I have a 1988 Sport-Craft 250 off shore, with an OMC 5.0L engine. In the manual it states that the full throttle operating range "RPM" should be between 4200 and 4600 RPM's My boat on a good day can only do between 3000 and 3200 RPM's. I put new plugs in recently, it doesn't sound like it is missing. Right now I have a 15 x 19 prop on and before that there was a 15 1/2 x 17 prop on it. Is this a normal running speed for this boat? Is there something wrong? I am running with 92 octane fuel.
