Steve, you need to run the wire through the same "rigging grommet" where your control cables, battery cables, main harness & fuel line enter the cowling. If you have a "rigging tube", that will be difficult enough.

If there is a molded rubber thingy with individual holes - all of which are already being used - its even more challenging. The NMEA cable itself should squeeze in, but first you've got to pass through the connector on the end.

One approach is to disconnect either the gas hose, or the ground cable, at the engine, then pull it completely back out of the grommet; now you've got an open hole to pass the NMEA cable end through. Then tape the two together and use the NMEA wire to pull them both back through the same hole. Soapy water or some silicone grease will help.

There is probably one or more clamp/cable ties surrounding/compressing the grommet, which you'll need to remove first and then replace to finish up. There will also be some kind of "hold down" bracket or little piece of cowling bolted over the top of the grommet - loosening or removing that may help give you clearance while you work

+1 one on fishing it through with some soapy water/silicone. It would also be a heck of a lot easier if you disconnect everything on the engine side - which would allow you to straighten out the rigging hose, rather than trying to pull things through a couple of bends.

I don't know if this is available for your engine, but for mine, I replaced the rubber grommet with an 'open' grommet that I got from SIM (I'm sure it's available elsewhere). MUCH, MUCH, EASIER.

Running motor cable on Yama

Thank you Dennis and Fair Deal. That makes sense. I wil take a look at both options.
Any ideas on where to get the generic grommet to replace the custom one?
Stevev

The SIM I mentioned above is SIM Yamaha.