Boat Maintenance: Prop seal replacement on Mercury outboard
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Name:
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CAT BOAT
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Subject:
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Prop seal replacement on Mercury outboard
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Date:
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4/23/2012 10:27:37 AM
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Indeed you can change them without removing the lower unit. First off, I assume you are leaking oil from the propshaft. Before you go take the lower bearing carrier out, make SURE that is where the leak is. You have to remove the lower carrier because it is indexed to house two seals. (Special tool or creativity required) They are identical in most cases and are installed back to back (facing away from each other) The reason for this "double" install is one keeps water out, and the other keeps oil in. Of course, replace them both. The reason I said make SURE that is where you are leaking is because more times than not, the upper bearing carrier seal directly under the water pump impeller houseing fails and oil escapes into the exhaust tower and runs down and out from around the prop area. A common reason for upper bearing seal failure is the lack of changing the impeller. Although it is still pumping water, Over time the impeller looses some of its effectiveness and cooling water becomes less available. The Impeller base becomes worn, and being that is sits directly on top of the bearing carrier the carrier becomes hot. Most think that the impeller is only to pump water to cool the engine. While this is its most important function, this is not its ONLY function. That is why Marine shops stress impeller replacement. (Many people have said "It's another way for the mechanic to make easy money") Simply not true. If you are not 100% sure that your lower seals are bad, simply remove the lower unit, drain the oil and then pressurize the unit to 15psi (special tool required) and see where the leak is. $550 sounds a little high, but if it has given you 7 years of good service you may as well go ahead and do it right. Sorry for the long post, but I feel this is a very important subject.
CAT
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