It has been suggested in this form that I use ZDDP based oil to stop my oil consumption. Does anyone have any thoughts on this. Thank you

No opinion (or knowledge) on the ZDDP, but wondering how much you're burning? My high hour 502 burns a quart about every 20 hours, running Merc 25/40 conventional.

I'm at 740 ish hours on mine and they use the same as when I got the boat with 230 hours. I hear they have low tension piston rings so that's why they use oil. Also the higher rpm you run them the more oil you will use. A quart every 10-20 hours depending on use is what I see with merc 25w-40

Zinc has nothing to do with oil consumption.

Zinc is an additive used for anti-wear and as an anti-oxidant.

Ken

You didn't say what you are using for oil, but going to a heavier viscosity will help slow consumption down.

Ken