Hey guys, I just bought a Super 5 (model WH6 Ser.845160) and while on the river testing it out found that once I got it wide open it would quit running/stall/run out of gas after about 10 seconds. After backing down the throttle and giving the fuel line a pump or 2 I can refire the motor easily. Any suggestions on where to start?
It sounds like either a carburetor or fuel pump issue. Has the carburetor been cleaned/rebuilt. There could be fuel varnish built-up in it restricting flow, which would affect WOT running. Also, the fuel pump could be slightly blocked or could need the internals replaced.
Anyway, seems like the two places to start looking. You can get carb and fuel rebuild kits through oldmercs.com (go to the 1955 Mark 6 parts...they are the same as the Super 5). Before you spend the money, you might want to give both a cleaning and check the fuel lines. The rubber line which comes off the carburetor bowl to the pump could be in bad shape too....ethanol gas will eat away at the rubber over time. The copper lines are likely fine, but you could spray that out with carb cleaner, too, to be safe.