Just wondering, does the 70 model have actual reed valves or rotary valves? Last time i took the carbs off i could swear it had rotary valves. I am asking out of curiosity. But this motor runs off and on all day. I have literally done everything except a linc and sync procedure: carbs rebuilt, fuel pump rebuilt, cleaned fuel tank, replaced fuel hoses, replaced stator wires. Has good compression and spark, I checked when it was cold. The boat struggles to plane and will bog down, but once on plane it seems fine, sometimes it will power up to plane and others it wont, very unpredictable. It used to run great until last summer, not sure what happened. I guess a linc and sync is in order though. Any other ideas?