thinking of running mobile 1 in my engines , how often should this be changed from current valvoline vr1 racing 40wt. ?

I ran Valvoline VR 40 and use to change it about every 25 hours. If I ran the boat hard I would change it after that run.

I have the same setup you do Tony. I go every 20-25 with Mobil 1 15W50.

for as much as you use your boat every 4-5 years .... Just kidding, I change oil in the HO once at the end of the season, usually about 50-60 hours with Mobil 1 15-50...

That's the exact same as me