250 Verado Lower Unit Water Intrusion

[Fulch27]

2005 250 Verado serial number 1B056609

Now at ~750 hours. Doing regular 100 hour maintenance for the 3rd time since I have owned the boat. It has been sitting during the winter for 3-4 months. Upon draining the lower unit oil, I discovered I had a ratio of approximately 50/50 water to lube in the gear case. A solid 10 seconds passed of crystal clear water pouring out before any signs of lube draining. I know I should have changed before the winter, but lesson learned....Last time I changed the gear case lube there were no signs of water intrusion it looked great. There was no fishing line around the prop shaft and I check regularly throughout the year. The motor is on a bass boat though and does hit a few stumps etc. from time to time, so I suppose the prop has a few dings and could be a little out of balance . However, this level of water intrusion I have never seen nor were there any prior signs of it. No issues with the gear case shifting, making noise, slipping, etc. I've done some reading already and found a thread where someone with the same issue was advised to drop the LU & change the driveshaft seals, water pump seals, etc and then run for 10-20 hours then check for water in the LU. I would feel confident in tackling this myself, but if it turned out to be prop shaft seals it would mean a trip to the professionals and a bigger time/money investment. Would changing the easier to access upper seals and running it for a while be a wise approach? Or should I just go ahead and bite the bullet and take it in as it is for complete tear down and rebuild? I do have all of the mercury service manuals in hand. I immediately refilled the gear case full with fresh lube after i drained to try and keep the rust at bay and minimize the damage that may already have been done....

Thanks in advance for the advice on how to proceed.

[Fishing Addict]

I'm no expert by any means but, I personally would think you'd be time and money ahead to pressure test the LU before proceeding. This way, if you do discover that it needs to go to the shop, you haven't wasted the time, money, or energy replacing seals that did not actually require replacement in the first place, AND less potential for further, expensive damage.

[BMCD]

Have the pro shaft checked may not be true anymore.

[EuropeanAM]

MOST IMPORTANT: If you have not already done so, refill the gearcase with Mercury or Quicksilver High Performance lube. DO NOT leave it empty if it had water in it.

The correct method of addressing this is to have the gearcase Pressure Tested to check for, and identify the location of, leaks. THEN determine what needs to be replaced to correct the problem.

[Fulch27]

Thanks everyone! Yes I immediately refilled the gearcase with lube to help prevent rust. I dropped the boat off at the shop on Wednesday. They called me yesterday and said pressure test revealed bad prop shaft seals. Its already done and ready to be picked up! I'm going to run it for a while then check the LU to make sure the solution worked. Glad I went ahead and took it in instead of blindly chasing the leak.

Key Takeaways:
1. Always change gear case lube before the boat sits for winter, even if only for a month or 2 :)
2. Change the Lower Unit oil PRIOR TO the Engine oil....otherwise you will waste a lot of that fresh liquid gold dropping the lower, if you run into my situation.