I have a J150 Ocean Runner (J150NXEUE) that suddenly started idling at 1300rpm. Nothing in the manual's troubleshooting guide covers this and I hope someone has experienced this before. The boat mechanic said it was probably the power pack, so I changed it. Same problem. I have checked the plugs and they look normal. I did find a loose hose and a cracked manual lever on the primer solenoid and changed them, but nothing else obvious. When I checked the timing in neutral, it showed about 8 degrees ATDC. Something that did happen prior to this was cruising at 3000rpm for about four minutes, the motor suddenly started shaking violently. I immediately backed off the throttle and it smoothed out at 2800rpm. I crawled back to the slip at 1100rpm and it's been idling at 1300 ever since. Any ideas?