I added a fuel/water separator to my center console boat.
The link to the unit I installed is below.
You may need to source the appropriate size fittings for your size fuel hose.
As always, use stainless steel through bolts to mount it.
I suggest that you follow the current path of the fuel hose and mount the filter receptacle in that path.
Remember to allow enough vertical clearance below the filter to allow you to remove it easily.
A little extra room will allow you to slide a cut off 1 gallon jug bottom under it to prevent spills while removing.
Walmart and Parafunalia often carry the replacement filters.
You can change it yearly or dump it out and reuse it until it gets rusty.
https://www.easternmarine.com/quicks...r-kit-802893q4
Oh, and Walmart for the battery but do add a solar charger!
EDIT:
My application was a 50 hp two stroke. You may want to call Mercury to verify that this filter has adequate flow for your 150 hp motor.