Blade fuses in 190FSH

[Kahuna Khris]

In solving my recent electrical issues I came across several blade fuses that were a little confusing. They are opaque black blade fuses with 120 stamped on the back. Obviously they are not robust enough to be 120 amp fuses but I want to identify them to have some replacements on board should one blow. I have gone to several marine facilities and no-one has seen them before. There is one hanging from the main wire bundle running to the console electronics and another one in the circuit under the floor hatch over the gas tank. Black is the colour for 1 amp fuses but the 120 and general appearance of the blade fuse is unusual. Any comments?

 

[tek4fun]

Those are not fuses. They are actually resistors used for the CAN communications of the electronics. These are also not an 'off the shelf' item, meaning you would need to get replacements or back ups from Yamaha service.

 

[Kahuna Khris]

Thanks very much. I found no reference to them in the service manual and no one I showed, who was into boating and marine electronics knew what they were. How is anyone supposed to know? Are they unique to Yamaha boats and can you elaborate on CAN?

 

[Kahuna Khris]

Those are not fuses. They are actually resistors used for the CAN communications of the electronics. These are also not an 'off the shelf' item, meaning you would need to get replacements or back ups from Yamaha service.

Thanks again. googled CAN and got a quick lesson.

 

[Kahuna Khris]

So in continuing by resistor education, thanks to tek4fun, the 120 stamped on the resistor means a 12 ohm resistor. The first two digits of the stamped number are values and the third digit is a multiplier (not meaning 12 x 0 but 12 x 1 as the third digit is the number of zeroes after the number 1 to multiply the values by. Correct me if I'm wrong tek. So if I call Yamaha I'm asking for a 12 ohm bladed resistor.....correct?

 

[tek4fun]

So in continuing by resistor education, thanks to tek4fun, the 120 stamped on the resistor means a 12 ohm resistor. The first two digits of the stamped number are values and the third digit is a multiplier (not meaning 12 x 0 but 12 x 1 as the third digit is the number of zeroes after the number 1 to multiply the values by. Correct me if I'm wrong tek. So if I call Yamaha I'm asking for a 12 ohm bladed resistor.....correct?

I am glad that you are enjoying the chance to learn here. You are reading a little too much into the 120 stamped on the resistor. It actually means a 120 Ohm resistor. At the wiring end points of any CAN bus, there must be 2-120 Ohm resistors with one at each end. Sometimes, these are integrated into the devices themselves. There are some boats that have a resistor that looks the same but it is stamped with 1.2 k (1.2 kOhm). These are used for a different reason, generally in the lighting circuits. They are not for CAN. Do not get them confused, because it can be hard to tell the difference between the two.

For additional information. NMEA 2000 backbones in a boat is a type of CAN bus. It just follows stricter guidelines as set forth by the NMEA board. At both ends of the backbone for the NMEA 2000 there are termination pieces that are required to complete the backbone. These are also 120 Ohm resistors, but in a different form factor.

 

[Kahuna Khris]

I do like to understand the provess so will read your reference material. Thanks again.