1983 Evinrude 15hp loses power.

[scruffy63]

I have a 1983 Evinrude 15hp that has new mag., sensor coil, new power pack , new plugs. Starts and runs great powers up to speed great. But when I run it wide open for a minute or 2 it loses power and shuts down. Pumps good water according to pee stream, but seems to be hot. After cooling down it starts and runs good until wide open for a minute or so then dies. any advice? has a god looking impeller. Would plugged thermostat cause it.i