Please help 1975 mercury 200 20hp

[jimmbo]

What prop should i be looking for? Mine was a 2 blade. I don’t know what pitch it is. Should i look for a 2,3,or 4 blade prop? Looks like mine is a 8 or 9 spline (i’ll count when i get home) Just not sure what i need. Thanks

What are you using the motor on? On a very light boat, some of the 2 blades have let that little 20hp, clip along really good

 

[Thrawn5499]

Thanks. I think i am going to but the gearbox on ebay. The one i found in my state is about 4 hours away, and I can’t work out a time to meet the person. It has a prop, and the shift handle i need, along with a few other odds and ends you get from having a complete second unit. But I can’t make it work.

I will be using this on an 15’ inflatable raft with 2 adults, and a teenage and child. Not even planning on going fast, just got a good deal on this 20hp motor so i went with it.

 

[Thrawn5499]

I was thinking about trying to straighten my shaft, but am afraid banging on it can’t be good for the gearbox. Also heating would be a good way to damage the seals. I also figure i will never get it very straight especially without taking it out. Even then it os doubtful.

 

[jimmbo]

That shaft has a Serious Bend in it, even if it were possible to straighten it, the metal has been stretched and would likely start to crack on the rebend. I certainly would be replacing the Housing, for the reason I previously said.

 

[Thrawn5499]

Yeah, that’s what i figured, just thought i would through the idea out there. As soon as I don’t someone would say something like all you need is a shaft straightener…. Yes i know that is not really a thing….

 

[Thrawn5499]

What oil do i need for the gear box? I seems there are a few different weights and types. Can’t seem to find what mine needs thanks

 

[jimmbo]

Mercury makes a couple of gear oils, their cheaper one is more than adequate

 

[Chris1956]

Any marine gear oil for mechanical shift outboards is fine.

 

[Thrawn5499]

Awesome thanks for the help!

 

[Thrawn5499]

Anyone know the proper socket to take the gearbox off? It is a 9/16 on top. I am guessing the bottom is too, but my thinest wall socket is too thick to fit.

 

[jimmbo]

You will likely have to get a Socket with a thinner wall.
Maybe there is just a bunch of crud in there(Can't see in the pic, too dark and even Photoshop can't lighten it up) that is keeping the Socket from going in

 

[Thrawn5499]

You will likely have to get a Socket with a thinner wall.
Maybe there is just a bunch of crud in there(Can't see in the pic, too dark and even Photoshop can't lighten it up) that is keeping the Socket from going in

Good thought, but it definitely is just too big. Hard to see there but it won’t even start in the hole. I notice it doesn’t look like a normal nut. I’ll keep digging and see what i can find out about it

 

[Thrawn5499]

Here is what i found from a parts diagram

34933

NUT, DRIVE SHAFT HOUSING TO GEAR HOUSING (7/16\")​

 

[Thrawn5499]

Ended up being a 1/2 lock nut. I got it off, And the one one top, but still can’t get the gearbox off

 

[Chris1956]

Some Mercs have a bolt hidden under the zinc anode.

 

[racerone]

Is there a hidden bolt ?----You should have 3 fasteners on your work bench I believe.

 

[Thrawn5499]

There could be, i am only seeing 2 in the diagram for this year. I also can’t find the 3rd one. Any idea where to look?

 

[Thrawn5499]

I think i found it. On the diagram at least. I have been looking at it on my phone. I pulled it up on my giant monitor at work. Looks like item 6 i have not taken off. Says it is a nut.

 

[Thrawn5499]

I got it off, there was a hidden nut. Thanks for the help. I’ll keep updating my progress

 

[Thrawn5499]

I just got the new gearcase in yesterday. Changed the impeller today on lunch break. I noticed the one i got today had an oring on one of the shafts. The shaft is item 16 in the pic, the oring is item 17. The oring was falling apart, and mine didn’t even have one on it. Oring part number is 25-38933.

Does anyone know what size oring will work? I don’t want to wait a week to get the correct one in.

Thanks