Hello all, have a question. In my 26 ft cruiser the i/o engine (Mercruiser) acting strange. Sometimes I can't reach speed of more than 10-14 MPH having RPM of not more than 3500 and it doesn't go any higher with gas trottle up to the max. In other occasions, I have no problems at all to have 33 MPH with 4500-4700 RPM.... Anybody have any idea where to look to fix that issue?