Connecting my 20 HP manual start to my deep cycle battery. Advisable? Worth doing?

I have a manual start 20HP Honda outboard. I got it used and it didn't come with a cable to connect it to a battery. I don't currently use that 6 amp output for anything. I understand it only produces that 6 amps of output at full throttle. I also have a trolling motor connected to a deep cycle battery. Would it be worthwhile/advisable to get a cable to connect that battery to my outboard to help maintain the battery during a day of fishing? I use the two motors interchangeably so dont run the outboard all that much, depending on the day ( trolling/just casting etc. ). Thanks for any advice here!

Even if you only got 2 amp output to the battery while trolling with the Honda it would still be worthwhile in extending the available power to the electric motor. I have a similar setup and it has made a big difference. I used to have to put my deep cycle on a charger for a few hours when I got home from fishing but now it only takes about a 1/2 hour since I hooked up my new 20 horse motor last year. Especially useful if you were to plan an overnight trip with no 120 volt electricity available.

A small investment in wiring that is well worth it.

better than having a dead battery

Buy one of those $20 digital meters and you will be able to check your charging rates at various speeds.

Probably should know this, but how would you use the meter- i.e. on the battery posts- or touching the points to the output connector on the motor?

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Originally Posted by ahalls

Probably should know this, but how would you use the meter- i.e. on the battery posts- or touching the points to the output connector on the motor?

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You need to setup your meter to measure current. Place the leads in series with the red wire coming from the motor and connecting to the battery. Setup your meter to measure AMPS. Rev up the engine and you will see fluctuation in the output in your case up to 6 amps at max RPM as you previously mentioned.

Another way is simply to measure the voltage output in parallel from your motor which should be round 14 volts DC A fully charged battery is typically around 12.7 volts DC. This would indicate that the battery is receiving a charge but not of a known value.

Truthfully, any output is good and you should just go ahead and hook up the motor to the battery. You will be happy with the results.

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Originally Posted by ahalls

Probably should know this, but how would you use the meter- i.e. on the battery posts- or touching the points to the output connector on the motor?

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If you have access to a clamp on meter it's even easier. Just clamp over the positive cable with the meter set on amps and rev it up. It will tell you the amperage.

Thanks guys!

The majority of manual start outboards come with a low current lighting coil that will produce sufficient power to run lights, but it will also supply power to charge a battery. Not designed to provide enough current to recharge a battery after starting, and won't fully charge your trolling battery, but anything going in helps! I wouldn't try running the trolling motor at the same time as the outboard as it is possible to put too heavy a load on the lighting coil and possibly damage the coil, almost like butting a direct short across it should the batter be too low.