Re: 1998 200HP(EFI) Mariner help needed
Check compression as John suggested and check spark also. Here are some things to check that will cause smoking and bogging on that engine.
This engine does not have a bleed system like a carb engine. The EFI bleed system sends all the unburnt fuel back to VST tank to be recycled. This is controled by a shut off valve and filter. If the filter is stopped up it will cause engine to load up and hesitate.Also a bad engine temp sensor will make it run rich as ECU sees engine as cold. A overpressurized oil tank will also make engine run rich as it forces oil thru check valve into VST tank. A TPI will make it run rich but more toward top end than idle. A sticking fuel pressure regulator will cause problems as pressure will not be within spec's.