1986 johnson goes flat out with 2 fingers over air intake

by jon
(victoria australia)

i have a 1986 johnson 30elcdm ran great took it for an oil change sevice. marine technician ran a carby kit thru it tightened and replaced fuel lines, primer bulb,

compression test 160 159. picked the boat up all excited for a days fishing put her in the water ran like crap.
starts o.k idles, trolls o.k wide open feels like towing 44 gallon drum of cement. mechanic pretty well washed his hands of it. ran no probs before he got it. please help could it be electric primer system, carby,high speed jet, electrical, its doing my head in i love my boat