Johnson Super Seahorse 35 Lower Questions

[raglover]

My beloved RDS 20 is showing her age.

Found a hairline crack in the gear case on the forward side of the gear case cooling slot. I know these units are weak, become bent etc. is this a common failure point? I marine texed and looks like it is fixed but…..

I also cheanged the drive shaft seal and found the "wall" of the seal hosing is cracked too! Now a new leak point and a harder fix. I am going to marine Tex the OD but am concerned about the wall flexing and failing. I will put 847 around the seal too..likely success?

Now tecnical questions

Can I use a standard RD drive shaft with the round impeller drive key in place of the RDS driveshaft with the woodruff key? Will the round pin be able to drive the larger impeller?

Finally, what is the correct orientation for the drive shaft seal? Spring on lip facing power head or gears? Single seal, not double out of the standard reseal kit. Has the metal humped cover on one side.

Thanks as always, posting a classified for new gear case just in case

Allen

[chris-p]

Lip towards the oil, covered side up towards powerhead.

Curious, why do you want to swap drive shafts?

Can you post pics of damage?

[jerry-ahrens]

Marine Tex is really good stuff, so I’d give it a shot on the cracked seal bore.

[frankr]

You mean cracked like this? Common enough that I’ve seen a few. Sure makes for a hard to diagnose pump problem if you aren’t aware of the possibility.

image hosting above 5 mb

[raglover]

I will try to post pic today of damage and drive shaft. Frank, my damage is in the metal just above the front screw hole. It runs in board. Thankfully not in pump area….yet. Found it during pressure check b/c I found water in an otherwise sealed case.

Pics coming soon

[raglover]

Correction. After looking at Frank’s picture I checked mine again and it is cracked just like the picture. This thing is quickly approaching terminal.

I have to ask, can you marine tex this crack too? I have to think the cracks will just keep propagating.

So interchange wise, will a 1961 40 fit? Splines on top of drive shaft "looks" the same, but what about pinion? (In the event I find a short shaft donor and have to use my long drive shaft)

[wedgie]

quote FrankR:

You mean cracked like this? Common enough that I’ve seen a few. Sure makes for a hard to diagnose pump problem if you aren’t aware of the possibility.

image hosting above 5 mb

Now this is really good info. Might not think to look in there 😕 .

[frankr]

quote Raglover:

Correction. After looking at Frank’s picture I checked mine again and it is cracked just like the picture. This thing is quickly approaching terminal.

I have to ask, can you marine tex this crack too? I have to think the cracks will just keep propagating.

So interchange wise, will a 1961 40 fit? Splines on top of drive shaft “looks” the same, but what about pinion? (In the event I find a short shaft donor and have to use my long drive shaft)

I haven’t personally tried to Marine-Tex one in that location. so can’t say on that. Since your ’58 is a "Super Quiet", yes a ’61 40hp should be a direct swap.

[fleetwin]

Seems like you are kind of fighting a losing battle here….I don’t think you will have much luck getting that housing to seal back up with marine tex/JBweld if it is cracked in the upper seal area. I’m sure someone here has a decent housing, you run the risk of damaging the internal parts if leaks persist….

[raglover]

Final update, fleetwin nailed it. Seal is too loose. It has been relegated to the parts pile as it has good gears.

I have put a donor on but it has one stripped water pump hole, does anyone know the proper helicoil for this?

I have had bad luck with this style lower unit. My lark 58 lark 35 case was bent causing drive shaft bind. Found a donor for that and got it sealed up, but it is now on the Johnson so I am still short one gear case and have two bad ones in the pile.

Thanks for all the help

Allen

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