I think I have finally figured out the problem with my 30 evinrude. Symptom - idles ok, runs fine to WOT initally but cuts in and out when warm. I had replace the entire ignition and fuel systems to no avail. Answer - 1989 & 90 30 thru 40 hp have a S.L.O.W. system ( speed limiting overheat warning). Cure - replace the defective tempature sensor and might as well do the thermostat while I'm there. I haven't done it yet but feel sure I've finally came up with the answer. Thanks to Hooty and Joe Reeves for the various advice. 