That's assuming the battery is in very good shape and hasn't been subjected to too many drain-recharge cycles...the more cycles it's been put through, the less it'll hold.

Just like @MN Fishermentioned exactly, depends on how big the screen and how much amp use per hour. I have 4” screen lowrance which draw around 1amp and my 4.5 amp battery last around 5 hours. Bigger screen normally draw more power.

Thank you very much guys