have an 04 600 efi mc, lost 2 pistons last winter on the clutch side,both burned down on the exhaust side of the piston,it only seems to happen during wot,go up to 3/4 trottle the sled is the best kind but as soon as you go wot on a lake for a mile or so the piston melts on the exhaust side.any ideals on the problem?