Hi there, Sorry to hear about your engine troubles.
I just wanted to say that the pulley in your photo that you are talking about on the very lower left side down in the bilge area is going to be your sea water pump pulley, (Impeller Housing)
But just so that you are aware, That pulley should be just pressed on, and there should be no nut holding that pulley on.
Here's a link so that it will help give you an ideal of what it looks like, And also so that you can see there is no nut there holding that pulley on.
See number 18 in the link below.
http://www.mercruiserparts.com/Show_Pic ... p+AssemblyIf you still have any warranty left with Mercruiser, Then you might want to try to get your boat into a Mercruiser dealer and have them take a look at it just to make sure everything is in working order.
To me if that pulley is sticking out that far, then you may have other problems going on, Like maybe a water pump bracket is installed wrong or maybe it broken, Something along those lines.
PS, If your not sure if you still have any warranty left with Mercruiser, Then you could either post or PM me your engine serial number, and I might be able to let you know if you have any warranty time left.
Either way, I wish you good luck with it all.
