I have a 1983 Evinrude 70hp on a pontoon. Just bought it and first time out. Motor starts and idles great. I put it in gear and no problems. I start to throttle up and it begins to accelerate but then bogs down and quits. Starts right up but I can get no power. This motor has no miss or idle problems but just won't run out. Any ideas? Carburetor? Ignition problem? Any help would be appreciated.