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I'm surprised you think it's way underpowered. There are lots of Sunrunner 5L's on the the market as STD .
I am yet to get down there, but my Son claims, he had no spark coming out of coil... replaced that and still no luck.
I have not yet been
If it has separate trim it a pre 1986. Pull the carbs and soak and clean, use new gasket kits and needles,replace all fuel hoses,replace fuel pump diaphragm,float
Sounds like your engine is running cold. Check the t-stat and make sure it is not stuck open.
Cold engine puts gas in the crank case
If the engine does not see minimum cranking RPM it will not start.