302 max RPM break-in

Break in has a couple parts to it. First, no matter what you do, avoid any high temperature. A new engine makes more heat so be careful always on that front. The boat is raw water cooled so this should not be an issue but do pay attention to heat.
The first start is most important for camshaft break in. If you want advice on this procedure just ask. Don't run the boat without breaking in the cam. 20 minutes minimum at 2,000-2,400 RPM and you will have this done for the life of the engine.
After this process most of your parts are proven to work, oil pressure is good, no oil or water leaks you can run the boat. A boat is the perfect platform for breaking in piston rings.   Accelerate from idle to 4,000 RPM at 3/4 throttle a couple times and your rings will be seated for life. Done. For the next hour engine time run it, vary the RPM many times in this hour, enjoy it. Most engine builders advise not staying at one RPM for any length of time on a new engine. After this one hour break in go use it any way you wish but again, watch the temperature and oil pressure close. If there is any issues they should show up in this time frame. It is always a good idea to change out the break in oil early. In a car they say 1,000 miles. In a boat, I really don't know but maybe 15 hours?