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Home›Repair guides›Mercury Marine›Replacing and/or Adjusting Serpentine Belt Tension

Mercury Marine MCM 4.3L / MCM 4.3L EFI — Replacing and/or Adjusting Serpentine Belt Tension

Adjustments · Serpentine Drive Belt

For the Mercury Marine MCM 4.3L / MCM 4.3L EFI, from the Mercury Marine service manual.

Procedure

  1. Loosen 5/8 in. locking nut on adjustment stud.
  2. Turn adjustment stud and loosen belt.
  3. Remove drive belt.
  4. Install drive belt on pulleys.
  5. Use 5/16 in. socket and tighten adjusting stud until correct deflection obtained.

Tools required

Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.

Specs & values

  • Proper tension is 1/4 in. (6 mm) deflection with moderate thumb pressure; measure at longest distance between two pulleys

Source: Mercury Marine service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.

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