I was cruising down the lake yesterday with the wife and out of nowhere the motor loses almost all power. The motor would still run but not have any more power than idle. If you tried to do more than idle it would make a loud intermittent knocking sound. We were able to limp back to the ramp at idle speed and load back up. After some trouble shooting today I discovered that there was no spark on any of the port side spark plugs. Does anybody have any ideas what the problem may be or how to fix it ? Any insight is much appreciated.