Instal fuze block to battery or to starter?

[kac215]

I have a 20 footer with a mercruiser 5.7. I am removing old fuze block and all wires related to it (bilge, blower, nav/anchor lights, courtesy light, horn, depth finder, and stereo). The current block is under the dash easily accessible. I am not messing with the gauges or tilt/trim wires. I am doing this because when the boat was reupholstered a few years ago the wires were cut and spliced back together poorly and in some areas that aren't easy to get to in order to properly repair; plus I'm ocd and in need of a good boat project.

So, right now the fuze panel gets power from the starter I assume and I'm not sure where it is grounded (the boat is getting the carb rebuilt right now so it isn't at home). I only hook up one positive wire from the battery to the starter and one negative wire from the battery to the rear of the block. My question is if I should install this new panal like it is? Or if it is better to run positive and negative wires straight to the battery this time?

 

[GA_Boater]

I would wire the fuse block the same as it was originally. It saves the expense and trauma of trying to route a new positive and negative to the battery when you already have them. The starter isn't the voltage source, it's only a convenient tie point to the battery. The positive terminal on the starter is connected directly to the battery positive post.

 

[kac215]

Great! That is kind of what I wanted to hear. Again, I can't look under the dash right now because the boat isn't here so I have a few other questions:

Is the ground for everything under my dash (gauges and fuze block) coming out of the mercruiser engine harness?

How can I check to see if I have sufficient gauge wires to run my accessories? I do have a stereo amplifier that was installed by the po. It is getting power from the fuze block. I've never blown fuzes before (7 years) but since I am running wires anyway I thought I should make sure I'm doing it safe.

I want to do a clean wiring job and was thinking about using what I think is called a terminal block. I would run each wire from its source (bilge, blower, ect.) to this connection block under the dash and then from this connection block to its switch or fuze on the fuze block. This would be solely for the purpose of clean wire routing. Is this ok or not?

 

[GA_Boater]

Great! That is kind of what I wanted to hear. Again, I can't look under the dash right now because the boat isn't here so I have a few other questions:

Is the ground for everything under my dash (gauges and fuze block) coming out of the mercruiser engine harness? Most likely.

How can I check to see if I have sufficient gauge wires to run my accessories? I do have a stereo amplifier that was installed by the po. It is getting power from the fuze block. I've never blown fuzes before (7 years) but since I am running wires anyway I thought I should make sure I'm doing it safe. It's probably fine, but I'll let one of the more knowledgeable Sparkies handle that.

I want to do a clean wiring job and was thinking about using what I think is called a terminal block. I would run each wire from its source (bilge, blower, ect.) to this connection block under the dash and then from this connection block to its switch or fuze on the fuze block. This would be solely for the purpose of clean wire routing. Is this ok or not? Don't forget that every connection you add is a potential source of trouble. Adding a terminal block adds two possible points to each wire for corrosion, a notorious problem causer in boats..

As I said earlier, I would keep it as it was wired originally. How much power (wattage) is the amp? The Sparkies will want to know that

 

[kac215]

Great thanks! I'll check the amps' wattage when I get the boat back. If I think it is too much I think I'll add a small deep cycle to run just the stereo and put under the helm where the stereo and amp are. This wouldn't be a bad idea anyway. I may have not had a problem in the past because it's barely ever on anyway; but if it's there, I want it installed correctly. Thanks again!

 

[Silvertip]

Why add another point of failure (terminal block) when it isn't needed? You seem, to be looking at a circuit in reverse. Power enters the panel from the source which is the positive terminal of the battery via the starter in your case. At the panel one end of each fuse is fed by the positive bus. The other end of each fuse is where the wire connects that feeds the switch that it controls. The other side of the switch goes to the load (light, bilge, radio, or ???). Ground terminations for accessories may be at the fuse panel. Some have a ground bus and some don't. If yours does, accessories at or ahead of the fuse panel (toward the bow) can be grounded at the panel. Those at the rear of the boat can be grounded at the engine block or the negative terminal of the battery. There is no need to run an accessory ground wire all the way to ground bus on the fuse panel only to have to run all the way back to the battery via the engine harness.

If the fuse panel doesn't have a ground bus, then one can be added to accommodate accessory ground wires. That bus must then make its way to ground at the battery via the engine harness ground or a separate ground. Since your boat was wired properly at one time, use whatever scheme was used.

 

[kac215]

Ok. That makes more since. The accessories at the stern (in my case, stern light, blower, bilge, and courtesy light) are grounded on a neg. bus somewhere at the stern. So I just need to send the positive wires to the helm. The ground is sent to the helm via the engine harness for the voltmeter and then jumped to the gauges and the fuze block where helm and bow accessories can be grounded. Am I seeing this correctly? I'm laying out a simple diagram on a spreadsheet before I get to this. I plan on making the harness then installing it. It's easy to get wires where I want them in this boat but I want all these bundled together and the old ones out. Terminal block idea is out of my head now.

 

[Silvertip]

What you seem to be proposing should work, but I would verify the size of the ground wire in the engine harness. That wire may not have been sized to use as a "boat ground" but rather only as the ground for the instruments which draw very little power. Keep in mind that whatever size wire you use for the positive feed from the engine or battery, you must use the same size size or larger wire for the negative. Therefore the caution on using the engine harness ground for the entire boat.