After 45 minutes or so. under load, at about 32MPH, in Sea Ray 240, engine suddenly wants to stall. Will still run at low RPM, at a speed barely over no-wake. Can not go above 1800 RPM or so without shaking up boat and crew. Here's what I have already done:<br />1. Installed new water seperator/filter, spark plugs, distributor cap and rotor. Pulled plugs to check for moisture after running in slip at idle, (wanted to and did stall,) and found at least 3 or 4 plugs black and wet after only a short time. Bought it used with low hours this season, now has just over 200 hours, had 96 on her when we got her.<br />2. Mechanics at my marina say that it COULD be one or more bad spark wires or "The Box," that they say is an amplifier for the ignition. It could also possibly be a bad sensor that is designed to cut back to 4 cylinders (I'm told,) in the event of a overheating condition. Am hoping to solve problem before she is hauled/winterized, which is scheduled for the next week to 10 days. Thanks much in advance.