Questions about grounding (DC only)

[Slide]

I have a 1987 Sea Ray Pachanga 22 with aftermarket 502 power. It has a dual-battery setup with a manual switch - the batteries are set up remotely in a small locker (was originally a cooler) at the center of the boat right by the helm. I bought it last year and noticed some electrical goofiness - power trim dims the lights and kills the stereo is one issue. I plan to go through the whole electrical system carefully this spring, since I plan to add a lot of new electrical accessories including a new stereo and VHF radio. I'm decently experienced with electrical systems having fully removed and replaced the system on my Hydrostream with an outboard motor but I am inexperienced with I/Os in this department.

Assuming my 502 has a stock alternator it should be giving me 65 amps, way more than enough to run all the stuff on the boat currently (essentially just lights, I don't use the stereo because it sucks). I'm thinking that to start I need to fix the dimming issues by replacing the main battery leads ("Big 3" in the auto world). The runs are long and the cables don't look to be very heavy gauge. My question is, how is an I/O grounded? Is there another lead I should be replacing besides the two main battery leads? I have read that I/Os are grounded to a bus near the engine block, is this an area I'll need to track down?

 

[UncleWillie]

Re: Questions about grounding (DC only)

If the battery is at the center of the boat with leads running aft, any large current draws (Trim!) are going to produce a nominal voltage drop on both leads, coming and going.
If your electronics/Fuse Panel is connected to the far end of these leads instead of AT the Battery, they will see the voltage at the rear of the boat and NOT the battery voltage which may be a volt or so higher. (Dimming)

If the cables are used to start the engine, #2awg may only be marginal at best. What Engine? What wire size and length?
Separating the Electronics/House loads from the Engine/Running loads on different batteries would reduce the problem.

 

[Bondo]

Re: Questions about grounding (DC only)

My question is, how is an I/O grounded? Is there another lead I should be replacing besides the two main battery leads? I have read that I/Os are grounded to a bus near the engine block, is this an area I'll need to track down?

Ayuh,..... The battery ground goes to the motor's Block, no buss bar,...

 

[Slide]

Re: Questions about grounding (DC only)

If the battery is at the center of the boat with leads running aft, any large current draws (Trim!) are going to produce a nominal voltage drop on both leads, coming and going.
If your electronics/Fuse Panel is connected to the far end of these leads instead of AT the Battery, they will see the voltage at the rear of the boat and NOT the battery voltage which may be a volt or so higher. (Dimming)

If the cables are used to start the engine, #2awg may only be marginal at best. What Engine? What wire size and length?
Separating the Electronics/House loads from the Engine/Running loads on different batteries would reduce the problem.

It is a dual battery setup with a dedicated starting battery and dedicated house battery. I was planning on going 1/0 AWG minimum for the leads. I'll have to do some sleuthing to find out where the house circuit panel connects to the system.

 

[Slide]

Re: Questions about grounding (DC only)

Ayuh,..... The battery ground goes to the motor's Block, no buss bar,...

Where is the motor then grounded to? Transom plate, or somewhere on the hull?

 

[Bondo]

Re: Questions about grounding (DC only)

Where is the motor then grounded to? Transom plate, or somewhere on the hull?

Ayuh,... The Battery to Motor ground, grounds the electrical system,....

Any accessory grounds go to a buss bar, which is grounded to either the battery, or the motor's block,....

Boats also have a Bondin' system, in which All metal parts, 'n the fuel system are tied together by Bondin' wires,...

 

[UncleWillie]

Re: Questions about grounding (DC only)

It is a dual battery setup with a dedicated starting battery and dedicated house battery. I was planning on going 1/0 AWG minimum for the leads. I'll have to do some sleuthing to find out where the house circuit panel connects to the system.

I suspect the Power trim is wired to the House Battery. Moving it to the Starting battery would solve the Dimming problem. Presumably you are only trimming when you are moving so the engine will be running.

Where is the motor then grounded to? Transom plate, or somewhere on the hull?

As BONDO stated, The Motor is Grounded to the Battery. The Hull is not grounded, especially a Fiberglass hull.

 

[bruceb58]

Re: Questions about grounding (DC only)

You need to figure out where all the power of your accessories are connected to in order to do real trouble shooting

I had an issue where operating my trim was causing my engine to die. The problem was a corroded connection down at the starter where the feed to all accessories including ignition and the trim is fed from( I do not have a separate house battery). The voltage drop across that connection when I had a high current draw at the trim pump caused the ignition to cut out.

Same exact thing can be caused by a bad ground connection.