Another wiring question

Hi everyone, I have a wiring question and I have read all the stickies and done a considerable amount of research but I cant find a definitive answer to my problem and Im no electrician (at all) Here's the situation, I recently acquired a 1988 Wahoo with a 85hp Force outboard. The boat has a 2 battery setup, 1 for the motor and 1 for the accessories. The boat also came with a Perko (1, 2, both, off) and a Newmar 1-2-70 isolator. The wiring was a mess and most of the accessories and other wiring was disconnected when I got it. I have since removed all of the old broken accessories (fish finder, CB) and Im ready to put in my new fish finder and trolling motor. I have 3 questions on this before I re-wire this

1. I have seen/heard 2 different ways to wire the batteries, motor, isolator and switch. One has the batteries connected to the switch and the switch connected to the isolator (http://order.waytekwire.com/INC/Marine Bat Iso 180119A.pdf). The other had the batteries connected to the switch and the isolator directly connected to the batteries as well (as it was when I got the boat). What is the correct way to hook this all back together?

2. I also want to add a third battery as the trolling motor Im getting is 24v so I'll need 2 batteries to run this. Does that affect the wiring on question #1 (aside from connecting the 2 deep cycle batteries in series)?

3. Since Im not electrician the isolator seems to complicate things quite a bit, is it really needed?

Any help would be VERY appreciated!

Re: Another wiring question

Adding the 24 volt trolling motor simplifies the system greatly since that would mean you could throw away the switch and isolator. If you really plan on a 24 volt troller you need two of those batteries in series for 24 volts. You cannot charge both of them plus the starting battery from the engine. In fact the engine will have a tough time charging two of them. So leave the two troller batteries totally as a separate system. Add an on-board dual bank charger and plug in at the dock. The engine will take care of the starting battery. Even if it were possible to charge both troller batteries from the engine, you would need to run the engine wide open for miost of the day to top them off. It simply is not a reasonable plan to incorporate a switch and isolator.