Shifting Trouble Mercruiser 165

[BigWeakSauce]

Good evening!!!! 1974 Mercruiser IL6 with pre alpha drive (MC1?).

Took my family out on the lake for the first time this afternoon and boy was it an experience! That said I had some trouble shifting gears (I already cant get reverse).

Interesting thing was up to 2000 rpm and 10mph or so it ran great, sounded great. Hit about 2500 rpm and slipped out of gear, fell into neutral, shifted back into N and got right back into F no problem. Then while waiting to dock at the ramp I couldnt return to N, the lever was in N but I was still idling about 600rpm. Then I got N and couldnt get back into F! Threw the lever in R and back toward F a few times and eventually got back into gear. I dont think my dog is worn out but who knows, when I engage forward its very clear, engine catches and boat starts forward, no audible slipping at all and feels like a clean shift. It feels to me more like the lever isnt forcing the shift action every time.

combined with slipping out of F at 2500+ rpm (only tried once, only happened once, newborn onboard)
what am I looking at as far as problems??

 

[BigWeakSauce]

Update... the high RPM issue was likely due to prop spinning, popping a new one on soon to confirm. When taking the prop off I noticed some play in the shaft if I pull it out, maybe 1/4 of wiggle in and out, seemingly enough to disengage the dog, should that shaft have any play?
still not sure about the shifting in and out of gear trouble...

 

[Rick Stephens]

Should not be play in the output propeller shaft. Sounds like something is worn out like a bearing shot or the housing worn out. Probably more expensive to fix than to look at installing an SEI brand aftermarket drive on the boat.

 

[BigWeakSauce]

Should not be play in the output propeller shaft. Sounds like something is worn out like a bearing shot or the housing worn out. Probably more expensive to fix than to look at installing an SEI brand aftermarket drive on the boat.

Good to know. Any thoughts on the shifting issue? I would think a bad shift cable would cause shift interrupt issues rather than not shifting at all. And I'm having trouble translating other posts, people say "hard shifting" but not sure if that means the throttle lever is physically hard to pull or if it's just difficult to achieve the shift.
My lever moves smooth, feels like it's in good shape. Just intermittently nothing would happen when I shifted it.

 

[Rick Stephens]

No idea since if you have a bunch of play in the propeller shaft that is where the shift gears are. That by itself is a wildcard that makes diagnosis a waste of time. Shouldn't go out and float that boat with a drive failing.

 

[BigWeakSauce]

Update here, lifted my drive to get a look at the shift cable and noticed lifting the drive actually changed my gear to the R position (still not locking the dog tho, must've missed a spline on the lower reconnect). Don't think the drive lifting should impact the cable at all. Lowered it back down and watched the shift boot turn back to F. Also when doing so I notice my shift cable at the aft end of the cable bellows was heavily corroded, the sheathing pealing away and the inner metal core was exposed. I'm having a new cable installed in a few days after seeing that and will have them reset the lower in the right spot! hopefully we'll be back in business soon!