As a former dealer and small engine repairman, the advice given above particualy about the impellers is a must. If you are not able to, I suggest you get a Suzuki repairman to do that as there are tricks getting the splines to realign when you pot the lower housing back if that is the case with that engine.
Also, buy straight gas without ethanol but if not, do add the additive to help combat that issue and let the gas run out of the carburetor each time. If using in salt and brackish water, flush out the engine with fresh water on a regular basis.
dave condon