Hi Guys.....Go to a Stock Outboard APBA Powerboat Race. I believe the correct term for it is "ventilation". In most cases reduce the throttle VERY slowly to allow the prop to"catch" up to the boat. Incidentally, while this is going on, you are "overrevving"the engine beyond your imagination! If the above doesn' work, you need to INCREASE he propeller "loading" on the engine. I ran "D" Stock Hydro back in the 1960's and here's an experience I had. I put a portabe tachometer in the boat set up for 4 cylinder two-stroke engines with a maximum rpm capability of 32,000 RPM. Just as the prop reached max "ventilation", the prop maxxed out @ 32,000 RPM, and fortunately it was only a momentary thing. Here's another experience I had while I was the Service Manager of a fairly good sized Marina. We took delivery on at least three different occasions of NEW Inboard powered Ski Boats that I believe had chrysler small block engines in them. I dropped the first one in the water for a Test Run. (These are pleasure boat now as received from the factory.) The ventilation was so bad I had to increase the throttle in small increments (just as in racing), thank God I knew what to do, or each engine would have blown up! When the prop finally "got a Bite" off we went. Then It got really interesting, the engine was turning so many RPM that it encountered "valve float" like I had never seen before! The RPM's were increasing beyond "redline" with a constant backfining out the carb. I went back to the Marina went up (not one, but two prop sizes), (both Diameter AND pitch). Went for another "Test Ride", The boat got on plane immediately and picked up around 6 MPH on top end no more back firing, and running safely in the right RPM range. The moral of the story is if you can't get on plane by feathering the throttle, you ain't got the right prop!!!! In the mentioned scenario I simply used a larger Diameter Prop to get the blade area (load) I needed. Forgive me for contradicting some of you, but reducing the blade area compounds the problem. This comment is based on close to 50 years of both 2 and 4 stroke marine engine experience.....and lots of classroom time as well. The way to launch a model raceboat might mean getting your feet wet, but simply dropping the boat from a dock is not doing either the boat or engine a favor. Seeing Is believing! Because of excess rpm caused by insufficient blade area, air is trapped against the thrust or back side of the prop, that is what causes it. I hope what i have said is beneficial to some of you....and saves you from some of the aggravation that I experienced when I was younger.
