HELP! What is this? Merc 4.3 (see pics)

[mercengine]

Hi there, My serpentine belt dropped to the floor and one of the round disks that it runs around fell off. I know it's bad, but I just had a bunch of repairs and I want to go in educated bc I just had a bunch of work done (gear box replaced). Here are pics (on left of a similar engine with the disk where it should be (circled in blue) and on the RIGHT is my engine where the disk fell off, and the pic of the disk that fell off.

 

[Eric 3.7LX Alpha 1]

Looks like your circulating water pump has bit the dust. Not bad of a job to replace, make sure you get a marine one, they're made differently than an auto one.

Check the belt over for any damage or cracks...

 

[alldodge]

I would say yours is like the one on the bottom left and you have the Delco alternator. Note the way the belt runs

 

[Bayou Dave]

Doesn't it just bolt back on with 4 bolts?

 

[Bt Doctur]

looks like it sheared the shaft and fell off with the 4 bolts in the plate

 

[Bayou Dave]

looks like it sheared the shaft and fell off with the 4 bolts in the plate

Yep.... I didn't notice that.

 

[mercengine]

Yes, it sheared off at the base/shaft.

 

[Bondo]

Ayuh,..... Welcome Aboard,.... Get, 'n install a new circulatin' water pump, then bolt yer old pulley back on,....

Ya oughta be back up, 'n runnin' in am hour or two,...