mercruiser lower unit


Old 08-05-08, 07:24 AM
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Join Date: Jul 2008
Posts: 12
mercruiser lower unit

last time I had the boat out i noticed drive line oil coming from the water intake on my Alpha I Gen II outdrive. My buddy said oh its just 4 bolts and replacing a seal.well it was 6 bolts and I cannot see where the leak came from , though it is apparentthat oil was leaking ( large amount ) and water was getting into the oil ( small amount )I have a new impeller that will go on ( even though the old one looks great cheap insurance) any been there done that advice?? oh yeah plz keep it simple cause my wife will be more than happy to tell ya that I am not a mechanic.... rc
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Old 08-05-08, 05:45 PM
Join Date: Jul 2008
Location: Montgomery MN
Posts: 541
I take it you already have the drive off. You're right about the impeller it should be replaced every 2 years even if they look good, it's just preventive maintanance. An overheated engine can take out head gaskets, melt wirers and exhaust bellows. Anyway back to the leak. If you have the drive apart look at the o'ring between the upper and lower it should be orange about the size of a pencle shaft. If you get a mercruser impeller kit it comes with the kit. Next step is reinstalling the 2 halves. Once they are installed the best way to test for leaks is to pressure test the unit by puting NEW gaskets on the lower drain plug and try to find a way to pressurixe from the top. I have a special tool for this but a mityvac or simalar will work. If anyone has other sugestions it would be great. The unit should hold 10 psi for a minimum of 10 min. Most of the time it will be a drain plug or vent gasket and will be easy to change. Next most comon will be a propshaft seal. This will have to be done at a service shop as special tools are required. Good luck

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