I think I have a cooling problem.I ran my '98 15HP merc for the first time since I bought it from a private owner.I ran it about seven or eight minutes and no water come out.Yet it didn't feel overly hot when I touched the heads.Now I'm afraid to run it.I'd like to change the thermostat and waterpump impellar.Is this a big job? I'm mechanically pretty handy but never worked on Outboard motors.Where is the thermostat?what doesit look like?<br /><br />Bill