Installing new guages.

[toolsinbox]

I have ordered new guages for my 89 21 ft scarab. 454 ls6 engine, alpha outdrive. Currently the tach works, the fuel guage worksbut they are all different brand guages and look baaaaaad. I checked the fuse block and noticed one of the fuse holder was broken. No biggie as it was not being used but I want to replace the entire fuse block for a modern one. I want to rewire the entire helm and install second battery to run accessaries like sterio lights etc. I have no problem doing switch and second battery as I have done it before.

My question is once I get the battery switch and second battery hooked up what and how many direct power wires do I need to bring to the helm and what guage wire? Same question for the groung. Obviously I need to bring a power wire to the fuse block. What guage wire should that be? What components should be run through the fuse block and what should not be. How do I know what size fuses to run in each item. For example, I have an msd ignition that I am sorting out and have to correctly wire the key switch to shut off the engine. What size fuse do I use there?

Secondly the power trim works great I have a up down switch mounted on dash along with a up down switch that is on a wire coil that can be hand held. Dose the trim run through the fuse pannel or is it direct wired.

As you can tell I am a bit over my head with all this but I am determend to make this all work and look great. The boat runs like a dream I guess the previous owner didnt get to the wiring before passing away.

Any help here would be great

 

[mkast]

Re: Installing new guages.

As you can tell I am a bit over my head with all this but I am determend to make this all work and look great. The boat runs like a dream I guess the previous owner didnt get to the wiring before passing away.

You state "The boat runs like a dream", and you have determined that the wiring needs to be ...rewired by someone "In over their head"

 

[Bondo]

Re: Installing new guages.

what and how many direct power wires do I need to bring to the helm and what guage wire? Same question for the groung. Obviously I need to bring a power wire to the fuse block. What guage wire should that be? What components should be run through the fuse block and what should not be. How do I know what size fuses to run in each item. For example, I have an msd ignition that I am sorting out and have to correctly wire the key switch to shut off the engine. What size fuse do I use there?

Ayuh,... It's All about the Expected Loads....
You need wiring,+ fuses that'll carry the Expected loads, yet yeild when the load is too High, in amps(the Fuses, not the wiring)...

 

[Vex]

Re: Installing new guages.

Fuses are cheep. Just a suggestion..but start small and work your way up till they don't blow under normal operating mode. Unless of course you can find out what is actually supposed to be in there. Keep plenty of spares handy.

 

[toolsinbox]

Re: Installing new guages.

I understand that the wiring and fuses need to handle the load and the fuses need to kick when they are over loaded. That was not my question. My question was if anyone new what guage wire should be sent to the helm for a standerd fuse pannel ? to supply the .Running lights, docking lights, Temp guage, fuel, Tach, volt, trim, and the likes. I could add all these things up and figure it out but I asked here to possible save a bit of time. In addition I asked what else should go through a standerd fuse pannel, such as power trim, hydrolic engine hatch. Ignition, ect. I understand that there are wires that supply the guages from senders and those are seperate and the guage manufacture spells that out. As far as the running lights I will just add up the bulbs and arrive at the fused amperage needed, but all this comes from the fuse pannel.

I need power and ground to the helm and want to make sure I have the correct wire. I am not assuming the previous owner hooked any of this up correctly. The existing fuse block is old and in need of replacement, and some of the wires are brittle.

Is it propper to fuse the power trim at the helm?

Is it propper to fuse the power hatch at the helm?

I am calling on some experience that others have had wiring a helm. I dont want to buy and run wire only to have to remome it due to incorect wire type. What should be fused at the helm and what should not. If there is a web site, book, or drawing, I should be looking at please let me know. I have been unsucessful in getting a manual of any wiring info for my boat from the manufacture. It could be described that I am creating a new harnes for the helm. If I havent asked my questions clearly enough I appoligise.

Any help on this would be great.

Thanks

 

[QC]

Re: Installing new guages.

I moved this over to Electronics as this is not necessarily I/O specific and you'll get better help with the wiring questions etc.

I bought a set of surplus gauges from these guys. It came with a full wiring harness for a fishing toon or something. I've got like 20 breakers for everything under the sun (no fuses), also dash switches etc. Complete with Deutsch connectors, drop down leads, etc. etc. etc. All plug and play for a Mercruiser. If you cannot cancel your gauges maybe they have the rest of this stuff available too. That's what I'd do, splice in what you need, chuck everything else. Solved quite a few problems for my project . . .

 

[Blue Crabber]

Re: Installing new guages.

The fuse and wire size is determined by the amp load connected to it. Here is a formula that may help:

P/E=I

P = Power (you will find this rating in Watts on the info plate of the device)
E = Voltage (this will be 12 because that is the battery voltage)
I = Amps (this is the size fuse you will need. But just go to the next size up)

You will need to add the wattage of all items powered by this fuse before using the formula

Example: Navagation lights. Bow light is 10 watts and anchor light is 25 watts. Total watts = 35, then:

35 watts / 12 volts = 2.92 Amps

You would want to use a 3 amp fuse minimum. However, if the load is expected to be in use for 3 hours or more, you must multiply the answer from the formula by 1.25 Since the lights could be on for more than 3 hours, especially if anchored overnight the answer to the equation is:

2.92 amps * 1.25 = 3.65 Amps.

I would use a 4 amp fuse in this example.

Wire Sizes:

Wire also has an ampacity rating. Use a wire rated for at least the size fuse protecting it.

In the example above, a wire rated for more than 4 amps would be pretty small. Better to use a more common size wire. Bigger wire will not hurt anything as long as it can be properly fastened.

Hope this helps!