Throwing Serpentine Belts

Discussion in 'General Maintenance/Repair Questions' started by capecodcruiser, Jul 16, 2019.

  1. capecodcruiser

    capecodcruiser Member

    450
    Aug 1, 2008
    Falmouth, MA
    2001 310, 350 HO's/Vdrives.
    Mercruiser MPI 350 HO's
    Hello All, recommissioning my 01 310 with 350 Horizon/Vdrives, after 4 years of inactivity. Have motors started, but struggling with keeping the serpentine on both motors! The pulleys did have rust and I have tried to clean them as much as possible while attached to motor. All turning parts are turning freely. Have checked alignment from raw water pump to crank pulley. That was off a little on one motor. Removed pump. Cleaned all mounting holes and that is better, but belt still wants to climb off of the rw pump pulley. Pulleys are perfectly aligned now. The other motor throws it almost instantly. I thought serpentines were a little more able to compensate for slight misalignment. Any thoughts would be appreciated.
     
  2. KevinC

    KevinC Well-Known Member

    Feb 25, 2011
    Long Island, NY
    2004 340 Sundancer
    Twin 8.1 V-drives
    Maybe do a double check the belt routing.

    -Kevin
     
  3. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    There was a service bulletin around that year that mentioned the alternator being out of alignment.
     
  4. capecodcruiser

    capecodcruiser Member

    450
    Aug 1, 2008
    Falmouth, MA
    2001 310, 350 HO's/Vdrives.
    Mercruiser MPI 350 HO's
    Thanks for the replies. I did find that and checked it today. The odd thing about this is that I have had the boat for a few years and ran it for 4 years before laying it up and I have never had an issue before. So, obviously looking at the rust on pulleys, etc. But that being said, the alternator on one motor was way out of alignment and I adjusted that. The RW pump was way off on the other one, fixed that. But, it had run that way for a few years. There is some common denominator that I haven't found yet. The belt on both motors is trying to come off the the RW pump. Half of it literally rides off.
     
  5. Snapon24

    Snapon24 Member

    65
    Sep 16, 2018
    Long Island, NY
    1988 340 Express Cruiser
    Twin FWC 7.4L Mercruisers w/straight drives
    I've seen a worn out belt tensioner make the belts ride off. Check if it has play where it pivots. Also if its a flat pulley on the tensioner, check to see if the belt is riding in the middle or towards the edge.
     
    capecodcruiser and PlayDate like this.
  6. capecodcruiser

    capecodcruiser Member

    450
    Aug 1, 2008
    Falmouth, MA
    2001 310, 350 HO's/Vdrives.
    Mercruiser MPI 350 HO's
    So, continue to chase this issue. What I have deduced is that while rotating the engine in correct direction, the belt goes from the stationary idler, down to alternator, to circulator pump pulley than down to crankshaft pulley. As it goes from alternator to the circ pump, it starts to climb off of that pulley, and subsequently the crank pulley. It appears my alternator pulley is out significantly from the crank pulley. I have removed it twice to check everything. All seems ok other than alignment. I will try to post pics of the measurement. If there was a way to get the alternator moved rearward, I think the issue would be solved. The crazy thing is that this boat ran this way for a few years. I don't understand what has changed by letting it sit. I am stumped and just stewing on it for a while to come up with a solution or reason. Any help gladly accepted! 66846106_10157590015185513_5931741850326007808_n.jpg 66896147_10157590114400513_158676261080662016_n.jpg 67310478_10157590151300513_6464965823990595584_n.jpg 67627036_10157590017355513_1383658860123783168_n.jpg 66846106_10157590015185513_5931741850326007808_n.jpg 66846106_10157590015185513_5931741850326007808_n.jpg
     
  7. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    Said there was a merc service bulletin on the alternator. I trimmed mine back and added shims to make up the distance I removed.
    Everything has to align with the crank pulley. With a 2' straight edge across the full diameter of the crank pulley you can rotate it around to the other grooved pulleys to check there positions.

    That's some rusty crap your working with, and that sure doesn't help. Belt eater
     
  8. capecodcruiser

    capecodcruiser Member

    450
    Aug 1, 2008
    Falmouth, MA
    2001 310, 350 HO's/Vdrives.
    Mercruiser MPI 350 HO's
    Fully aware of the rust and taking care of that as I go. Here is the service bulletin. My pulley is a good 1/2" out from the crank pulley.
     

    Attached Files:

  9. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    Looking at your pics, your alternator pully needs to be replaced not just cleaned up. notice how some of the pully ridges are as sharp as a knife. The belt is total junk and has to go, there 'res no ridges left on it. Your going to have to do whatever it takes to get your alternator back were it belongs. Maybe you can press the new pully on the shaft further.
     
    capecodcruiser and PMC like this.
  10. PMC

    PMC Well-Known Member

    Apr 10, 2009
    Long Island, NY
    2001 40 Sedan Bridge
    Cummins 6CTA
    I came here to say the same. No amount of wire brushing is bring that one back...... That alternator pulley has to be replaced
     
    capecodcruiser likes this.
  11. capecodcruiser

    capecodcruiser Member

    450
    Aug 1, 2008
    Falmouth, MA
    2001 310, 350 HO's/Vdrives.
    Mercruiser MPI 350 HO's
    Will do, thanks
     
  12. Espos4

    Espos4 Well-Known Member

    Jan 1, 2017
    Long Island NY
    2007 240 Sundeck
    350 MAG Bravo 3 W/DTS
    Agreed. It’s clearly the alternator pulley casing the chaos.

    The belt is falling off of the top part of the water pump and trying to be pulled back on by the crank pulley.
     
  13. Bt Doctur

    Bt Doctur Well-Known Member

    Aug 21, 2010
    New Jersey
    Ex SRV 240 Weekender twin
    in between
    I`d find out why the motor is so rusty, that idler bearing doesnt look that good either
     
    techmitch likes this.
  14. capecodcruiser

    capecodcruiser Member

    450
    Aug 1, 2008
    Falmouth, MA
    2001 310, 350 HO's/Vdrives.
    Mercruiser MPI 350 HO's
    The idler bearing is fine, have checked it. When I had to put the boat up, there had been some salt water flying around the engine room. Thought I had sprayed everything down with fresh after. Plus, here in the northeast, you would have to be in a perfectly controlled environment to stop rust. Let alone this poor thing has sat out for 4 years. Albeit covered, there is still lot's of moisture in the air and not always able to breath. Will work on the rust issues as I can.
     
  15. capecodcruiser

    capecodcruiser Member

    450
    Aug 1, 2008
    Falmouth, MA
    2001 310, 350 HO's/Vdrives.
    Mercruiser MPI 350 HO's
    Ordered a new pulley for the one alternator that was really bad.
    Worked on the other engine all day. The alternator is just so far out of whack with the crank pulley. I did find a roll pin/bushing on the front part of the alternator top mount and adjusted that which brought the alternator back some. But now when I start the motor, it just throws the belt right away. With a straight edge I am now parallel with the crank pulley at the top, but rotate the straight edge down, still on the alt. pulley, and at the bottom of crank pulley I am half inch out. I am almost out of options and ideas. Just decided to walk away for the day.
     
  16. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    That be your problem, they all need to be on the same plane, horizontal and vertical. Maybe your brackets are rusted and tweaked. Everything has to align with that crank pully. A level is helpful for the vertical measurment
     
    PMC likes this.
  17. bobeast

    bobeast Dance the Tide SILVER Sponsor

    Oct 22, 2017
    Isleton, CA
    2002 310DA
    350 MPI w/V-drives
    I was shredding belts on both motors. I performed the mercury bulletin work which involves adding a spacer between the alternator and the mounting bracket. Zero problems since. FWIW. If you only added shims to compensate for what you trimmed, you haven't really changed the geometry as called out in the bulletin.
     
  18. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    Not sure if your talking to me but I'm not the guy with the problem. Trimming and shimming works
     
    capecodcruiser likes this.
  19. capecodcruiser

    capecodcruiser Member

    450
    Aug 1, 2008
    Falmouth, MA
    2001 310, 350 HO's/Vdrives.
    Mercruiser MPI 350 HO's
    Pretty sure it was directed at me. Working on the trim/shim scenario
     
  20. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    Best of luck, brother
     

Share This Page

Show Sidebar