Familyfisherman Posted November 13, 2010 Report Share Posted November 13, 2010 I have a 17 ft Legend -- I bought it used. It has a Trolling Motor in front, with an on-board charger and 2 battery holders. It also has a cranking battery in the back, with downriggers, a fish finder and radio attached to it. The last couple times out the battery has drained down and failed to start part way into the day. It was fully charged before heading out both times. I have a couple questions: 1. Isn't there an alternator that should be keeping the cranking battery charged while driving? The motor is a 115 Merc 4-stroke. 2. The battery was drained accidentally this summer completely (kids left something on all night). However, it tested fine at CT...not that they're necessarily experts there... Do I need a new battery, or is it an alternator issue? Again, I'm not very mechanical but I would like to solve the problem if I can...hope to get out a couple more times this year before bass close up. Thanks -- the boat is stored outside in a shed, so it does get cold... Link to comment Share on other sites More sharing options...
Tom McCutcheon Posted November 13, 2010 Report Share Posted November 13, 2010 Have you been using the downriggers a lot the last couple of times out? Do a voltage test with the motor running at trolling speed and the radio, graph and downriggers operating. I know that at low RPM the riggers (if being used a lot ie: up and down)combined with the fishfinder and radio will draw a huge percentage off the battery. It could be like you said an alternator problem, check the belt for tension. Tom. Link to comment Share on other sites More sharing options...
Fang Posted November 13, 2010 Report Share Posted November 13, 2010 Are you trolling with the 115? If so you should be putting enough juice back in the battery. Downrigging all day while running a color sonar will drain down the battery. Suggest putting a 12v gauge on your dash to keep an eye on this. I do the same in my boat and have the biggest amp cranking battery I can buy Link to comment Share on other sites More sharing options...
scugpg Posted November 13, 2010 Report Share Posted November 13, 2010 (edited) Your sonar may have an option to display voltage as well. Edited November 13, 2010 by scugog Link to comment Share on other sites More sharing options...
NBR Posted November 13, 2010 Report Share Posted November 13, 2010 If you are not charging the cranking battery every time or two times you go out you might be pulling the cranking battery down. Outboard built in chargers don't put out a lot of charge. I learned this the hard way which is why a part of my boat equipment is a set of jumper cables. I have a 17 ft Legend -- I bought it used. It has a Trolling Motor in front, with an on-board charger and 2 battery holders. It also has a cranking battery in the back, with downriggers, a fish finder and radio attached to it. The last couple times out the battery has drained down and failed to start part way into the day. It was fully charged before heading out both times. I have a couple questions: 1. Isn't there an alternator that should be keeping the cranking battery charged while driving? The motor is a 115 Merc 4-stroke. 2. The battery was drained accidentally this summer completely (kids left something on all night). However, it tested fine at CT...not that they're necessarily experts there... Do I need a new battery, or is it an alternator issue? Again, I'm not very mechanical but I would like to solve the problem if I can...hope to get out a couple more times this year before bass close up. Thanks -- the boat is stored outside in a shed, so it does get cold... Link to comment Share on other sites More sharing options...
Familyfisherman Posted November 13, 2010 Author Report Share Posted November 13, 2010 Good thoughts. No I haven't used the downriggers at all. I have used the colour finder...mostly drifting for bass, so I only use the motor to move back to the start of the drift. There is a gauge on the dash to check amps. I've never even taken the lid off the motor, so checking the belt tightness is a bit beyond me When I say not mechanical...I basically mean mechanical idiot Link to comment Share on other sites More sharing options...
Terry Posted November 13, 2010 Report Share Posted November 13, 2010 I think you need a new battery or the alternator is not working right with mine the battery can be dead, I get a boost and 5 minute drive and the battery is charged enough to start the motor you say you have 2 batteries I will assume your trolling motor is 12 volts charge up the starting battery then hook it up to your trolling motor, then let the motor run at full speed and see how long it runs, should be hours if it lasts a long time it's not the battery... it's the alternator that is if it's not a short somewhere when the key is on..but one check at a time..see what happens Link to comment Share on other sites More sharing options...
Tybo Posted November 13, 2010 Report Share Posted November 13, 2010 What is the gauge reading right now. Link to comment Share on other sites More sharing options...
Rob Posted November 13, 2010 Report Share Posted November 13, 2010 whatever you do, don't leave out in the cold. You will freeze it and then it is screwed. Also you need to top the battery up with a full charge each time you use it. Batteries will discharge constantly so keeping it topped up will lengthen the life of it. Deep cycle batteries have various cranking amps so make sure you have one that is adequate for you motor. Rob C Link to comment Share on other sites More sharing options...
vinnimon Posted November 13, 2010 Report Share Posted November 13, 2010 I have a 17 ft Legend -- I bought it used. It has a Trolling Motor in front, with an on-board charger and 2 battery holders. It also has a cranking battery in the back, with downriggers, a fish finder and radio attached to it. The last couple times out the battery has drained down and failed to start part way into the day. It was fully charged before heading out both times. I have a couple questions: 1. Isn't there an alternator that should be keeping the cranking battery charged while driving? The motor is a 115 Merc 4-stroke. 2. The battery was drained accidentally this summer completely (kids left something on all night). However, it tested fine at CT...not that they're necessarily experts there... Do I need a new battery, or is it an alternator issue? Again, I'm not very mechanical but I would like to solve the problem if I can...hope to get out a couple more times this year before bass close up. Thanks -- the boat is stored outside in a shed, so it does get cold... Do yourself a little favor! Grab a multimeter and set it on dc voltage! Put the black wire one the neg post of the battery and the red in between the posts where the sticker is ! What is the reading? 1 volt 2 or 12.6? Moisture over top of the battery can play havic over a weeks time! Link to comment Share on other sites More sharing options...
irishfield Posted November 13, 2010 Report Share Posted November 13, 2010 Maybe everyone is missing something here... are you indeed saying that you start the engine.. drive up the drift.. shut the engine off and then drift along with fish finder etc on and then start the engine again.. over and over.. or are you leaving the engine running during the drift? Link to comment Share on other sites More sharing options...
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