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Old 03 May 2011, 16:35   #1
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Country: UK - Scotland
Town: Aberdeenshire
Boat name: Sula
Make: Ribcraft 4.8m
Length: 4m +
Engine: Tohatsu 60hp + aux
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Wiring a RIBcraft 4.8m

After picking up my new boat last year, I'm slowly crossing off the jobs still to do, and the dreaded electrics is last on my list. The boat has under-deck trunking, so all the cables to and from the engine are out of sight. The entry/exit point is within the console for connection to the battery, etc.

If anyone can point me in the general direction (regards wiring) I'd appreciate it.

The engine is a 2006 Tohatsu 60hp (2-stroke) PTT. It's now mounted. Throttle and gear shift cables still to install - that's for this weekend, along with fuel connections.

What I plan to install:
1/ 12v battery in battery-box secured in the console
2/ Fit Tohatsu trim guage and tacho (I'll cut holes in the console once I've tested them)
3/ Extend battery cables (current cables are too short)
4/ Install battery isolator switch
5/ Install rocker switches/fuse panel
6/ Fit Perko light pole
7/ Fit DSC VHF radio and antenna

The trim and tacho gauges look straight forward as they have wiring looms and connect either to the throttle control or direct from the engine.

Where do I start? From the 12v battery, do I connect directly to the battery isolator switch, and from that to the fuse panel, etc. Also what gauge of wire do I need.
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Old 03 May 2011, 17:01   #2
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First of all let's not make things too complicated, outboard wiring must be a separate job.

From Outboard you generally need to connect it directly to your Battery (or if you have Isolator) for Positive and Negative is connected in the same way but just directly between the battery's negative point and the outboard.

You must check the wiring diagram for the outboard to make sure there is a fuse already built in. If not, you must check the starting current and put a High Amp fuse between the positive connection. That depends on the starting current, DO NOT install a very High Amp fuse as it could possibly damage your outboard and again if you install a low amp fuse it could just burn every time you try to start the engine (I assume it is electric start??).

Once you have done the wiring for the outboard, CHECK that the outboard is charging the battery. You need a Voltmeter. The battery voltage must read about 11.9-13V before starting the engine and about 30sec after the engine is started it should go about 14V.

So far you have completed the wiring for the outboard.

Then you need a Distribution Terminal for VHF, GPS, Nav Lights etc.. One Thick High Amp Cable should be connected to your Battery's positive node (or Battery Isolator) and then connect it to the terminal. Other electronics must be supplied from the Terminal.

You must have fuse between Positive connections of ALL electronics and Lights etc. and the Terminal. Most of these devices come with an appropriate fuse in their package so use exactly that fuse.
For negative connection of the electronics you again need another terminal. Same procedure but without the in-line fuse. DO NOT connect the negatives to the battery's negative node as it will be messy.

If you have expensive GPS or Plotter etc. with LCD you may consider a Voltage Regulator as in case your outboard is overcharging the battery it does not damage those gadgets.
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Old 03 May 2011, 18:10   #3
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Country: UK - Scotland
Town: Aberdeenshire
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Make: Ribcraft 4.8m
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Thanks Vandad.

Quote:
From Outboard you generally need to connect it directly to your Battery (or if you have Isolator) for Positive and Negative is connected in the same way but just directly between the battery's negative point and the outboard.
Forgive me if I'm recapping here - but it's just so I'm 100% sure. I am planning to connect an isolator switch between the outboard and the battery. The (+) cable from the engine goes direct to the isolator. And the (-) cable from the engine goes direct to battery (-) terminal?

Quote:
You must check the wiring diagram for the outboard to make sure there is a fuse already built in. If not, you must check the starting current and put a High Amp fuse between the positive connection. That depends on the starting current, DO NOT install a very High Amp fuse as it could possibly damage your outboard and again if you install a low amp fuse it could just burn every time you try to start the engine (I assume it is electric start??).
I've checked this. The engine has a 20amp inline fuse already installed.

Quote:
Once you have done the wiring for the outboard, CHECK that the outboard is charging the battery. You need a Voltmeter. The battery voltage must read about 11.9-13V before starting the engine and about 30sec after the engine is started it should go about 14V.
The battery reads 13v just now prior to starting. I'll double-check it again once it's running.

Quote:
Then you need a Distribution Terminal for VHF, GPS, Nav Lights etc.. One Thick High Amp Cable should be connected to your Battery's positive node (or Battery Isolator) and then connect it to the terminal. Other electronics must be supplied from the Terminal.
What are we talking about here, 45amp 10mm wire for example? So connect this wire from the (+) battery terminal to the (+) terminal on the isolator?

Quote:
You must have fuse between Positive connections of ALL electronics and Lights etc. and the Terminal. Most of these devices come with an appropriate fuse in their package so use exactly that fuse. For negative connection of the electronics you again need another terminal. Same procedure but without the in-line fuse. DO NOT connect the negatives to the battery's negative node as it will be messy.
I'm assuming this is where the fuse panel and rocker switches comes in? How does the fuse panel connect? Do you run a high-amp wire (+) from the fuse panel to the battery isolator (+), and then run another high amp wire (-) from the fuse panel direct to the (-) battery terminal?
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Old 03 May 2011, 23:30   #4
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Quote:
Originally Posted by Vandad View Post
You must check the wiring diagram for the outboard to make sure there is a fuse already built in. If not, you must check the starting current and put a High Amp fuse between the positive connection. That depends on the starting current, DO NOT install a very High Amp fuse as it could possibly damage your outboard and again if you install a low amp fuse it could just burn every time you try to start the engine (I assume it is electric start??).
Are you sure about that?
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Old 04 May 2011, 03:42   #5
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I would never fit a fuse in the starter feed and would also never extend those wires but fit new one piece ones.
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Originally Posted by Zippy
When a boat looks that good who needs tubes!!!
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Old 04 May 2011, 05:45   #6
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Here's my fuse panel

At the risk of being shot down in flames, here's my fuse board (DIY in 5.45m Ribcraft) .

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The actual fuse-box cover is removed. This one covers all the non-engine aspects only, i.e. radio, sounder, lights, bilge pump, compass illumination, fuel gauge and possibly something else I can't remember right now. The car-type fuse holder came from Halfords, and the positive and negative bars came from IIRC Index Marine. I have no idea why I used differing length bars. 2A blade fuses aren't the easist to find; obviously I used 3A! Proper ratchet crimps make more reliable crimps on the spade connectors. And those square stick-on cable tie attachments work well to keep things tidy. Arm yourself with hundreds of small cable ties - I ended up wasting lots as the loom sizes grew during fitting. The power supply to this board is taken from the left side of the bars to the battery - except the positive lead is 'split' by one of those console mounted 10 plastic key isolator thingies which has easily been the least reliable part. I later made a bridging lead to use on those days it decides not to make contact. With hindsight the main power supply cables could probably have been beefier. All finally sprayed with some Halfords damp seal type stuff, and apart from the isolator, all has worked well for 10 years or so. Next time around I'd strive to be even neater and spread the stuff out slightly more. I'm sure there's much better out there - but it's a start ...
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Old 04 May 2011, 08:34   #7
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A better but more expensive solution is to use the heatshrink connectors that have hot glue in them - it seals the end of the wire. The wire we use is marine grade which doesn't go black in time and will outlast the plain copper wire many times over.
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When a boat looks that good who needs tubes!!!
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Old 04 May 2011, 10:28   #8
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Country: UK - Scotland
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Make: Ribcraft 4.8m
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Quote:
Originally Posted by Neil R View Post
At the risk of being shot down in flames, here's my fuse board (DIY in 5.45m Ribcraft).
Great stuff.
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Old 04 May 2011, 13:08   #9
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Quote:
Originally Posted by Cookee View Post
A better but more expensive solution is to use the heatshrink connectors that have hot glue in them - it seals the end of the wire. The wire we use is marine grade which doesn't go black in time and will outlast the plain copper wire many times over.
Is the Marine cable ' tinned', do you use multi strand or single strand cable?.
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Old 04 May 2011, 16:46   #10
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As Vandad says, you want to keep the outboard cables independant from the 'domestic' supply. You probably need 25mm2 cable at most to feed the starter on the outboard. the longer teh cable run the larger the cable needs to be to avoid voltage drop. I would suggest a good battery switch (BEP or Hella Marine) in the positive cable somewhere near the battery. The starter draws a huge current so any smaller cross section of cable may get warm and reduce voltage supply to the starter. The negative cable will be unswitched and connected straight to the battery -'ve terminal. From the switched side of your battery switch you can then run a second cable to your fuse/distribution board. A 5mm cable would be quite adequate here given the short lengths involved and lower power requirements. Obviously the negative from the -'ve buss needs to be 5mm too. You can then wire each of your navigatin instruments to a separate fuse on the distrubution panel. All negatives will be connected to a common buss for convenience. Neil R's picture illustrates this quite well.

I always use multistrand tinned marine cable and good quality adhesive lined heatshrink connectors for the important items.

Photo shows my wiring half way through fit out
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