I just bought a new mk terova trolling motor. I read in the instructions that you need to have a different battery for trolling motor so when you crank your engine it wont kill your trolling motor. I have a 14' lowe tin boat and I dont have extra room for another battery is there another way to put some kind of isolator or somthing else for this applictaion? My main motor is a 15hp evinrude 85 model with electric start.

You really need to have a separate battery for the TM.

Since you have a small outboard, is it equipped with a pull rope for manual start, and if so, are you able to start it that way? I ask this not to offend you, but if you do run your TM from your cranking battery, sooner or later you will find yourself with a battery too weak to crank your outboard. If you can manually start your outboard, you will be OK. If not, stick with separate batteries.

I agree. I would find some location on the boat to add a second batery. Otherwise you might find yourself up a creek without a paddle, if you know what i mean.

Yes I do have a pull start on my little evinrude. I was wondering if I could get away with using a smaller motorcycle battery to start the little evinrude? I have a harley that has way more compression and takes more juice to start I believe than the evinrude. I think I could put a smaller battery back there to do starting duties and use the bigger battery to do the trolling. I really like the convenience of easy starting although the little evinrude starts easy.

I do not see why you couldnt get by with a jet ski battery. much smaller, but I dont know, I would give it a try myself.

It'll troll for about 5 min with a jet ski battery. Maybe 10.
One other option, although I dont recommend it, is to use one HUGE dual purpose battery for both. I'm not a fan of them, though. They dont do either very well.

i agree with the guy who talked about the pull rope, also using ajet ski battery ....if your motor doesnt have a charging block you could look into having one installed