251 ce battery/electrical issue

[billbass]

probably shouldn't switch batteries with motor running....

There should be no problem making a battery switch change as long as you don’t go through the off position to do it. That is, if the switch is set to battery number one and you want to go to battery number two then you rotate through switch position “1/2”. That is the “make before break” option. When you go through the 1/2 position your motor and other electronics never sees 0 V. Everything on the boat is always connected to a 12 V source when you rotate the switch through the 1/2 position. If you rotate through the off position then everything n the boat definitely sees 0 V at the moment the switch is in the off position. Don’t do that. Supposedly that could damage the engine

 

[billbass]

Do not put dielectric grease on the battery posts or cable connections. Dielectric grease is an isolator, in that it does conduct electrical current. After your connections are made with clean dry components, then coat them with a corrosion inhibitor.

The more proper term is that dielectric grease is an “insulator”, but in a sense you could say it’s an “isolator”. An insulator insulates any voltage carrying conductor from something else. The plastic jacketing on every conductor is an insulator. All the plastic parts everywhere having to do with electrical items are made of an insulating material.
I hate to challenge you, but I don’t want someone to go completely off-base. I think he just accidentally left out the word “not”. I assume that you meant to say above that dielectric grease does NOT conduct electricity. That would be correct. Here is a good page on the topic: https://www.thedrive.com/maintenance-repair/39173/dielectric-grease

 

[billbass]

Do not put dielectric grease on the battery posts or cable connections. Dielectric grease is an isolator, in that it does conduct electrical current. After your connections are made with clean dry components, then coat them with a corrosion inhibitor.

Dielectric grease IS a “corrosion inhibitor”. It inhibits corrosion by creating a shield of the elements (oxygen, water, and or salt) from the electrical connectors, just as a paint acts to keep something that deteriorates from whatever are the corrosive environment. You should put the dielectric grease on every contact surface and you can also coat the exterior of every connector with dielectric grease. That’s one of its prime purposes in life. It is not used as a lubricant. This is a very helpful website about the topic. https://www.thedrive.com/maintenance-repair/39173/dielectric-grease

 

[billbass]

hence the "probably"... Most are off/1/both/2 now. many years ago there were off/1/2/both or 1/off/2/both which are a problem. Never go to or thru OFF with a motor running.
Also, we don't know if his switch is broken...


I sounds, from the first post, that the 1 battery was 9 volts at some point. He was running on Both before that. I would suspect the Batt 1 is bad, not charging or holding a charge. This could be from constantly being draw down by the stereo or something else when they are not on the boat. Eventually, it won't charge back up. Sounds like they replaced a battery once. Is batt1 the new one? The dealer would have looked for bad connections and a bad switch but maybe they missed something

step 1a Pull the fuse to the stereo and listen to the water and the seagulls
Step1 b Always turn the switch to OFF before you leave the boat. that way anything you left on won't kill the battery.

Step 2 Pull Batt 1 out and have it tested.

Step 3 Run on batt2 and verify there is no problem

Step 4 put batt 2 in batt1 position, switch to 1 and see if there is a problem

I am looking forward to seeing the report on your questions. This will tell a lot. Great analysis questions.

 

[Halfhitch]

I think he just accidentally left out the word “not”. I assume that you meant to say above that dielectric grease does NOT conduct electricity. That would be correct. Here is a good page on the topic: https://www.thedrive.com/maintenance-repair/39173/dielectric-grease

Yes, I meant to say not conductive. I edited it to show correct intent.