Engine/fishfinder trouble

[MurphyAtkins]

Guys,
Got a problem with my GPS system and hoped someone out there may have the answer......

When I start out on a trip if I turn on my Humminbird GPS/fishfinder system the boat engine practically dies on me; forcing me to open the throttle to maximum and then the boat crawls along with the engine laboring. The moment I turn the GPS off the engine fires up and the boat takes off !!!!

The battery is the original I got the boat with 2 years ago, so it may be that it isn't holding enough power ??

Something which tends to confirm this is that the Fishfinder display is practically blank when the engine isn't running, which it never used to do when I 1st bought it. Also, after the engine has been running steady for 1/2 an hour or so the GPS can then be switched on with no effect, which makes me think the battery is taking some power.

I also thought about a short somewhere, or the alternator on the engine may be packing-up

I know that the cheapest option is to go to Halfords and buy a new battery, which I will do as a matter of course, but it would also be nice to know that there isn't some other cause.

Cheers - Murph

[paul mc]

Hi
Is the outboard an electric or manual start.
I ask because if the battery has enough power to start the engine it will probably be ok.
Have you a multitester to check the voltage accross the battery terminals take one reading with the GPS on and another with it off.

[kenp]

Battery u/s. The engine is trying to supply full power to the gps and not enough for itself.

[Bob]

Hi,
why not try a seperate Battery for your gps ?, a Leisure battery as used in caravans etc should power your gps for ages without needing charged, but would be of no use to turn your engine over, a deep cycle leisure battery can be bought for about £30-35 ish, and should be ok for marine use...just a thought

Bob.

[MurphyAtkins]

Hi Guys,
Thanks for the replies...I guess I will have to pay for a new battery.
I always carry a spare with jump leads when I'm out; also use the spare to power a car spotlight at night, which is brilliant (excuse the pun) when trying to land and unhook fish at night.
I will also see if I can find a mate with a volt meter to test the output with and without the Fishfinder on.

Cheers - Murph

[malroy]

Your engine supply battery needs to be a heavy duty type car battery, where it is not a deep cycle one. They are intended to be maintained in a continually topped up condition.

If you have room, fit a 2nd deep cycle leisure battery (85 amps min) and keep it on a seperate circuit from your engine supply.

Use it to power all you auxillary electrics, i.e. GPS, VHF, sounder, Nav lights etc.

I have found the best way to keep it charged is to fit a solar panel on your cuddy roof if you have one. It needs to be 5 watts minimum and have a diode to prevent reverse drainage/charging at night.

I fitted one 2 1/2 years ago and have never yet had to recharge it during the operating season.
I have a volt meter on its that allows me keep my eye on its level.

In an emergency, having a 2nd battery (with the same fittings to your engine unit) makes sense in that you can physically swap them over to get you out of a fix. Most 85 amp or over leisure batteries will crank your engine if kept in a good state of charge - depending on your engine size.
You may need more amps if over 70-80 hp.

I take both my batteries off the boat from December till March when winterising and charge them every 3 wks or so.

[cliffnorry]

Befor you get a new batterie, check to see you have not got a short betwen the batterie and the fishfinder, or you could be wasting your money, good luck.