Mercury 40hp/30 jet ser 0C168157

[trynhooker]

Ok this one's got me stumped...
Customer of mine has this engine and it keeps getting stuck in FWD gear.
I can remove shift cable and reset linkage to F N R with the engine off. Then after a few shifts it goes back to FWD only?

The weird thing is even when it's stuck in FWD, I can disconnect the shift cable from the hold-down bracket, moved it to any position (F N R) and it won't shift into any other gear but stays in FWD.

Another weird thing is the engine has a shift coupler installed over shift shaft in lower unit, yet it does not show up on any drawings?
Like here;
https://www.mercruiserparts.com/Sho...543&bnbr=200&bdesc=GEAR+HOUSING+(DRIVE+SHAFT)

I purchased the GUIDE-SHIFT SHAFT (AN ASSEMBLY AIDE) like here;
https://www.mercruiserparts.com/Sho...=543&bnbr=130&bdesc=ADAPTOR+PLATE/SHIFT+SHAFT but that doesn't seem to be anything but an assembly aid..

Anyone got any ideas?

 

[fastjeff]

Sounds like the shifter in the LU is not going far enough CCW to put her into N or R.

Was the LU off recently? If so, it's off a spline. If not, the shifter shaft may be corroded and twisted.

Jeff

 

[galamb]

I see the "coupler" (shift shaft guide) in the service manual, but as you note it does not show up in any parts diagram and there is no part number listed for it anywhere.

However, it looks to simply be a guide tube to ensure the upper and lower shift shafts mate up during assembly.

Agree with Jeff and would suggest further that if the lower unit has not been "played with" that either the splines at the bottom of the shift shaft are shot or the shift cam itself is either damaged or stripped...

 

[trynhooker]

The coupler is a connection point between the 2 shift shafts and acts as a guide also. It is designed to fit over the lower shaft (has the cutout that matches the lower shift shaft) and the upper part of the coupler fits on the upper shift shaft. Without the coupler the 2 shafts cannot connect together.

I've had the LU off to verify the shift arm is installed correctly.

As I stated, you can set the shifter up correctly where you get F N R, but after you connect everything back and operate it a few times it goes back to F only.
The coupler on the unit is slightly damaged (a piece of one side is broken off) but it still connects correctly and shifts the unit.

Would have liked to replace the coupler but since it's not listed..that's not going to happen.

Has anyone used the assembly aid>? It doesn't get mentioned in the book and I don't know if that's supposed to remiain installed or what? Not even sure why this part is made if it doesn't belong in the LU. This isn't rocket science and this unit is easy to bolt on and line up.

Thanks for all the comments so far

 

[dennisa14]

I have this same engine, Mercury 40hp/30 jet, and I cannot get the lower unit off. All of my previous engines had a place to disconnect the shifter shaft, but I cannot find any where to disconnect the shift shaft on this motor (no screw coupler, not set screw, no cotter pin). Are the top and bottom shafts supposed to just automatically separtate at the coupler connection mentioned by trynhooker below? (If so I have a stuck shaft.)

Thanks for any guidance...

The coupler is a connection point between the 2 shift shafts and acts as a guide also. It is designed to fit over the lower shaft (has the cutout that matches the lower shift shaft) and the upper part of the coupler fits on the upper shift shaft. Without the coupler the 2 shafts cannot connect together.