installed a 9.9 electric start, question?

[3chap0]

Mechanic told me, before I hook the wires up to one of my 12 volt batteries, to check into a battery isolator. I have a 24 volt trolling motor hooked to the batteries. He said if I had some kind of surge of power, it could burn up wiring in my 9.9 merc 4 stroke, if I hooked up one of the 12 volt batteries . Or he said to get another battery for the starter, which I didnt really want 3 batteries in my 16' boat unless I could find a real small one, just to crank the 9.9 over with. I dont think battery isolaters are that cheap either...any suggestions...Wondering how small of a battery I can get away with, for cranking over my 9.9? I have got some little duck decoy batteries for my mojo decoy, I will have to see what kind of amps they have.....

 

[Georgesalmon]

Re: installed a 9.9 electric start, question?

If the batteries your talking about are only connected to the trolling motor I think you'll be fine. Just hook to either one> Where could a surge come from? Trolling motor will draw current, not add any. 9.9 will actually charge the battery it is connected to. Not much but a little bit It won't even see the other battery, electrically speaking.

 

[JB]

Re: installed a 9.9 electric start, question?

I agree with George. You don't get surges in a marine DC system. Run the starter and other 12V devices on battery #1, Use battery #2 to boost that to 24V for the troller.

 

[3chap0]

Re: installed a 9.9 electric start, question?

I agree with George. You don't get surges in a marine DC system. Run the starter and other 12V devices on battery #1, Use battery #2 to boost that to 24V for the troller.

Ok, all I got is the running lights, depth finder, spot light, and the starter on one. I guess I will put my positive from trolling motor on other battery, and ofcourse negative to this one. Then my jumper will hook up to the negative across my trolling motor positive battery. and vise versa on the other battery. Sorry to be so rookie..........I dont know what the mechanic was talking about, on the backwards feed......

 

[Georgesalmon]

Re: installed a 9.9 electric start, question?

Don't feel rookie, I spent a lot of time thinking and drawing schematics before I thought I had it figured out. Leave everything wired as it is and just pick one battery and connect the 9.9 both pos and neg to that one. On my boat I put my kicker motor on the battery that has all the house wiring attached because I troll a lot more hours than I run the "big" motor and my 9.9 merc pro kicker seems to just keep up with nav lights, depth/GPS, VHF, and downriggers just fine.

 

[Silvertip]

Re: installed a 9.9 electric start, question?

STOP! You need to think about WHICH battery you connect not only the motor to, but your accessories as well. here is how it should be done. I've explained the accidental ground situation in a 24 volt system a dozen times before so you can use the search feature to find those threads and the explanation. You should connect 12 volt accessories that are powered from a 24 volt system to the battery that has the SYSTEM ground on it. That provides every device including your motor with a common 12 volt ground point.



And here is a diagram illustrating the less safe way to do this. Study it carefully so you learn the dangers of doing what you are doing.
Just so you know, I want you to "learn" not just "DO". CHASSIS ground is the issue here. Not just the NEGATIVE lead on the device. Another hint: Is your boat metal?