350 SLX Mercathode Fuse Location

[GaryG]

The 2017 350 Mercruiser manual recommends checking the 5 amp inline fuse if the Mercathode LED is off but I can't find the fuse. The red power wire goes off into a huge bundle and I have no clue where it goes. Can anyone help me locate the fuse?

 

[Steve in Minneapolis]

There is a fuse block diagram on the left side of your photo. Is it on there?

 

[GaryG]

Steve, no it's not in the fuse box on the engine, however, I did finally locate a fuse. I first found a fuse box forward of the starboard engine (see photo). This box had two 20 amp and one 5 amp fuse with nothing indicating what they went to. I pulled the 5 amp fuse to see if the Mercathode LED would go out on the starboard engine but nothing happened. I pulled one of the 20 amp fuses and the light went out. Then I took that fuse and stuck it in the position of the other 20 amp fuse to see if the light on the port engine would come on. It did not. After more searching, I found an identical fuse box forward of the port engine. I opened it and discovered one 5 amp fuse and nothing else in the box. I took a new 20 amp fuse and installed in the C location (same as the starboard engine) and voila, the LED light came on for the port engine. At least the LEDs are now indicating that both systems are operating. I marked the lids of both boxes for future reference. So, I never found the inline 5 amp fuse noted in the manual but I did find a controlling fuse for one engine. Now I'm left wondering why there was no fuse for the port engine mercathode system. During all this I did find a burned out 10 amp fuse on the bilge floor.... Also why are there two 20 amp fuses in the box for the starboard engine and only one for the port engine? Why doesn't Sea Ray bother to mark the fuse box covers to indicate what the fuses are for? Some mysteries may never be solved!