Mercruiser Performance engine HP425, 1992 Gen V 454 block with a small B&M 174 blower.

Problem is that I have shred an 10 rib belt.

Checking the run out on the drive pulley indicates about 0.125inch misalignment and running you can see that the belt struggles to hang in on the pulley and I think its working hardwhich stresses the ribs - the tensioner on the blower is the pulley on the spring as in the attached photo.

Any info on what to look for or set up guides appreciated.

space the pully out

The run out is radial and axialy it aligns with the blower and the idler. I cant see what centralises the blower wheel on the crankshaft and as it is held by four bolts that go through the spacer I intend to tap it with a mallet to better centralise it - is that the right thing to do?

Take the drive pulley off and look at it. The holes could be wobbled out or it is not the correct pulley "made to work".

I have had to space the crank pulley out to get the right alignment before...Rob