Don't paint the coupling face

Don't paint this surface on any transmission

What Chris sees on the bench

• Painted coupling surfaces that have to be cleaned up and shaved down. On one 71 series direct drive the coupling had been in salt water and rusted, so it got replaced instead.
• Grooves and slash marks on a coupling surface where someone had a misalignment problem, got a leak, and tried to cure it with a washer and a bunch of silicone.
• A transmission that came back with the output nut backed off and the case torn up inside. Chris's read: the only reason that nut backs off is misalignment. His best guess on this one was misalignment or a motor mount gone soft and spongy where it bolts to the hull, which gives the whole thing play it should never have.

What causes it

If you've heard 5 thousandths, that's the factory limit for a different check, the runout on the damper and adapter bore and face, not the coupling faces. Between the output coupling of a Velvet Drive, a ZF or any marine transmission and the propeller shaft coupling, that 3-thousandths gap has to be right or you will cause damage. Put a gap of paint on there and it's going to be misaligned, and you're going to burn up the transmission or burn up the stuffing box. A soft motor mount can throw off the same alignment just as easily as paint, so check the mounts too.

Silicone does the same kind of damage. On a direct drive you don't need silicone on the coupling surface. It'll give you a misalignment and wear out the bore. And a washer plus silicone won't cure a leak that was caused by misalignment in the first place. It doesn't work.

Chris tells owners to pay the yard to check the alignment every year: it can save you tens of thousands of dollars next to what a misalignment failure costs.

1017-008 AS71CR 1.91:1 VELVET DRIVE

Fix and prevention

Don't paint the coupling surface, and don't load it up with silicone or add a washer. If it's already been painted, it needs to be cleaned up and shaved down so it's in good shape, or replaced if it's too far gone. Check the alignment yearly, after a grounding or hard strike, and after every haul-out, and check that the motor mounts are still solid while you're at it.

When to call

If you see paint, sealant or a washer on the coupling faces of your transmission, give us a call before you run it. Call (804) 333-3677, Monday through Friday 9 to 3 Eastern, or email sales@halemarine.com.

Related reading: output nut backing off and coupling damage and Velvet Drive torque specs.