Lower Unit diagram

[Joe Kay]

Just found this forum yesterday and it looks like what I need.
I have a 1984 Mercury 90 hp 6 cylinder outboard and I need to get at the shift cam through the gear box. Before I start taking out the prop shaft and gears etc., I was wondering if there is a manual, diagrams, and/or instructions specifically for that engine. The manual I have is helpful but it covers a lot of motors of different years and horsepower and there are differences in some of the parts. If anyone can help me find the material I need, I would be very grateful.
The serial number of the motor is 6436732 (if that helps).
Thanks
Joe

 

[Drew220]

Looks like once your drop the lower unit the shift cam should be right on top and shoudn't require brain surgery on the lower unit to get to it. You should not have to remove the prop shaft or gears. just unbolt the lower unit. You may need special tools to remove the gears anyway

https://www.mercurymarine.com/en/us/.../parts-catalog

 

[Joe Kay]

Drew220

Thanks for your reply and especially for the link to the Mercury Parts Catalogue. It contained a diagram of the lower unit of my motor and will help a lot. However, I think we are talking about two different parts.
The part I was referring to is the shift cam which is located at the BOTTOM of the shift shaft, not the top. It is in the gear box at the end of the propeller shaft farthest from the propeller. A mechanic removed the lower unit to find and fix an oil leak. He told me that the shift shaft was not engaging the shift cam because the shift cam was probably damaged and as a result the gears could not be shifted. He estimated it would cost in the area of $1000 to replace the shift cam. I was not about to put that much money into so old a motor, especially since there are other issues with it. I took the boat home with the lower unit removed. My nephew wants to work on it. Now the shift cam may well be worn but I think it is also possible that the mechanic pulled the shift shaft out causing the shift cam to move, making it almost impossible to get the cam back on the shaft without going into the innermost parts of the gear box. Comments welcomed.
Thanks again for the link
Joe

 

[jimmbo]

Drew, you are referring to the reverse lock cam.