Own a 2003 Manitou pontoon with a four-stroke bigfoot with just over 100 hours.  Lately have a high pitched constant alarm going off at snail speed, with a motor shudder the minute I try to increase speed.  Water stream is strong and steady from motor.  New water pump, and oil just fine. Any ideas what's going on?  I am at a loss with the owners manual for any help.  Thank you!