Have a 1971 Chrysler 45 HP outboard that runs GREAT at any throttle speed but at idle and no wake. When its in neutral at idlel or in the no wake gear it will occasionally severly BUMP or sometimes stall. With a little throttle its fine. Could it be a gas delivery issue? I took off the gas bowl and drained/cleaned it. Still same issue. Plugs look great! The gas line and squeeze ball are older, could it be a loosing prime isse? How would I test for that?