Might this work as a backup?

[jlsmith1000]

Hold all thoughts a wee minute perhaps.
Hope you don’t mind me interrupting things…but the prop geek in me has alarm bells ringing here.
If we are thinking that the prop is a 15” pitch…on a Yamaha 200hp, fitted to a 20ft boat doing 50mph…there is absolutely and certainly one or more of the details, definitely not correct. That engine would be screaming through the roof and/or limiting at the very least at or way before that kind of speed.
Excuse the ignorance of me…but what is a deck boat in particular? I’m a uk guy. Just so I’m clear. Is that like an open sports boat. Not a pontoon presumably?
Either way. Easiest to assume, is perhaps that your prop isn’t as low as a 15” pitch. Quite sure (but without checking) that there is no way a 15” prop is getting you to 50 mph or anywhere close, without limiting or blowing things through the side of the crankcase

Yamaha F200XB, 20.6" Boat. 14.5 x 15 prop as stamped (stainless). After testing this weekend, top speed at WoT and trimmed was ~45 mph at ~5900 RPM. Compared to a 22' result with same prop, same motor on Hurricanes website, I should be closer to 48 mph. Since there's a rev limiter on the motor, I'm going to try again this weekend and I'll won't be worried if I hit or slightly push past 6k RPM, the published max at WoT