VP used to use exhaust flappers/water shutters in the exhaust system just downstream of where the cooling water mixes in with the exhaust gases. For some reason they stopped about 20 years ago. They were there to prevent water from coming up into the exhaust when the boat decelerates rapidly.
I would guess that your engine is a bit too low relative to the water line of the boat and water can make its way up too easily. Risers between the manifolds and elbows were a common fix for this, but some new exhaust designs don't allow for this because the manifolds and risers are one piece. I'm not sure what can be done for your boat, but you should never ever pull the throttle lever to idle while on plane, always slow down gradually unless there's an emergency.
Your starter (likely a Delco PG260M) has a planetary reduction gear set with a plastic ring gear that will fail if the engine is hydro-locked. You can usually just replace the $10 gear
https://www.walmart.com/ip/New-Gear-Stationary-for-Delco-PG260M-Series-PMGR-Starters/824445923?wmlspartner=wlpa&selectedSellerId=101001368&&adid=22222222227257783475&wl0=&wl1=g&wl2=c&wl3=307316312058&wl4=aud-1308652556816
la-551611137986&wl5=9002460&wl6=&wl7=&wl8=&wl9=pla&wl10=127117920&wl11=online&wl12=824445923&veh=sem&gclid=CjwKCAjwx8iIBhBwEiwA2quaq4hRxy-Yb_YhWfZfFOVmzNYOe-RPf3DyQXYLHmkTfiFvZ6HaymQrsxoCueoQAvD_BwE&gclsrc=aw.ds to fix the starter.