Close to statistical study on OMC RDS Gear Cases

[raglover]

I have three "running" 35 hp RDS super quiet motors and one donor.

My first is a 1958 RDS super seahorse 35. It suffered from the crack under their water pump and is a loss

The second is a 1958 Evinrude Lark 35. It suffered from a bent upper lower unit that caused driveshaft bind

The third is a recently acquired near mint 1958 RDS super sea horse 35. (I wanted twins and paid too much). It has the same crack as my first….at least in the oil containing portion and will not hold pressure. It has not cracked under the pump, yet.

The donor is a rough as a cob 1959 Evinrude Lark 35 with the fiberglass hood.

All of the 58’s have had a structural problems in the gear case. I have looked at the 1959 version and found it to be sound.

There is a difference in the 1958 and 1959 cases in the shape of the anti cavitation plate. The 58 has a squared off plate. The 59 has the rounded plate like other big twin motors. It had to be a differed casting mold/die. I am deducing in my shop at least that the 58 is weaker than the later versions.

To be fair I have not run many 59 and laters so my data is one sided but I have lots of other standard big twins and have never found such a consistent issue.

Just passing my findings along, if you pick up a 58 super quiet pull the intake plate on the gear case and take a good look.

[chris-p]

Well, to be honest, no gearcase can withstand the pressure that ice creates when it expands while freezing.

The real issue, is owner/operator error and laziness.

Ensure that gearcase is totally drained before winter, and those drains are free and clear.

They are very often restricted and plugged. I have to drill many of them out to clear the path. Even had to remove owner installed plugging devices! Guys don’t like seeing their gearcases draining nasty sludge, but that is very normal, and protects them from the damage you describe.

[vintin]

quote Chris_P:

They are very often restricted and plugged. I have to drill many of them out to clear the path. Even had to remove owner installed plugging devices! Guys don’t like seeing their gearcases draining nasty sludge, but that is very normal, and protects them from the damage you describe.

Since the crankcase drain recovery system was installed on my 57 35hp the bottom drain drains so clear that I think it has become plugged and is not draining.

So every once in a while I take a piece of thick weed eater string and push it up the hole using vice grips. It helps to pre bend the tip of the line some. I push about ten inches of line up inside from the bottom. When I first got this motor about 3 years ago it was plugged so hard it took a small diameter metal rod with it’s end shaped like a flat blade screwdriver to open it up.

Everyone ought to know about these drain holes but many do not.

[raglover]

I agree with the clear drain issue. However, these cases crack in areas not affected by freezing water and from what I have read had a weakness for bending/bending easier after a strike than others.

Good news is it rarely freezes down here! That is a great tip on the weed eater sting, I have to try it!

Thanks

[jeff-register]

Raglover,
Seems to me anyone who has any time working on outboards have found many weird patches on them in some of the oddest places.
Example: bought a builder for usable reverse gear. Well, reverse gear was missing & forward was welded to the prop shaft. Yes it shifted the linkage but that was all. Damn, got burned again! E bay said it shifted too. 😮

[raglover]

Hana. I am sorry to her that Jeff. Btw, check your pm’s. So I have to eat some crow. Got the first crack sealed, found the driveshaft seal to be the next leak at 10 psi. Replaced that found the shift shaft seal to be the Next at 10 psi. Split the case and did all seals. Waited 6 hours and pressure tested to 10 psi and foud a crack in the lower half skeg, best guess from freezing!

Can’t win for losing on this one

[Author]

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