I want to replace my trolling motor batteries. The current batteries are Interstate SRM 27. The local Interstate store is out of them. All I can find locally are various brands of a 27DC. Is the 27DC a suitable replacement?

Also, my Interstate batteries are over 5 years old. Should I assume they need to be replaced?

find deka and buy them, I run 3 grp 27 for a force tm and am real happy with them.

if they are 5 y.o. then all probably need to be replaced, load test them to be sure.

Duracell AGM's from SamClub are rebranded Deka's

I run the SRM-31 batts from Interstate. I get 6 - 7 years out of mine before replacement.

The way I look at it, If you're comfortable with a particular brand/type, it's worth the drive to go get what you want.
If your local store doesn't have what you want, see if they will order for you with no extra cost for shipping.

The Duracell 31 from Sam's is the best bang for the bucks.

You can buy the same battery from Batteries Plus with more warranty but it costs more as well.

Here we have a Battery Warehouse - A & D Batteries / Hydraulics that sells tons of batteries and they sell Deka batteries for a great price.

I went with the Dekas wet cell the last time. When they go, I think I will upgrade and go with Northstar's. But the Dekas are nice batteries. The Battery and Bulbs battery is a Deka. Just has their label on them.