Thruster fuse

K

knotflying

Well-known member
Joined
Jul 25, 2010
Messages
6,014
Fluid Motion Model
C-28
Hull Identification Number
FMLT2731J011
Non-Fluid Motion Model
25' Parker & 246 Robalo Cayman
Vessel Name
http://illusionsmikeandjess.blogspot.com
I just had to change my rear thruster fuse. The fuses I have are 150 amp. However when I was looking in the Sidepower manual it states that the amperage draw on the smallest size thruster, which I assume we have, is 195 amps. Anyone have any input on this? I would assume a larger amp fuse would not have some of the issues I have read about regarding fuses getting weak and blowing. I would assume the wiring to the thrusters, should be sized appropriately as well to take the 195 amp draw.

Any comments?

Mike Rizzo
 
Hi Mike,

A 150A fuse will not blow at 150A, in fact it will not blow at the rated thruster draw of 195A. The speed at which a fuse (or breaker) opens depends on the amount of overload, at very high overloads they will open quickly. At moderate overloads it can take a number of seconds/minutes to open.

Look at the Blue Sea blow delay curve chart for an ANL fuse: https://www.bluesea.com/products/5127/A ... _-_150_Amp

You can see it will work indefinitely at more than 125% of rating. At 400% it will blow in about 1 second.

The 150A fuse is the value recommended by Side Power and is appropriately sized. A larger fuse may fail to blow in a fault condition and be a fire risk.

I changed my rear thruster fuse this past summer, not because it failed but because it became heavily corroded. The fuse element itself was also corroded, this would lower the current at which it would blow.

Howard
 
Thanks for your comments as well as an e-mail I received from Andrew explaining the situation. I guess the fuses blowing are related more to corrosion than to excess amperage.
 
This 150 amp fuse is commonly used in large "rock" amplifiers. It is readily available gold plated, see Ebay. This will stop your corrosion problem and will probably be much less expensive than when purchased as a boat part.
 
If you do buy the 150 amp fuses on Ebay you may find the slots too small to fit over the posts. You may have to file or grind the slots to a larger size before they will fit. You may want to do this before you actually need them.
 
Last Summer I had a problem with the rear thruster blowing the fuse. I had some aftermarket fuses that came with the boat from the previous owner that required the slots to be enlarged. These "new" fuses blew out also. I acquired the proper fuses from the Ranger Factory and haven't had a problem since. I have also done a much better job in painting the thrusters with anti-fouling paint.
 
The cheap fuses are questionable for thruster usage. We are depending on known and consistent overload characteristics for the fuse since a 150A fuse is used for a 195A load. Who knows what the cheap fuses are really rated for. I would not use a larger fuse, such as 200A, because it would take considerably more than 200A to blow and you would have a fire risk.

See the link I provided for the Blue Sea ANL fuse blow characteristics based on current and time.

I have not had any problems with the Side Power fuses purchased from Ranger Tugs. I have replaced one in 4 years and this was a precaution because the fuse link had corroded. I was concerned it would fail at a lower than spec current due to the corrosion.

Also make sure the terminals and connections are very clean and corrosion free. Mine were becoming corroded/oxidized. I disassembled the fuse holders, cleaned all the pieces, terminals, and ends of the fuses with a scotch-bright pad. I protected them with electrical terminal grease (NO-OX-ID A Special) before re-assembling.

Howard
 
Change the fuels out and replace it with a breaker, never have to worry again about having a fuels blow on a trip.
 
Get the "real deal" from Ed Ruff in Ft Lauderdale or Ranger and then install exactly them exactly like Side Power instructs. Get the installation instructions from Side Power. Its cheaper and you don't have to file anything and it will work.
 
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