Trolling motor battery space for 185 Competitor Sport

Well, after nearly 5 years of use with my green-top Interstate (Group 27) batteries up front, looks like it is time to replace. Without going out and measuring, would Group 31 batteries fit in the compartment under the rod locker? Looking to get a couple of LiFePO’s and the ones I’m looking at (12V 100Ah) are Group 31 size. Will also have to replace the ProSport onboard charger since it isn’t set up for lithium. Anyone looking for a used 2-bank onboard charger? Cheap…

I have a 24v 80ah that is also a group 31 size and it does fit great in one of the stock battery trays on a 175 competitor tiller.

I doubt 31 will fit. I have. Tournament sport and they wouldn’t. I have group 29 and it’s right.

Group 31’s will fit. I had 2 interstates in my 185 comp fsx. I switched to an amped outdoors 24v to free up one battery compartment so my reels could hang straight down.

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The Group 31 sized batteries fit very nicely. I put in 2 12V 100Ah LiFePOs and a NOCO onboard charger. The weight difference is quite striking and I expect substantially longer runtimes between charges.