Kevin,

The short story…

I’m upgrading the stereo in my 1988 Sea Ray 230CC. I’ve purchased most of the components:

• MB Quart WM1-head unit,
• 400W Pyle 4ch amp,
• 200W Pyle 2ch amp,
• Two 8″ Clarion subs,
• Six 5.25″ Polk coax speakers,
• MB Quart wired remote

If you are scratching your head over the equipment choices, I’m doing this on a tight budget. Was given the head unit (used), picked up an amp and two subs for fifty bucks locally and trying to make most of the rest work in the existing holes except for two of the 5″ speakers and subs.

I’ve installed the Head Unit where the old Sony am/fm cassette was in the cabin in order to “reuse” the hole.

I need some help in the boat wiring department. In doing much research I’ve come across some contradictions in how and where to install some things. Some recommend installing the amps close to the battery making shorter runs of thicker gauge cable and fusing. But that would require long runs of RCA cables and poses issues with ventilation. I want to mount the amps under the helm right next to the head Unit.

Here are some assumptions:

• Amp draw for 400W max amp: 400/14.4=27.8 amps
• Amp draw for 200W max amp: 200/14.4=13.9 amps
• Amp draw for HU. 45W/chX4 max: 180/14.4=12.5 amps
• Distance from boat helm to battery: approx 14 feet
• Planning on using 4 gauge tinned marine electrical wire for both power & ground

Here are some questions:

1. I would like to install a fuse block in the area with the amps and HU. I’m thinking 4 gauge power (14 feet) from the battery to a fuse block and then 8 gauge to each of the amps. I could also run an 8 gauge to the HU or run the HU power and ground to the “factory” fuse block where the old Sony is wired into.
2. Many recommend grounding the HU and the amps directly to the negative battery terminal (due to noise). Could I mount a marine electrical ground bus with a 4 gauge wire to the battery and run 8 gauge grounds to the HU and each amp?
3. Many recommend an in-line fuse of the power wire within 18″ of the battery. That would mean an inline fuse on the 4gauge, fuses for each component at the fuse block and the HU and each amp has their own blade fuse on the unit themselves. Is that overkill? If in line fuse is recommended, what size, 80 amp?
4. The old Sony had a black wire for power and a Red wire for power and a ground wire. The New MB Quart has a Red wire for Power, a yellow wire (memory power), blue wire (amp power) and a ground. Most recommend the Yellow wire connect(fused) to the live side of the battery switch to save memory functions, but I’m not so sure I need that feature. Planning on mostly listening to CD’s and Ipod. Not sure if I should splice the MB Quart’s red wire to the wire going to the old Sony’s black wire or red wire.
5. If I install a fuse block (power) and a distribution block (ground), should I install them with some extra spaces for future electronics like a GPS/Fishfinder? There are still a couple of spaces on the Factory fuse block that the Sony is connected to now. (that panel has power on one side and ground on the other)
6. There are four original 6″ speakers (old, cardboard Audiovox). It looks like the original speaker wire was 18 gauge. I have to run new speaker wire for the two additional speakers and the two subs. My estimate for the wire, due to the long run is 12 gauge wire. I plan on using marine duplex wire. Should I go through the trouble of re-wiring the four original speaker holes as well? It’s very tempting to just mount the new Polks in the existing holes and plug them in.

I’m sure there’s more, but I’m down to the “ordering wire” stage.  Tinned marine electrical wire is crazy expensive and I want to do it right the first time.

Thanks for all/any help.

Don

Hi Dave,

I like the “short story”!

Here are my recommendations for each of your questions:

1. Add the fuse block with dedicated power only for the stereo and amps.  Do not use it for any other components.  Add circuit protection at the boat battery switch or boat battery wiring.
2.  I would add a new, stereo ground block under the helm and only use this for the the stereo and amps.  Combining it with other components may add noise.
3. Most amps have circuit protection on board.  The fuse at the battery is to protect the wire.  If you used an 80 amp at the battery and 4 awg to all amps, then you would not need to have circuit protection in each individual leg.  When you step down the wire size at the distribution point, the wire becomes the fuse because it will burn up before the 80 amp breaker.  The official rules for circuit protection location are, 7″ from the source of power but up to 72″ from a direct battery connection if the wire is contained in a sheath or 40″ from a secondary location (battery switch) if the wire is contained in a sheath.  My opinion is, the farther away, the less safe the system.  Put is as close as possible to the battery or switch.
4. If you don’t really care about the stereo memory wire, don’t connect it.  More than half of the dead boat batteries can be associated to stereo memory wires.
5. I would not.  They will cause extra noise (transducer and vhf microphone clicking).
6. If I were the speaker wire salesman, I would say “Absolutely replace the wire.  Use 10 awg gold plated ,Monster Cable.”  If YOU go through the effort of replacing the wire, YOU will probably perceive a difference but nobody else will.

Good luck with your marine wiring project.

We will post pictures if you send them,

Kevin