don't know for sure...I bought the boat knowing it had a water problem, and purchased it pretty cheap. Would a cracked block cause it not to perform well? Anyways, got the heads removed and pressure tested...they were good and noticed that back cylinder on both gaskets were blown pretty bad. With that and intake not very tight, I am hoping that was my problem. Hoping to have it all back together this weekend to back into the water. Boat ran around 75 mph on gps when done a short test run. Didn't give it all it had either.