1989 300 Weekender Battery Wiring

K

Karen S Little

New Member
Jan 9, 2021
28
Boat Info
1989 SR 300 Sundancer
Engines
twin Mercruiser 5.7
Hi Our 300 has twin 5.7 and QS 4.0 with three batteries. does anyone have a wiring schematic on where each positive and negative of the batteries are connected. this boat has had someone change the wiring and I would like to try and get it back to the factory design

Thanks
 
Karen, I can send you a photo of my set up if it will help
 
it might thanks. im willing to run the cables the way I think it should but i sure would like a schematic

This is what is presently wired - its really strange :)

upload_2021-3-29_18-24-7.png
 
ALL negative cables should be connected together.
Without it the "both" position is useless
 
Thanks Bt.. do you think connecting each Battery Neg to a master Buss Bar would work? or is that not helpful (was thinking it might keep things uncluttered) Thanks
 
Your batteries should be next to each other , so just a short jumper from each neg post to each other. On my customers twins I add a cable between the engines. The theory is if a main eng neg cable should go bad, battery power will transfer over to the jumper to start an engine.
Buss bars add an extra connection point so you must also maintain those connections too. Battery cable direct to the engine. Noticed you only use 1 batt switch, I recommend individual switches. With your wiring diagram your alternators are bucking each other and most electronice hate that system. Second, you will never tell if an alt goes bad.
 
Bt Doctur said:
Your batteries should be next to each other , so just a short jumper from each neg post to each other. On my customers twins I add a cable between the engines. The theory is if a main eng neg cable should go bad, battery power will transfer over to the jumper to start an engine.
Buss bars add an extra connection point so you must also maintain those connections too. Battery cable direct to the engine. Noticed you only use 1 batt switch, I recommend individual switches. With your wiring diagram your alternators are bucking each other and most electronice hate that system. Second, you will never tell if an alt goes bad.
Click to expand...
thank you very good points
 
This is what I ended up with Comments welcomed.
 

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