GOODT

look behind the mtr and check and see if you see rubber "dust"

cuda

When I lost a coupler, t here was no doubt. It was like going to neutral at 3500, then black smoke billowing out of the engine compartment. I had no idea what it was, I had Deb hold the fire extiguisher at ready before I opened the hatch. I had a two and a half idle back to the ramp, and it was rough that day.

I'd look for something else. I think the coupler would go all at once.

RaggedEdge

Have take out a bunch of them over the years and agree they seldom let go due to the rubber failing. Normal failure is that the splines wear and become very peaked or pointed, reducing the contact with the shaft to the point it just can't hold the power any more and lets go. You can easily check them by pulling the drive off and looking in at them. If what you see are splines that are pointed looking they are not long for this world. Based on rubber smell it does sound like your problem is elsewhere. Good Luck.

LAKESIDE RESTORATIONS

The splines usually twist out but some make dust or rubber boogers in the back.. Also make sure your shift cable isnt routed too close to the coupler that protrudes from the bell housing on its way into the transom plate. I have seen a rare few that rubbed there & made a stink & then cable/shift problem. The plastic got hot & melted through the windings & siezed the cable after it cooled. I have also seen this when an impeller fails & the customer runs the boat. The shift cable is against the y pipe in some & melts.. again rare but I have seen it a few times. It may be worth checking them.. Jamie