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It is carbed
Sorry mate I presumed you were running Denso plugs as you listed NGK as the alternative. But yep I see what you mean. Your lucky to have a 'parts motor'
TRy 75-1 Its worth atry but 100-1 is recommended. If engine runs well at 50-1 the extra lubrication can not hurt it.
Get some more history on boat&engine. Possible old fuel onboard,new fuel mixed with old, Service records, Fuel lines are 14 years old,ethanol fuels
Thanks, it's says 200hp on the cover, but I can't check the cylinder heads until later in the week as different location.
I'm unsure how I would