Lower unit seal that connects to exhaust

jsw102503

Cadet
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Feb 7, 2016
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22
I received an Evinrude 7.5 hp Fleetwin that was, "perfect". Haven't made it to the lake yet because it keeps breaking. First the pawl and now a lower unit seal.

​The test bucket had a thick layer of oil after only 10 minutes. I drained a milk like liquid from the lower unit. I built a pressure tester and it seems that the lower unit is leaking through the exhaust. Does that make sense? Does anybody have an idea of what gasket that might be?

Thanks in advance!

Justin
 

Vic.S

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May 4, 2004
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4,690
You don't give a year or model number. I assume we are talking about a mid 1950s motor??

Shift rod seal (O ring), driveshaft bearing housing seal or gearcase to bearing housing gasket ?????


Dont forget with these old engines running a very oily fuel mix you will see quite a bit of unburnt oil from the fuel when you run in a bucket.but it is not difficult to distinguish it from gear oil

The gearcase sealing is not as good as more modern engines so a little water ingress into the gearcase may be difficult to prevent
 
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F_R

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Jul 7, 2006
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28,195
Assuming it has a full gearshift (FNR), what Vic said. Shift rod seal, drive shaft seal, drive shaft bearing housing gasket...any of those are inside the exhaust housing.

In any case, the sludge in a bucket is just the way it is. It is the oil that you put in the gas. It goes through the engine to lubricate it, then out the exhaust, into the bucket. They've been doing that for over 100 years.
 

GA_Boater

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Welcome aboard, JSW.

What Vic said about the oil scum in the bucket from the unburned fuel mix.

With milky oil in the lower unit, water can get into the oil from bad shift shaft seals, lower water pump seals and prop shaft seals. Yours sounds like the prop shaft seal/seals.

Is the motor a through prop exhaust? If yes, that could be why you think it's exhaust related.
 

racerone

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Dec 28, 2013
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No such thing as an Evinrude 7.5 fleetwin with through hub exhaust.
 
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oldboat1

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Apr 3, 2002
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9,598
guess I would like to know how it was pressure tested. I usually pressure test with the l.u. in water, looking for bubbles. Air pressure is only maybe 8-10 pounds.

I can't quite believe l.u. oil could be easily identified coming anywhere out of the exhaust -- not sure how you would really tell. The carbon/water/2-cycle oil in the exhaust housing would pretty much disguise anything else, seems to me. Might be the prop seal -- think I would want to get clear about that, though, before going through the trouble of resealing. Water in the gear oil could be something as simple as a bad or missing crush washer at one of the plugs. (btw, a vacuum test is a good idea too. A Mityvac works well.)
 
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