I have a modded 35 heads cam carb exhaust on a 17 48 boat and with a new prop on it the motor will turn up to 4950 rpm at wot.. i wanna drop my rpms and get it around 4650 4700 wot.... i thought maybe with a load it would drop way down but still turns those rpms up. I believe now i have a 50 tooth and 38 top whatever a stock 35 setuo is i was thinking about a 47 bottom whats everyone running witg similar mods

I'd go 48 on bottom, & repitch prop if still need more.

Not trying to be a dick, but there are many posts about gearing and expected benefits of re-gearing. I would recommend using the search function and also using MB forum as they many threads on that topic too. May save you some time.

What camo said sounds right. Also
Pull your top cover and make sure you have a 38 top. I've seen several stock motors that didn't have normal stock gears