1998 Isuzu Rodeo Question Over heating and no heat, with rou

I bought this 98 Rodeo, 5 speed, 4 cylinder. I was told that it is losing water, and that it might be a head gasket. I was also told from another person that it could be that or a cracked head. I decided to search my self, and what I found is this: it idles rough, but when driving it is fine, both upper and lower hoses get hot after awhile, there is no smoke from exhaust of any kind, there is no heat from the heater. I can hear the fluid boiling, but no leaks. The temp gauge goes all the way up, but when I hit a good pothole or bump, it jumps down to normal, then goes back up to the hot end. I am assuming it is not a gasket or cracked head, but a water pump instead. But not being a mechanic, I am not sure.