I would suggest that will be very bad for the motor to run it in like this. Running in engines should be done under normal (but not excessive) load, so that everything beds in properly. I know that running in a vehicle engine in this way would do it long term harm, and I can't imagine outboards are any different. I was once told that the rings etc would not bed in, bores would be glazed etc. Same with idling engines for long periods, especially when they are cold.
A Boat is a hole in the water, surrounded by fibreglass, into which you throw money...
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