40 hp mercury

[tdw2676]

my boat runs fine at full throttle and idles good,but if i try to go slow it starts shakingandthen cuts off.any ideaswhat it could be?

 

[galamb]

Old gas, spark plugs that need changing, clog developing in fuel system (carb, filter etc), air getting into the fuel line, fuel pump on the way out....

I would start with fresh gas and new NGK sparkplugs (don't cross ref to Champions etc) and take it from there..