Boat is new to me this season but put on many hours already this year.

So, I've been dealing with some intermiten starting issues for the last couple weeks. Seemed like not enough juice to start the boat so I bought a new battery. I replaced the battery with the same battery that was in the boat. An Interstate SRM-27B. Didn't fix the problem. Now, I've put a new starter in, and still hasn't fixed the problem. It seems like my voltage is good and plenty of power for all my lights, dash, stereo but still not enough juice to crank it over consistantly.

What next? I am wondering if I have the wrong battery for my application. My merc manual says it's enough CCA(650) to start the motor but I'm wondering if the deep cycle is not the right battery?

650 cca should be enough, always use a deep cycle battery, volt meter should be about 13.5 on gauge when running, maybe you need new cables from the battery to starter.

I had the same problem starting my 29ft fountain! I traced the problem to the positive wire going from the on/off switch to the starter. The bad connection was at the starter. It left me at the docks pissed for about 45 mins until I found the problem. Thank god I carry a nice tool kit onboard! The wire was corroded in the terminal. I couldn't see it since it was under the shrink tubing. With boats there is a lot of moisture and corrosion are very common. Good luck!

I finally found the problem. Similar to paulsgts except it was one of the posts on the back of my battery switch. Litterally corroded right off the back of the switch. So that's an easy fix except for getting the corroded en off and re/crimping a new end on. That's gunna be a PITA.