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24 v batteries vrs 12 v system contemplating adding a 12 v transformer

Hey all, new to boating and boat ownership and expense, oh boy


Sharing with friend and fixing up an old very worn 1979 Chrysler 14' Striper w/ 1988 US Marine 35 force outboard.
Live land locked in Colo Spgs CO so it'll just be used on lakes and such.


Friend thought it's a 24 volt system and got a deal on 2 24 volt deep cycle batteries (got 2 since it was a good deal and he would like to/thinks it's a good idea to add a trolling motor in the future).
2 batteries is a tight fit in the battery compartment to fit between 2(6? gal. gas tanks with tank selection switch).


However I discovered the boat/motor system is a 12 v system but that if we add a trolling motor, 24 volt trolling motors are far better and not much more $ than a 12 v.


So.... it's my limited understanding and guessing that maybe the ideal set up is 1 12 v battery for now and then a second 12 v battery when a 24 v trolling motor is added in the future where the two batteries could be wired both in parallel and series to provide both 12 v for everything and 24 v for a 24 v trolling motor.


Q 1. Is this correct?




But.... my neighbor does not think he can take back the 24 v batteries and is wondering if we can install a 12 v transformer 30a we have seen some on e-bay for like less than $30 to power everything off the 24 v batteries although I don't think 30a is enough to feed the 35 force outboard starter motor and that a transformer might drain the batteries all the time and is getting into unwanted complicatedness....


Q 2. Any input on this?




Thank-you for any advices!
 
But.... my neighbor does not think he can take back the 24 v batteries and is wondering if we can install a 12 v transformer 30a we have seen some on e-bay for like less than $30 to power everything off the 24 v batteries although I don't think 30a is enough to feed the 35 force outboard starter motor and that a transformer might drain the batteries all the time and is getting into unwanted complicatedness....

Ayuh,.... it sounds like "unwanted complicatedness", to me....
 
Generally, I think it is a bad idea to completely step down 24 V batteries to 12 V. That stepper will not normally work in both directions. That is, you will not be able to charge the 24 V batteries off the Force 35. Now, I haven't looked at this stuff for a long time, so there may be a standard solution out there somewhere that I am not aware of.

If I were doing this, I would install a 12 V for starting and instrumentation and hold the 24 V batteries for the trolling motor. Besides. That lets you place the 24 V batteries far forward, which will provide better ballance to the boat. You will need a 24 V charger for those batteries.
 
agree....keep it simple...on a boat that size 12v trolling motor will do the job....one 12 volt for ignition and one for trolling motor....go with 24volt motor now with the batteries and you are locked in...sooner or later batteries need replacing...
 
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