I guess I can trace the current yellow hose going to the flame arrestor and I am thinking I can T into that if desired.

I pull my impeller when I winterize my boat. It allows me to drain the lines and oil cooler completely. I have a floor drain in my garage so I drain everything inside. I do it in place so I don't have to disconnect the fuel lines. I use a little mighty vac to suck out the gear lube when I change it. To put the impeller back in I use a hose clamp to compress the vanes and soap to lube it up. It's super easy and doesn't take much time at all. It takes less than 30 minutes to re-assemble in the spring and re-tension the belt. Of course I do have a single so plenty of access.