Have your propeller checked to be SURE it is straight. A bent prop can cause this.
Is the "beep" a beeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeep (continuous) or is it a series of individual beeps ie. beep, beep, beep, etc.
What doesn't add up is the boat has been a cold climate up north the last three years, so I don't think there is any algae. Also the glass fuel filters
Racerone, is there any chance of a spacer or flat thrust washer sliding out of place and or into the wrong place in the housing?
List price for a new one is a little over 1100 bucks. I would expect that it would be pricey even in the second hand market (minimally half the price