Merc hp500 efi
#2
Registered
top end should be looked at around 250-275, the valve springs are what you need to check. But a complete rebuild is 500-700 hours. But all this depends on you maintance and how you run the boat.
#3
Registered
mine have 550 hrs. Recent compression check by Performance Marine Service of Lake George, NY didn't show any problems. John recommended "refreshing" the top end at 700 - 750 hrs. He estimated about $7000.00 for a pair of Merc Blue Motors, if you did it before you started having problems.