Merc 400 prop seal replacement

[ol' blue]

Hey guys, I've got a 1960 merc 400 45hp. Been a great motor, recently i noticed the lower end puking out all of the lube near the prop shaft all over my driveway. I cannot get the gear case cover to come loose, i have the tool but what is happening is the holes on the gear case cover are becoming oblong and the tool is just popping out. I can find another gear case cover but any thoughts on how to get this thing apart?

 

[Chinewalker]

Should be able to find another cover. Part number 20865. I’ve found them on other sites. Sacrifice the one you have, save the gear housing. Clean up the housing threads and lightly grease the threads when reassembling.

 

[DeepCMark58A]

E-bay there are tools you can buy to take the old mercury lower units apart.

 

[DeepCMark58A]

The 400 is a darn good motor I have a 1960 well.

 

[ol' blue]

I can find another cover no problem, I have the removal tool but can't get this thing to budge. Any thoughts on how to "sacrifice" the one that's on there without damaging other components? I've thought about drilling out the holes to a larger size and trying to carefully cut it out in pieces with a dremel... Any tips or tricks on this?

 

[DeepCMark58A]

Impact wrench?

 

[Chinewalker]

Dremel with a reinforced cutting disc.

 

[Texasmark]

I have removed just the seal because I couldn't get the "big" old spanner nut off a 1965 engine. A Dremel would work to poke holes in the seal and make places where you could insert an L shaped device to pry it out, or once you break the horizontal part of the seal, you can go after the vertical part....the part that touches the bearing carrier assembly. Once you get behind it with a punch and kink it, it will come right out with a pair of long nosed pliers.

You will be dealing with 2 seals installed back to back, one blocks water from entering, the second keeps oil from exiting. The inner one is easier to get out as you have access to it's soft side and have something with which to grasp to pull out....after you kink that lip too.........as I recall....been awhile.

 

[jimmbo]

I think the 4 cylinder 400 uses only one seal on the propshaft,
Some heat applied to the case might permit the retainer nut to rotate. A Dremil as mentioned earlier, along with a cold chisel might work

 

[Texasmark]

I think the 4 cylinder 400 uses only one seal on the propshaft,
Some heat applied to the case might permit the retainer nut to rotate. A Dremil as mentioned earlier, along with a cold chisel might work

May be a single. I haven't been into a 40 but the concept makes a lot of sense and since they were smart enough to use the concept on the larger engines, why not on the smaller....dunno! Not the designer.

 

[ol' blue]

I think the 4 cylinder 400 uses only one seal on the propshaft,
Some heat applied to the case might permit the retainer nut to rotate. A Dremil as mentioned earlier, along with a cold chisel might work

Tried using heat and my dad and I beat on it a bit but the thing will not rotate. Ended up losing a small chunk of material out of the housing but nut wouldn't budge. I'll try the dremel route and see how it goes. Thanks for the tips guys.

 

[Texasmark]

Tried using heat and my dad and I beat on it a bit but the thing will not rotate. Ended up losing a small chunk of material out of the housing but nut wouldn't budge. I'll try the dremel route and see how it goes. Thanks for the tips guys.

When you get all done with your seal, get some Brake Parts Cleaner and clean up the place where the casting broke off and glue it back on with JB Weld.

 

[Sande Ace]

An old mechanic said to turn or tap a stuck nut or bolt (or cover plate) in the tighten direction because "that's the last direction it had turned." Then, try to loosen it.

It's never worked for me but I always try it.

 

[ol' blue]

Hey Guys,

I started working on this thing again, it's been a while... I was able to remove the gear housing cover in pieces. However now i cannot get the bearing carrier to budge which is where the seal is located. It's not threaded in as far as i can tell but it will not budge even with some channel locks on it and i don't wanna break anything as i've made it this far. I attached the exploded view for reference. Has anyone had experience tearing this thing down?

 

[racerone]

Is it a left hand thread ?----Is it marked with an arrow ---( On ---Off ) by any chance.

 

[Texasmark]

Is it a left hand thread ?----Is it marked with an arrow ---( On ---Off ) by any chance.

Good thought but my limited experience with mechanics and thread types is that LH are for fasteners that may come loose as a result of motion of the interface in the CCW direction. Bearing carrier to housing interface experiences no motion.

On being frozen, your carrier is probably frozen just as your spanner nut was frozen. Looking at a cross section, you have a cylinder (the housing) and the round carrier with 2 contact areas, one at either end which are aluminum to aluminum. The internal one is probably ok as it is in oil. The outer one contains an O ring which divides that contact area into the inner half, oil immersed, but the outer half is alum to alum exposed to the same environment as was the spanner nut.

I think I would see if you could put things back together where you are and apply your efforts to removing the seal itself. I have done it several times and it's manageable and the SS-Alum seal housing to carrier bearing housing is easier to break loose. Utube probably has videos on how to pick a seal out of a carrier from the outside.

 

[racerone]

Texas man-------Does the reverse gear on these not rotate CCW and that would loosen a right hand thread ??

 

[Texasmark]

Texas man-------Does the reverse gear on these not rotate CCW and that would loosen a right hand thread ??

The interface between the prop shaft and the bearing carrier is a ball bearing.