Help - Hit an underwater stump


Old 09-19-10, 07:17 AM
Thread Starter
Join Date: Sep 2010
Location: USA
Posts: 1
Help - Hit an underwater stump

We were riding at a good speed and hit an underground object (probably a tree). There was big thump at the back of the boat and the boat would only go forward at the lowest speed from that moment on. The engine revs but the boat won't move to a higher speed. Reverse works, neutral works and forward works but only at the lowest speed. we pulled it out of the water to discover the lower fin of the rudder below the propeller has been sheared off. We have a Mercruiser 4.3 L engine 2004. The propeller looks in good condition and turns normally when the engine is off and it is in neutral. Any thoughts of what the problem might be?
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Old 09-19-10, 03:24 PM
Join Date: Jul 2008
Location: Montgomery MN
Posts: 541
Welcome to the forum.

Pull the bottom drain plug from your lower unit, if there are metal chunks on it there is internal damage. That outdrive has a clutchdog, meaning a gear slides on the propshaft to engage forword and reverse and shouldn't slip.

Another thing to look at is if the prop hub has cracked or separated from the impact. Remove the prop and look for a cracked hub if it's a torque flow style, if it's a rubber hum look for balls of rubber that are about the size of rabbit droppings.

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