1989 90 hp wot

[ski332]

My 1989 90 hp Mariner starts good but when I open it up all I get is 3000 rpm I will run it on the lake for around 5 minutes turn it off and let it sit for 5 minutes restart and open her up it runs great I get 4500 to 5000 rpm then This happened last season at the end and again this season