Another Merc 470 Issue Again!!!!!!

[CAPTKEV85]

I love the power of this motor but hate it just as much. fresh rebuild this year. put the boat in around april. three test runs, each time one coolant hoses popped then boat overheated. mind you this is a fresh rebuild. Posted a forum back then, couple of guys said possible defective head gasket, do to the sweeling in the hoses. any way i replaced the gasket and what im still getting is alot of pressure in the cooling system under full load full throttle. if i open the cap there is no visible air bubbles coming out of the antifreeze. so i replace the cap thinking it was bad (not venting or something like that 11psi). i take the boat out for a run its steaming from the cap but not overheating. this was at a 3000 rpm run for an hour. each trip im losing a half a cup of antifreeze assuming its just pouring out of the cap. then a friend said to check the overflow hose for cloggs or kinks. there was a clogg at the beginning of the hoses. (now i think i found the problem... not) i cleared the hose. Now i go out for a test run again. put the boat full load 100% wot. antifreeze fills the plastic resivour bottle and then spitting out the top of it the entire time at wot, 5 minutes i would say, now the temp started to rise assuming i just pissed out antifreeze. come off of plane she cools down, the level in the res drops down, which its sucking the antifreeze back in. so tomorrow im going to see if theres anymore antifreeze in the res. if there is then the engine should be full of coolant and i will test run it again. this motor is driving me nuts it runs like a champ plugs are clean no milkey oil no oil in antifreeze, and no visible leaks accept the squirting out of the bottle. any ideas guys. please this would be much help to my problem.