Question For The Outboard Experts

[ttranger]

OK, I own an older boat with a 90 HP Yamaha 2-stroke motor. I have never run it very hard and it has performed flawlessly for many years. This year, for the first time, I have been stranded twice and unable to start the motor due to a "dead" cranking battery. The battery is an Interstate Series 27 Cranking Battery which i just purchased in March 2021. I recharged it after the last episode and the charger showed it as fully charged. I then had it checked by my local garage and he said it was fully charged and showing 97% capacity.

On my last trip the motor started fine in the morning but when I was ready to leave at 3 PM it wouldn't turn over. I had been running the outboard, electronics, etc. on and off throughout the day. My trolling motor runs off of separate batteries. Fortunately, I have a friend who was also fishing there that day so he came over and jump-started my motor from his battery. It started right up and I was able to get back to the ramp. I have a cutoff switch to all the accessories and I don't even leave my depthfinders hooked up when it's at home so I don't know where power could be draining from the battery. I figure the starter works fine as it fired right up with my friends battery. That leads me to believe that it might be a bad alternator but I am no mechanic so I would like to know what you guys think. Would one day on the water running the outboard, trim & tilt, accessories, etc. run it down to the point that it won't turn the motor over?

[EDR]

Yes. 27 series too small. You need more capacity. 29 minimum, but recommend 31.

[Ranger391v]

If you are only running a simple 5” or 7” depthfinder, maybe a livewell on timer, and cranking a 2 stroke Yamaha 90 …….. a good Group 27 should not have any problem. Now if you’re running a livewell constantly, cranking the motor a lot for short moves, and running big electronics with side/down imaging …. then Yes, that can kill a battery. We routinely run this motor (and others) on duck boats/ aluminum river boats, and typically do this with Group 24’s or 27’s without problems ……. but the electronics demand is minimal.

First I would take the battery to somewhere that can test it (auto parts store). I know you said it was basically new’ish, but I’ve been boat batteries fail for no good reason.

If battery checks out good, then start looking into motor not charging it enough. Also check electrical connections to make sure corrosion ain’t hurting you too.

With all that said, it’s always a good habit to ALWAYS charge your trolling motor AND cranking batteries as soon as you get home from fishing. This will help battery life as well as making sure that you have plenty of juice when you go next time.

Hope it helps!
-391v

[castforcash]

Make sure the alternator is working properly.

[A Wood]

My old ranger had a 115 johnson and I ended up having the rectifier, if my memory is correct, fry on me. Wouldn't put juice back in battery from alternator. Motor and everything ran fine till battery ran out of juice. Charge battery and would run fine again till battery was discharged. Found a burn hole through the gel when I finally figured it out. Pretty easy fix.

[jrh_67]

If you are only running a simple 5” or 7” depthfinder, maybe a livewell on timer, and cranking a 2 stroke Yamaha 90 …….. a good Group 27 should not have any problem. Now if you’re running a livewell constantly, cranking the motor a lot for short moves, and running big electronics with side/down imaging …. then Yes, that can kill a battery. We routinely run this motor (and others) on duck boats/ aluminum river boats, and typically do this with Group 24’s or 27’s without problems ……. but the electronics demand is minimal.

First I would take the battery to somewhere that can test it (auto parts store). I know you said it was basically new’ish, but I’ve been boat batteries fail for no good reason.



If battery checks out good, then start looking into motor not charging it enough. Also check electrical connections to make sure corrosion ain’t hurting you too.

With all that said, it’s always a good habit to ALWAYS charge your trolling motor AND cranking batteries as soon as you get home from fishing. This will help battery life as well as making sure that you have plenty of juice when you go next time.

Hope it helps!
-391v

^^^^This^^^^


I run a group 27 dual purpose battery in my boat with 2 helix 10's and a mercury 150 and my battery has never drained even using the livewell most of the day. I would take the battery out and get it tested and if it test good look into the charging system on your motor. I always plug in my charger to charge all batteries as soon as I back the boat in when I get home and all my batteries are over 4 years old and still going strong.

[Bill Reynolds]

Do you have a volt gage on the console? If so you should see 13.5 to 14.0 volts when the motor is running if the generator/rectifier is working properly.
Your depth finder may also have a voltage display.
I run a group 27 on my 115 Optimax and if I run the electronics and livewell all day, it will drop down to 10 or so volts even with making short runs. I would like to have a larger battery, but do not have room, not even a 1/4 inch.
I have a Perko switch with a setting that allows me to jump off one of the trolling motor batteries. I have had to use it a couple times even with the alternator working properly.
I always hook up my charger as soon as I get home.

[RFSims]

Actually the motor doesn't have an alternator, but a stator and voltage regulator. Having owned/ rebuilt and serviced a 1984 model that is still running today I am betting either the stator or voltage regulator is bad given a known good battery. A group 24 size marine starting battery is the only size battery used. A group 27 starting battery is more than enough.

[mactlman]

Yes. 27 series too small. You need more capacity. 29 minimum, but recommend 31.

27 plenty i have a 200hp with 2 graphs and livewells and never have issues? charging system bad or something wrong somewhere used a 24 for years and recently went to a 27 with talons but never run it down

[billnorman1]

It never hurts to have more amps available than you use. If you have over 13.5 volts when running the engine at a reasonable speed, your charging circuit is probably O.K. The true test of a battery is does it do what you need it to do. Apparently yours doesn't. It could be defective, it could be too small. I'm a big fan of the Duracell AGM size 31 at Sam's club for about $180.00. If you buy a new battery you should consider this one. I use them, never have any issues, but then again I have a Suzuki which will deliver 38 amps +.

[tj]

.

[bassdge]

Was the battery tested with a load? Battery water level checked?.
mid it has worked in the past and now having an issue, likely a bad battery is first check.
then look at charging system from motor.
charge the battery and check voltage. Turn on the electronics in the driveway and come back and check a few times over a period of time. I bet the battery will quickly go down .

[Mechanic Bob]

Do you have a Tach? If so and that has failed, you may need a new Stator and rectifier. I willing to bet you need a new Stator and rectifier.

[Bob]

As advised, clean all battery and electrical connections including grounds