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lower unit using/losing gear oil

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merrittislandjohn

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i purchased this sweet 2008 crownline 252EX w/6.2 and brava 3 drive about 10 months ago with only 22 hours on it. I serviced everything since it mostly sat and was a freshwater boat. motor oil change,new impeller, new batteries, added a fresh water flush sysytem etc..I use it in salt water but its on my lift when not in use. Now i have 45 hours on it and i started getting the audible alarm and figured out with the help of my mechanic...its losing gear oil. How much..not sure, this is the first time since I own it that its happened. I dont really see any visible signs of a leak. I ve read about pressure testing etc. with this low of hours any one have any idea what the most common problem might be?
 
When you changed the LU oil did you fill it from the bottom drain? Inspect the pass thru nipple on the gimble where the reservior hose attaches. Is there an oil slick in the bilge? You can lay a white rag under the gimble assy inside to see if there is a slow leak.
 
Guyjg
The gear oil was checked and looked pristine when i bought it so we never changed it. the previous owner had it done at the first 20 hour service. the bildge looks clean...and i rinse it out everytime i use the boat when i flush the manifolds. nothing dripping down the outside of the transom either...its apparently a very slow leak. i will try putting the rag under the gimbal and see what happens. thanks
 
Carefully inspect the cavitation plate where the LU and Upper half meet. There is a quad ring that seals the oil passage between the two halves. It may ahve been dislodged when the halves were reassembled and not sealing 100%. You could pressure test the outdrive but will need to drain the oil. Someone may have omitted the washer on the drain or vent or did not remove the old washer and installed another on it.
 
Fully agree with a Presssure/Vacuum leak down test.
The reservior line must be closed off or circumvented during this test.

Or.... if the drive gear lube is not water contaminated, fill the reservoir to the correct level, and operate it for a while, and see if the same loss occurs.

The reservoir supplies gear lube to the drive, and it will compensate for any heat/cold expansion/contraction.
This means that we may see a very slight loss and a return from/to the reservior.

If while the gear lube was being installed, and if not purged of all air, you may simply be seeing some compensation.

In a rather crude sense, this is somewhat similar to a car/truck cooling system whereby the expanding coolant is directed to the recovery system, and is then drawn back into the system as the coolant returns to ambient temperature.



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Last edited:
merrittislandjohn said:
i purchased this sweet 2008 crownline 252EX w/6.2 and brava 3 drive about 10 months ago with only 22 hours on it. I serviced everything since it mostly sat and was a freshwater boat. motor oil change,new impeller, new batteries, added a fresh water flush sysytem etc..I use it in salt water but its on my lift when not in use. Now i have 45 hours on it and i started getting the audible alarm and figured out with the help of my mechanic...its losing gear oil. How much..not sure, this is the first time since I own it that its happened. I dont really see any visible signs of a leak. I ve read about pressure testing etc. with this low of hours any one have any idea what the most common problem might be?
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Your problem description is a little vague. Some things to comment on: Loosing oil while running only? Static loss? Have you checked the Drive Oil for water intrusion? Pressure Testing is a MUST. On Bravo III use only Mercruiser High Performance Drive Oil. The Seals on these Drives are designed to allow Oil Out to Lubricate them and keep water from entering Drive Housing. With that in mind are you seeing just a very slight loss of Oil? Please keep us posted to aid others who use the Search Function. Al W.
 
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