76 johnson seahorse 4hp

I hope I can get some help here i have a 4hp johnson that is giving me issues, it will run rebuilt the carb completely all new inside, had lost spark on one of the coil so replaced them both and now it starts easy, however after running it for a bit sometimes its 2 minutes sometimes it can be 35 minutes it stalls out and wont start and even seems to lock up on me where i cant turn the crank, after a few minuets of it cooling down it seems to free up and it will start just fine again, yes the water pump is new and working just fine checked all that and it also seems to not want to get too full rpm, some one please give me some help here thanks.

Ill look into that a little closer then thanks

In addition to "fdgator's" on target advice...... An engine getting hot enough to seize up will cause the powerhead bolts to loosen. Check "all" of them, especially the head bolts.

All the bolts are tight on the powerhead and it is a intermittent problem with the cooling system at low speeds it will not pump and at higher speeds it will pump water but it does stop pumping sometimes