One battery for trolling motor and starting?

Salmonseeker

Petty Officer 1st Class
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Jun 11, 2005
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298
Hi everyone,<br /><br />I just purchased a 12 volt 55lb thrust trolling motor. It is a Motorguide. <br /><br />When I was reading the installation instructions regarding using one battery for your main engine and trolling motor. They recommend not to do this due to electrolysis issues. They write "Using the engine starting battery as a source of power for any trolling motor may cause electrolysis on metallic parts". <br /><br />Now when I go to the Motorguide website they have a wiring diagram showing a trolling motor hooked up to the main engine battery. Here is a link motorguide.com/index.pl/12_volt_and_24_volt <br /><br />The battery I will be using is a larger deep cycle. The deep cycle battery has more marine cranking amps than the starting battery the boat came with. I used it all last year with no problems. It says it is a deep cycle battery and not a dual purpose.<br /><br />Now that I want to install a trolling motor, I want to know if it is okay to use one battery for my trolling motor, accersories, and the main engine? What will be the issues with electrolysis? Can they be avoided?<br /><br />The motor is a 2004 Johnson 50HP 2 stroke and can be started manually if the battery ever did run dead. I know beacause I had this happen with the original battery. So I am not to worried about this happening.<br /><br />I plan on using a 50 amp circuit breaker with a on/off switch to the trolling motor. This will allow me to turn off all power to the trolling motor when not in use.<br /><br />Any thoughts? This is my first trolling motor and need some help.<br /><br />p.s. The trolling motor probally will not see alot of use, but that could change if it helps me fishing. I really don't want to install a second battery if I can avoid it.<br /><br />Thanks Jay
 

JB

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Mar 25, 2001
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45,907
Re: One battery for trolling motor and starting?

I have always used only one battery, a BIG dual purpose. Never had any problem.<br /><br />BTW, I never used a troller in salt. Might make a difference.
 

Salmonseeker

Petty Officer 1st Class
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Jun 11, 2005
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298
Re: One battery for trolling motor and starting?

Thanks, thats what I was thinking.
 

waterone1@aol.com

Lieutenant Junior Grade
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Oct 10, 2004
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1,235
Re: One battery for trolling motor and starting?

From an electrolisis issue...that is a real crapshoot. Depends on what metals are "hanging in the water". I think they are just covering their arses. Look at both motors and drives yourself from time to time.....do you see any corrosion or pitting ??
 

Salmonseeker

Petty Officer 1st Class
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Jun 11, 2005
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298
Re: One battery for trolling motor and starting?

I will keep an eye on it. I just bought the motor and have yet to insatll it. I just wanted to be sure it can be done without any problem.<br /><br />You are probally right about them just covering their arses.<br /><br />Thanks Jay
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,544
Re: One battery for trolling motor and starting?

Just registered what you were talking about with electrolysis. I THINK that if you keep the cases at the same potential, you won't have a problem. If you do (have a problem with corrosion; get some sacrificial Zinc anodes (like Merc has on the skeg) and a stainless steel (like a radiator hose) clamp and attach one to the shaft of the trolling motor.<br /><br />Otherwise, if you have a big battery and don't do a lot of trolling and have a low-med hp motor it ought to work.<br /><br />My unofficial 2c, but makes sense to me. Grin<br /><br />But I have been in a boat in '71 where I only had one batt and had to rope start an 85 hp Chrysler cause I ran the battery down running the t motor in a high wind situation. Did it (rope started) but needed a lot of carbohydrates to get the muscles up to it. Grin<br /><br />Mark
 

JB

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45,907
Re: One battery for trolling motor and starting?

It is a big help to use a troller with the battery condition guage on it. It will warn you if the battery is getting into a danger zone for starting.
 

Salmonseeker

Petty Officer 1st Class
Joined
Jun 11, 2005
Messages
298
Re: One battery for trolling motor and starting?

The motor does have a battery guage on it. I will have to keep an eye on it. If the battery ever did die,I am not that worried. I have started it once with the emergency rope start and it worked alright.<br /><br />I am gonna go ahead and try the one battery. If I have any problems I will rethink the situation.<br /><br />Thanks for the advice, Jay
 

MajBach

Chief Petty Officer
Joined
Jun 21, 2003
Messages
564
Re: One battery for trolling motor and starting?

I actually have the same trolling motor. ALthough I currently use two batteries - one deep, one dual - I used to only use a deep cycle for starting and trolling and I never gave a moments thought to 'caring' for the battery (but I did make sure a had a rope for manual starting). I have both batteries hooked up to the O/B for charging via an isolation switch. I've read all the recommendations etc. about dual purpose, marine...you name it. I have concluded that it's far more enjoyable not to worry about it and have to buy a new battery PERHAPS one year earlier than I might have if I babied it.<br />Up until my last battery, all batteries I purchased were staight deep cycle - not marine, not dual. In my old boat, I used to suck it dry with the trolloing motor every trip and charge it on a 10 amp when i got home. After about 3-4 years when it didn't quite last me the weekend anymore, it would go from the boat into one of my vehicles (incidentally, after doing this the first time, I will NEVER buy a straight car battery again). These 'used' deep cycles typically lasted longer in my cars than did a store bought auto battery: 6-8 years. Matter of fact, last year I tossed the original deep cycle I got from my first trolloing motor back in '93.<br />I now have a new boat with an O/B with a 16 amp alternator. I've owned it for 6 years. The starting battery was the first to go (last year) so I put my deep cycle in it's place and purchased a new dual purpose - simply because the guy I bought it from was selling it cheaper than his typical straight deep cycles.
 
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