1984 35hp Lower Unit Removal Trouble

[NJMerc]

Hello everyone,
I have a 1984 Mercury 35hp that I'm trying to do the impeller on. I can't figure out how to get the lower unit off. I think that it's an issue with the shift shaft. The manual says, "Remove the shift lever coupler located in the bottom cowling behind the carburetor."

The Serial number is 6530726.

Can someone shed some light on this? The manual has no pictures or diagrams of where this is.
I can get the lower unit to separate about a quarter of an inch and it moves easily in that range.

Thank you for any insight you can give!

 

[jimmbo]

You just have to remove the Bolts/Nuts that hold the Gearcase to the Exhaust Housing, and it will come apart. Don't forget about the Bolt hidden by the Trim Tab. The Upper shift Shaft stays with the Exhaust Housing, and the lower Shaft is part of the Gearcase, they are Splined in such a way, they will only line up one Way. Some People like to leave the Gearcase and the Control in Forward, others prefer Neutral.

 

[NJMerc]

Jimmbo, thanks for the reply, but I've removed the nuts and bolts you mention including the "hidden" one which really is not very much hidden. If I didn't remove all the bolts I would not have been able to separate the LU about 1/4" all the way around.

I've used the side bolts as leverage by inserting flat metal between the top of the acorn nuts and the exhaust housing and backing the nuts out. I've used a hammer and block of wood. I've slathered it up with PB blaster. Something is physically stopping it from separating. The only thing that I haven't done is whatever the manual is specifically referring to. It's specific to an outboard built in the 80's before 1987. It's referred to as the "older units" in the manual.

I included the pages from the manual so everyone can see what I'm referring to.

 

[Chris1956]

If you look under the lower carb you should see the top of the upper shift shaft. It should come up, if the shift shaft coupler is not seized. You may need to remove the shift cable to pull the upper shift shaft up to prove it is not the shift shaft coupler.

Sometimes the driveshaft rusts into the crankshaft end. The driveshaft on an '84 should be stainless steel, but they can still rust/corrode. If it turns out that the driveshaft is rusted into the crankshaft, it can be hard to separate.

Wood wedges can help. Hanging the motor upside down and spraying the driveshaft with penetrating oil can help. The penetrating oil can run down the driveshaft into the crankshaft coupler, maybe helping to free it up.

Other methods are avail but are destructive to the midsection or driveshaft.

 

[jimmbo]

What Service manual are you using?

 

[NJMerc]

If you look under the lower carb you should see the top of the upper shift shaft. It should come up, if the shift shaft coupler is not seized. You may need to remove the shift cable to pull the upper shift shaft up to prove it is not the shift shaft coupler.

Sometimes the driveshaft rusts into the crankshaft end. The driveshaft on an '84 should be stainless steel, but they can still rust/corrode. If it turns out that the driveshaft is rusted into the crankshaft, it can be hard to separate.

Wood wedges can help. Hanging the motor upside down and spraying the driveshaft with penetrating oil can help. The penetrating oil can run down the driveshaft into the crankshaft coupler, maybe helping to free it up.

Other methods are avail but are destructive to the midsection or driveshaft.

Thank you, I will attempt to remove the pin in the upper end of the shift shaft below the carb. It's a tight area, and I'm not sure how I'm gonna do it without taking more parts off. I stopped down at a local shop and they confirmed what you mentioned as well. I'm guessing that the impeller has never been replaced because the guys said that people don't put the original rolled pin back in, they put in a cotter pin or a hair-pin (R-clip) so it's easier on the next guy to pull out. I'm hoping that since I got about a 1/4" of play that the drive shaft isn't welded to the crank, but we'll see!
Wish me luck!

 

[NJMerc]

What Service manual are you using?

33478-1965-1989_Mercury_Mariner_Outboard_2hp-40hp_Workshop_Service_Manual.pdf

 

[jimmbo]

Is that a Mercury Manual, or some 3rd Party Manual?
That pic/section you showed in Post #3 looks like from a very low Hp Motor.

 

[NJMerc]

Is that a Mercury Manual, or some 3rd Party Manual?
That pic/section you showed in Post #3 looks like from a very low Hp Motor.

I believe it's an official manual. It covers 2hp to 40hp, so the engine you see falls in that range. It's about 500 pages. I think it's pretty accurate.

 

[racerone]

Doubt it is the shift shaft.-------Since it moved a 1/4" and would work it up and down 10/ 20 times to loosen it up.

 

[jimmbo]

Top Pic: Lower Shift Shaft #43 simply slides into
Lower Pic: Upper Shift Shaft #19

 

[Chris1956]

Gee, to be clear. You do not need to remove the pin on the upper shift shaft. I recommended you lift up on the upper shift shaft to verify the upper and lower shift shafts separate.

It is very likely that the issue is the driveshaft corroded into the crankshaft.