2011 Optimax 150 snapped driveshaft

[the_dude]

Coming back from fishing with my kids and going about 30-35 the boat all of a sudden went into neutral. The binnacle was stuck and I couldn't shift forward or reverse (we got towed in). I thought the cable might be stuck or maybe it had broken, but after taking everything apart and dropping the lower I was rather surprised to see that the drive shaft had snapped. What is involved in replacing the drive shaft? I drained the oil to see if there was any metal in it, and there doesn't seem to be, so I'm guessing the gears are OK. The top vent screw to drain the oil is stuck and I can't get it open. Should I just pick up a used lower? Should I replace the drive shaft? What would cause it to snap like that? It's a fairly stout piece of steel. Is there anything else I should check for damage? Thanks.

 

[Chris1956]

A new gearcase from SEI will have a new driveshaft.

Does the end of the driveshaft look to be defectively cast/forged? Not sure how a Merc driveshaft can snap that way, if gears are in good shape.

Johnson 90HP motors did tend to break driveshafts, for some reason.

 

[alldodge]

Manufactures defect maybe. Should not be any harder then a sterndrive. Main issue is having all the tools to do it I would think.

Agree, SEI would be the easy way
https://www.sterndrive.cc/Mercury-Mariner-Force-Outboard-Lower-Unit.html

 

[the_dude]

A new gearcase from SEI will have a new driveshaft.

Does the end of the driveshaft look to be defectively cast/forged? Not sure how a Merc driveshaft can snap that way, if gears are in good shape.

Johnson 90HP motors did tend to break driveshafts, for some reason.

Not sure about being defective. I had a sneaking suspicion the guys that installed it didn't know what they were doing, but I put like 50 hours in it so it might have been installed ok. I'll look into SEI. $1k doesn't sound horrible.

 

[the_dude]

Any idea what would cause it to snap?

 

[racerone]

Where did it snap.------If the exhaust housing is bent then the shaft would flex and fail from fatigue.----Does the break look like it was sliced with a sharp knife or is it jagged ?

 

[the_dude]

Sharp knife break at the lower. I'm gonna order the SEI lower just want to make sure it doesn't happen again. Kinda scary with the distances i go in this boat.