Mercury 15 HP 4 stroke - How much electronics can be powered at idle

[JGeiger]

I am getting ready to take a Canadian fishing trip and I am concerned that the lodge's Mercury 15 HP 4 stroke tiller motor might not have enough juice available to power my fish finder equipment that I want to take with me.

My electronics is supposed to draw an average of 47 watts (4 amps @ 12vdc). The boats are equipped with a very small battery for starting the motor. Most of the time we will be trolling using the MERC motor at idle.

Am I going to need to take a secondary battery with me to power my electronics?

If I need to take a second battery, is there any way to connect it to the boat's circuit to charge it when operating the motor above idle?

Thanks in advance.

[wmitch2]

I am getting ready to take a Canadian fishing trip and I am concerned that the lodge's Mercury 15 HP 4 stroke tiller motor might not have enough juice available to power my fish finder equipment that I want to take with me.

My electronics is supposed to draw an average of 47 watts (4 amps @ 12vdc). The boats are equipped with a very small battery for starting the motor. Most of the time we will be trolling using the MERC motor at idle.

Am I going to need to take a secondary battery with me to power my electronics?

If I need to take a second battery, is there any way to connect it to the boat's circuit to charge it when operating the motor above idle?

Thanks in advance.

You should check to see if that motor even has an alternator or if the battery is just for starting it. I would think you'd have to have a seperate battery for any electronics.

[CatFan]

That outboard produces about 10A Max. Put up an overlay on the screen to monitor battery voltage. If it stays above 13V, you are likely good to go, as that means more is going into the battery than is coming out.

You can always pull start it.

[Ben Danbleume]

Isn't 4 amps a large draw? Carbon 12 only draws 2.3 according to spec sheet.

[piketroller]

If it’s a newer motor it should also have a pull start rope. If battery capacity is an issue, just use that to start the outboard and run to a new spot every four or five hours for some recharge and you should be fine.

[JGeiger]

Thanks for everyone's input.

Yes, 4 amps seems large to me as well. It is a Garmin 106SV and the LiveScope LS32. I chatted online with Garmin and the staff member was suggesting that it will be even higher than 4 amps under certain conditions.

I am in the process of making a separate lithium battery box. I am going to equip it with a battery selector switch arrangement that will allow me to connect to the boat's battery and then switch over to the lithium for backup purposes.