Water pump housing O-ring for 1958 Mark 10

[03aspina]

Doing the infamous impeller replacement on a ’58 Mark 10.  Yep, the one that takes about 50 times longer than the same job on a 10 hp OMC of the same year.  I’ve pulled the bearing, water pump housing, liner, impeller, and washer out of the tower housing.   The impeller housing has an O-ring that goes around its outer circumference.  Does anyone know where I can get one of these O-rings, or what the dimensions are for a modern equivalent?   Might also consider replacing the driveshaft seal that’s pressed into the end of the housing if one is available.   Looking forward to getting the motor on the water.  Powerhead is healthy with low hours and was test run for about 5 seconds.  Nice clean original; badge on the front is immaculate.  I think it’s the original impeller.  Got it from the original owner and from what I can tell, it was frozen in time maybe around 1970.  It still had the period-correct Quicksilver Aeromarine grease in it.

Thanks guys.

[labrador-guy]

Hello and welcome!  I have one of those Mark 10’s also.  The water pump is a real problem for sure.  Elmer K’s parts list are barely readable and in my opinion not much help.  I would suggest checking the hardware stores and maybe harbor freight for an O ring.  Hope you found an impeller.  Someone on here will probably chime in for one of those.  I found an impeller that I had to file the key way a little and if my memory serves me correctly I had to ream it out a little.  These motors run good and remember to be gentle when you shift it.

dale

[03aspina]

I actually already have the impeller, the same one you do.  It’s from a Mark 28 and it works if you file the keyway from what I’m told.  It actually fits pretty good just jammed over the square key, but I don’t know if it would tend to wallow itself out and eventually spin.  Going to fiddle with it a bit with some keys that we have in our stockpile and maybe custom file a key to fit instead of the other way around.

[dave-bernard]

mark 25 etc had the same impeller but the keyway was round. that is the one to file. make sure the impeller is loose on the shaft, or it will not center and burn. make sure the water is above the lower Dyna Float to cover the pump..

[03aspina]

Hey guys, a couple of other questions:

I’ve seen a video of this job on YouTube, and they put a gasket with RTV sealer between the midsection and lower unit.  This motor I’m working on did not have a gasket and no indication there ever was one (I am sure it has not been apart).   It would seem to me that the cavity with the gears and water pump housing would be sealed off with the o-rings and then with the gasket that is under the inspection plate up above.

Should any kind of sealant be used around the o-rings, like you do on the spaghetti seal on a two-piece OMC lower unit?

Is it advisable to use modern 90 wt hypoid oil in these, or should I stick with a 600 wt type of oil like the old Quicksilver Aeromarine was?

Thanks.

[dave-bernard]

Use John Deer Corn Head Grease. not oil…. no gasket.  just grease lube on the o-ring.

[Matthew Pieklik]

Does the Mark 28 take corn head grease also?

[dave-bernard]

Yes all auto tranny’s do. No oil.

[03aspina]

Thanks, I have corn grease.  Used it in the old motors from the ’20s and ’30s and it seems to get a little too runny compared to Lubriplate 105.  But that would probably make it perfect for this then as you suggest.

[03aspina]

One other question on this one guys.  Is there any trick to making sure the dogs are lined up when you slide the transmission in?  I can’t quite wrap my head around how the trans actually works.  Does the entire torsion spring rotate?  Seems that one spring is involved with reverse, and the other with forward?  I slid it in and the dogs seem to engage when I move the shift mechanism by hand and rotate the prop.  Thanks.

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