Pro's and Con's on an ON/OFF switch between the cranking battery and the outboard.

[AllyFishing]

Mercury 300XS manufactured July 2016
Serial number 1E053165
2013 Allison XB21 Bassport Pro (2 seater) .....not that it really matters

From new the outboard battery cables were run from the factory installed main ON/OFF (Blue Seas) switch that shut off everything on the boat. I was experimenting low voltage alarms on first start up of the day even with the Stealth 1 charging system plugged in over nite. I tested all positive and negative connections in the bilge between cranking battery and ON/OFF switch and detected a difference in voltage at the switch so after speaking to a few Mercury techs and those who have rigged Allisons advised to run the battery cables directly to the cranking battery and not thru the main shut down switch. Problem solved

As most bass guys we have 3 to 4 full size graphs, radio, MFD modules for either 3D or SS/DS etc., possibly a house battery (I do now), point 1, heading sensors etc. etc. which adds a drain and a slew of wires attached to a battery. I install a dedicated wiring harness for all my electronics with a dedicated Blue Seas fuse panel and manual ON/OFF breaker close to the battery.

I installed a heavy duty ON/OFF switch between my outboard and the cranking battery to shut off power to the outboard while I'm charging with AC power and for long periods of time off the water. So now my question(s) is this.... Do I really need to disconnect the outboard from power to charge on AC or for extended periods of time and does this shut down of power affect the outboard computer in any way??

Thanks
craig

And if need be I can explain the house battery/emergency start switch installation as well.

[Savage]

I don't use a Main Power Cut-Off Switch...….I have no charging issues.

[SilverFox579]

I don't use a Main Power Cut-Off Switch...….I have no charging issues.

Same here.

[AllyFishing]

Does anyone know what effect it has on the outboard computer though, if any?

[Stroker3.2XS]

No low voltage alarms, but a sluggish first startup of the day.

I installed a Blue Seas switch in 2013, like the idea of completely removing the power to the motor and the relays for the hydro plate and fuel pump. Replaced the 2012 Interstate group 27 with a Batteries +, X2power group 31 battery. Went out last weekend and again the first start was sluggish. But being the first time it has cranked over since December and cold air temperature.....? Next time I plan to connect the motor straight to the battery and see what happens. Maybe the switches get weak, internal corrosion or what not, and that's causing the voltage/ amp difference

[SilverFox579]

If you use a switch that doesn't match your engine's cranking requirement you can expect problems.

This switch will work and this one won't.

The first one has a cranking rating of 1200amps and the second only 700amps. If you want a switch between your start battery and engine make sure it meets engine minimum requirement.

[Savage]

Does anyone know what effect it has on the outboard computer though, if any?

No effect on the computer.

[EuropeanAM]

Does anyone know what effect it has on the outboard computer though, if any?

None, provided that there are no inadvertent reverse-polarity events.

It takes a pretty good battery switch to carry enough capacity for the engine and all it's many electrical devices... straight connections work best.

[AllyFishing]

Ok, so if I read that correct Don, there's no ill affects to the outboard computer cutting power with an appropriate ON/OFF switch OR leaving outboard directly connected to the battery even while hooked up to AC power to charge batteries?.

[AllyFishing]

No low voltage alarms, but a sluggish first startup of the day.

I installed a Blue Seas switch in 2013, like the idea of completely removing the power to the motor and the relays for the hydro plate and fuel pump. Replaced the 2012 Interstate group 27 with a Batteries +, X2power group 31 battery. Went out last weekend and again the first start was sluggish. But being the first time it has cranked over since December and cold air temperature.....? Next time I plan to connect the motor straight to the battery and see what happens. Maybe the switches get weak, internal corrosion or what not, and that's causing the voltage/ amp difference

Stroker, I had the exact same issue as I described above til I ran the outboard battery cables directly to the cranking battery.

[AllyFishing]

I have another question....since installing a separate house battery now for my electronics wired in with a Blue seas emergency start switch OFF/Battery 1/Battery 2/Battery 1+2 selections I now have an extra HD battery cable on the + and - post on my cranking battery. As many of us have experienced with so much electrical stuff wired up I was thinking of adding a separate set of posts mounted on an interior wall of the bilge to take some of the extra wires off the battery. Anyone do this or know any reasons not to?

[Savage]

How many batteries are in this boat now?

[EuropeanAM]

I have another question....since installing a separate house battery now for my electronics wired in with a Blue seas emergency start switch OFF/Battery 1/Battery 2/Battery 1+2 selections I now have an extra HD battery cable on the + and - post on my cranking battery. As many of us have experienced with so much electrical stuff wired up I was thinking of adding a separate set of posts mounted on an interior wall of the bilge to take some of the extra wires off the battery. Anyone do this or know any reasons not to?

Lots of boats do this- essentially a Ground Buss Bar and an ENCLOSED 12V+ Buss Bar.

Leave the ENGINE cables ON THE BATTERY for best results- run ample sized leads to the buss bar (based on what is running off that bar). Many we see have a 50a Circuit Breaker inline, 8 gauge* cable to the breaker/bars.

*Depending on your accessories/loads, you may need to adjust these figures.

[fishnfireman]

Lots of boats do this- essentially a Ground Buss Bar and an ENCLOSED 12V+ Buss Bar.

Leave the ENGINE cables ON THE BATTERY for best results- run ample sized leads to the buss bar (based on what is running off that bar). Many we see have a 50a Circuit Breaker inline, 8 gauge* cable to the breaker/bars.

*Depending on your accessories/loads, you may need to adjust these figures.

Good thread ….
Going to do this with my Allison.. never entered my mind that the cut off switch could be causing some of my issues .

[AllyFishing]

Yeah Mike I think the on/off switch in our boat is a bit weak to carry all the load especially the electronics of the 300XS. I didn't have a problem with my 250XS but the day after I got the 300 I experienced low voltage and starting problems. I tested voltage with my digital meter and there was a significant drop at the switch. After I ran the battery cables to the cranking I never had another problem.

Savage, I have 1 36V lithium up front for my Ultrex, a X2 Power 1150CC 78LB cranking battery in my rear port compartment and I just added a 12V Lithium 80ah in my bilge as a "house Battery".

Don, you have any suggestions on a heavy duty negative and positive bus bar? I don't need multiple fastening points, just one post for each

[EuropeanAM]

If you just want a HD post, you can get those in Blue Sea Systems (PowerPost Plus). There's got to be a bunch of them out there... and it would be REALLY easy to make your own. Just make sure that the POSITIVE post or bar is COVERED to prevent arching.

[AllyFishing]

Yeah that's what stumped me was finding one that is covered