Starting and deep cycle battery all in one combo or separate batteries.

[Mike bob]

I have a 14 foot aluminum boat with a 1976 25hp Evinrude electric start. I use a 36 lb thrust transom trolling motor. The fuel tank is a 6 gallon OMC. The problem I am having is too much weight in the back of the boat with 2 batteries and fuel tank. I do a lot of trolling shorelines for musky. Are the all in one combo starting/deep cycle batteries any good? Which brand? Where can I get one. OR Should I continue with 2 batteries. Need your opinions.

 

[glenn property of pam]

I presume that you are using one battery for the starter motor and one for the trolling motor. If that's correct then I would try to rope start the motor when its warm (battery wont be flat the first time you use it on a day out but maybe low later after a lot of trolling). If I could rope start the motor with out to much of a fight then I would be willing to run on one battery.

 

[wrench 3]

The combination batteries are good but as Glenn points out, you don't wined up with a spare. Could you make up a longer fuel line and move the fuel tank forward?

 

[Expidia]

You could get away with it. It depends on how much trolling you do. Not good to run even a deep cycle to flat so pick up a cheap battery tester to see how low you are running it down and stop around 20% power left. make sure you re-charge it the same night. Its all about the amps. I noticed walmart everstart batteries dont list amps on their cranking batteries. They list amps on their deep cycle marine batteries. If you find your combo battery does not last long while trolling thats because you want a deep cycle of at least 100 amps. I have a combo everstart that i bought because I run it down with the stereo while lounging around in a bay for a few hours. This ruins a regular starter battery. I also just picked up two more everstart deep cycles that are 109 amps each for like $79 each group 27 is the minimum for trolling use, better than a $74 group 24 Weighs only a few more lbs and the case is only like an inch wider. When i had a 14 foot basic aluminum I went to home depot and bought like 12 feet of black 8 gauge wire and same in red. Then I bought a $5 plastic battery box with a cover at walmart and kept my trolling motor up front rather than the gas tank. Try the combo and first see how long it last trolling. If not that long, pick up a group 27 deep cycle. Cranking even a 25 hp gets old fast especially after its cold again after trolling for a few hours. I had a 2006 merc 9.9 4 stroke and I hated pulling the rope since it was not electric start!

 

[Pony]

To me....the answer depends on if the motor can be pull started or I should say pull started without taking the cover off and getting a knotted rope.

Can't pull start - I would get a longer gas line and put that in the middle. Get a Group 24 battery for the motor. Get a Group 27 or better Deep Cycle and put that up front by either doing what Expedia did, or just get a trolling motor extension kit. They are like $30 and are 20ft of both pos/neg cable with terminals. If the motor can't be pull started, I wouldnt want to only use one battery and get stuck not being able to start the main motor.

Can pull start- I would get i big Deep Cycle and again move it to the front as before. It will easily start the boat if you want to use it when not trolling.

 

[Mel Taylor]

A friend of mine solved that problem by using one starting/deep cycle battery and carrying a motorcycle battery along as a spare starting battery just in case he ran the marine battery down.

I know someone else who doesn't use a trolling motor or anything else electronic who uses only a motorcycle battery as a starting battery. Both have 25 horse Evinrudes on 14 foot tinnies. Do be aware though that both of their motors are late
1990s models with electronic ignitions. I don't know whether that would make a difference or not.

 

[Wee Hooker]

Not sure why a combo battery would do any better than a straight deep cycle? Your 25 hp draws so little CCA that the deep cycle should handle it fine. In fact if you hit to power on a straight 12V 36# electric, it probably draws more amperage from the battery than a starting cycle on your 25 would. Couple of soultions I can see. Run your second DC battery out of the bow and run the power back to either the TM or OB. This assures you always have a good starting battery since it remains isolated.
Second option to save weight may be to run one group 27/29 battery. It will give you more reserve than a group 24 and will save 30# or so over the pair of 24's. It won't prevent you from over draining the battery with the tm though.
Lastly, you can upgrade your TM to one with a chopper circuit like the varimax or maxumm. Both will save significant juice and may allow you to get away with one battery. ( Hard to say here as how long and fast you troll will have a big effect.)

FWIW, I have started my outboards in the 15-30 hp range near exclusively on DC batteries without issue for the last 20 years.
I also now run a 55# Varimax TM on a single DC battery that also starts my 30 hp Nissan 4 stroke. I have not killed the battery to the point it will not start teh OB but then again, i keep a second battery a flip of a switch away stowed up in the bow.

 

[Pony]

Not sure why a combo battery would do any better than a straight deep cycle? Your 25 hp draws so little CCA that the deep cycle should handle it fine. In fact if you hit to power on a straight 12V 36# electric, it probably draws more amperage from the battery than a starting cycle on your 25 would. Couple of soultions I can see. Run your second DC battery out of the bow and run the power back to either the TM or OB. This assures you always have a good starting battery since it remains isolated.
Second option to save weight may be to run one group 27/29 battery. It will give you more reserve than a group 24 and will save 30# or so over the pair of 24's. It won't prevent you from over draining the battery with the tm though.
Lastly, you can upgrade your TM to one with a chopper circuit like the varimax or maxumm. Both will save significant juice and may allow you to get away with one battery. ( Hard to say here as how long and fast you troll will have a big effect.)

FWIW, I have started my outboards in the 15-30 hp range near exclusively on DC batteries without issue for the last 20 years.
I also now run a 55# Varimax TM on a single DC battery that also starts my 30 hp Nissan 4 stroke. I have not killed the battery to the point it will not start teh OB but then again, i keep a second battery a flip of a switch away stowed up in the bow.

When I first read the post I was thinking that if he was trolling for musky he is moving at a pretty fast clip, but didn't consider he may be casting and not dragging lures.....if dragging lures, he is going to drain the TM fast at that speed....which is why I would want to have a second deep cycle for starting the main motor if the thing cannot be pull started. A DC would be more than enough to start that motor as you said.

 

[Wee Hooker]

I would agree Pony. While there are some ways to compromise, they all involve risk of having an OB that won't start at the end of the day. Having had dozens of small tin boats over the years, I'll safely venture that moving a battery and/or fuel tank forward is the best solution and will help boat control and stability without giving up anything for reserve power FWIW, a Cheap set of jumper cables from walmart can be adapted quickly for ths purpose as can an extra 10' of automotive fuel line.