Hey Sealure

Fuses are designed to protect circuits against over current situations. For instance, when a shortcircuit occurs in a circuit, too much current flows and the fuse melts to protect the rest of the circuit. Fuses are relatively slow reaction devices because the fuse wire needs to carry enough current to heat it up sufficiently to melt the fuse element. Voltage transient spikes and surges are very quick changes in the supply voltage which happen at a much much faster rate than a fuse can react to.

In short, unless a voltage surge happens for a long enough time to cause an elevated current flow that is enough to blow a the rated fuse, a simple fuse in-line with the power is not enough to protect a unit against voltage spikes and brief surges that may be produced by alternators (fitted in the engines) or generators if the electronics are connected to the same battery bank.

I would always recommend using a voltage surge suppressor or, even better, a power conditioner to clean the supply up a bit and remove any spikes, surges or dips that are very often present in marine situations.

Good luck!

 Hey Paul

Power conditioners come in many sizes and power ratings (current ratings). You can use one small one for a particular piece of equipment, or a much larger one that can run an array of electronics. Intervolt make a decent range of power conditioners at different current ratings and prices to suit the installation.

Obviously, the higher the current rating of the conditioner, the larger the physical size, but a typical 7 amp Intervolt power conditioner can fit into your back pocket and isn't expensive, relatively speaking.

A larger 20 amp power conditioner can be fitted before a set of breakers that is used solely for house electronics is another way of doing things, but often I have also seen installations where one smaller conditioner was used for each piece of electronics that the owner wanted to protect. 

I'm surprised to hear you mention that you've never come across a power conditioner on a trailer because personally I encounter them on about 50% of the boats I see and I'd love to see more and more of them used. We'd all love a perfect marine electronics environment where there is a dedicated house bank of batteries separate from the engine starter batteries, but unfortunately, this isn't always the case. In these installations, in particular, I think a power conditioner is absolutely the way to go to protect one's investment in marine electronics.

Cheers

 Hey Paul

Power conditioners come in many sizes and power ratings (current ratings). You can use one small one for a particular piece of equipment, or a much larger one that can run an array of electronics. Intervolt make a decent range of power conditioners at different current ratings and prices to suit the installation.

Obviously, the higher the current rating of the conditioner, the larger the physical size, but a typical 7 amp Intervolt power conditioner can fit into your back pocket and isn't expensive, relatively speaking.

A larger 20 amp power conditioner can be fitted before a set of breakers that is used solely for house electronics is another way of doing things, but often I have also seen installations where one smaller conditioner was used for each piece of electronics that the owner wanted to protect. 

I'm surprised to hear you mention that you've never come across a power conditioner on a trailer because personally I encounter them on about 50% of the boats I see and I'd love to see more and more of them used. We'd all love a perfect marine electronics environment where there is a dedicated house bank of batteries separate from the engine starter batteries, but unfortunately, this isn't always the case. In these installations, in particular, I think a power conditioner is absolutely the way to go to protect one's investment in marine electronics.

Cheers

could u give us aname of a make or a link to some surge proteters suitable for sounders 3-5a barra

Hey Shark1

Without breaking any forum rules, I can highly recommend the Intervolt range of power conditioners. I have used these on many installations and they do the job nicely.

Google the name to bring up the website and you can view their range of power conditioners. There may be different brand out there though which a quick Google will probably reveal.

Cheers!

 I replaced it with a cheap after market reg and had nothing but problems with the engine shuting down turned out that the cheap reg was letting large spikes through causing my ecu to reset shuting the engine down .now I run a fcv 295 plus other electronics and have had no problems with my sounder so I would have thought that if the spike was large enough to fry the sounder you would have had some other symptoms or damage to something else aswell  

 Possibly, but not necessarily. 

I had a power failure at home last year where the power tripped out a few times in a minute and when it came back on the lights dimmed a few times and my TV flickered a bit. Everything survived except my PC power supply which cooked itself and I had to buy a new one. Electronics.....gotta love 'em! 

 Hey Sealure

Maybe it did, but it would have happened so quickly that I doubt you'd see it. Besides, GPS receivers use dampening and averaging when calculating positions and speed and a split second interruption in reception of GPS satellite data wouldn't affect operation.