I've got a 1985 Merc. 150 that just recently began "stumbling" between 1500 and 2000 rpm. It feels as though she is fouling plugs in that rpm range but when I pulled the plugs, all six were very clean. It runs great up to 1500 and from 2000 to WOT. I normally run 89 octane w/ Merc. Quickleen carbon removing additive. I ran out recently and added approx. 30 gallons without it. Could that be causing the problem? I'm also considering replacing the plug wires as I belive they are still original? Do you all have any other suggestions?<br /><br />Thanks.<br /><br />Brian
