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Recently bought a brand spanking new 3.8 metre aluminium dinghy and a new 15hp yamaha to match (model 15FMHS / 15FMHL i think- thats a portable 2 stroke).
My question is about rigging up some spotlights so i can go garfish dabbing. The motor has a 12v power socket to draw from the onboard alternator (12V-80W (6A) so the manual tells me).
What can be done for my application? Should i rig up a battery that can be charged from the motor while it is being used, or should i just buy a car battery and charge it with an ordinary mains battery charger out of the boat?

Can anyone speak from experience???

Worked for years in commercial boats with yamaha and my experience is put a battery in the boat and charge it from the outboard motor. spotlights while fishing will flatten the battery very quickly, if not charged up as required. I dont know what the new motors are like but the older ones didnt put out much charge until the motor had a few revs up above idling, but once on the move did a good job of recharging quite quickly. I did read somewhere that yamahaand others had overcome the low charge problem on their newer motors when at idle. Make sure you use a Marine grade deep cycle battery.

Why a marine grade deep cycle?
Should i just cut the crap and use an isolated system that uses a car battery and then charge the thing on-shore? I will only be using it a dozen times a year.

If your only going to use the thing occasionally, then just throw a car battery in when you are hunting gar and charge it in your shed. Extra weight in a small tinny can make a huge difference to how it handles, you dont want to be lugging it around every time you go out if its not being used.

You want a marine grade battery for starting, you dont need it for running a spotlight though. They are built tougher with heavier plates so they can handle the hammering they get in a planing hull. Worst case is your car battery will eventually collapse and you wont have your spotlight.. big deal.


If you want wire a permanent install into the boat then think about it this way. If you have a 100W spotlight, 3 5W nav lights and say a 10W fluro tube lighting up inside the hull, then your max load is 125W. at 12V thats about 10A.

Your charger will output 6A PEAK. so if you run your lights flat out for 1 hour, you will need to run the engine at full RPM for 1.67 hours to get teh battery back to where it was. Now realistically you will only turn the spotlight and deck light on intermittently, so your 6A charger is actually pretty useful.

I had a similar setup to this in my last tinny, however i also had a sounder and car stereo wired in. I used a small motorcycle starting battery and found that i never needed to charge it as the outboard always kept it topped up enough.

Thanks guys,
I reckon for now i will just use my 6A-hour portable battery pack and the 50W spottie that i use for spear fishing. If I get around to getting some serious power gear into the boat I will go the full monty with a deep cycle battery etc all wired in.
Thanks again.

One thing to remember about rigging lights on a boat, dont use the hull as the ground/negative return. All those spare electrons running about will decay your boat. Always run a propper negative from your load back to the battery.

Nice point, i will keep it a totally isolated system anyway as it is a manual start and i dont have/need any nav lights.

julian wrote: i dont have/need any nav lights.

Mate, you *need* nav lights, regardless of where or when you think you'll be fishing...

Have a read of this...
http://www.ausfish.com.au/forum/YaBB.cg ... 058057/1#1

$20 will get you some nav lights.

hey Ben, what is your user name on ausfish? Mine is Jack_attack.

I agree with the last comment Nav lights are a must. They are a must,to be used in any instance of limited visibility. eg rain fog smoke even in the middle of the day. I used to be a boating/fisheries inspector, the amount of poeple ew ran across and sent home FOR THEIR OWN SAFETY AND OTHERS because they thought they didnt need nav lights was unbelievable. As the man says $20 for lights is a dam sight cheaper the the fine youll cop if caught out without them!

BYB-01 wrote:hey Ben, what is your user name on ausfish? Mine is Jack_attack.

Ausfish - BenatCoffs
Sportsfish - Ben78
Fishnet - Ben78

Don't post much at Ausfish, just read - they tend to be far too catch and release oriented, should have seen the shit I copped cos I kept the first cod I ever caught!!

I find the other two to be about the sport, but a feed is a suitable end result too.

Well I think you have convinced me. Full electric setup including navigation lights will find its way into the boat over the next few months.
Cheers for the input fellas.