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Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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I have a Nissan NS40D2 outboard. It is a 2002 model I bought

Customer Question

I have a Nissan NS40D2 outboard. It is a 2002 model I bought used. I just replaced the lower unit oil for the first time. Used 16.9 oz 90wt oil. No problem. I put the motor back in the tilt position for the night in the shop. In the morning there was a small puddle of oil on the floor and it was coming from a small hole about 3 inches below the upper oil plug. No leaks from either oil plug. This hole is about the size of a 10p nail. What is wrong? Is this hole for pressure relief? Will water get in the oil case? I have not seen this problem before.
Submitted: 2 years ago.
Category: Boat
Expert:  Jeff G. replied 2 years ago.
It should be a drain hole for the cavities in the gearcase where water normally accumulates. One of a couple things has happened. If the oil is dark, black and smells old then it is probably just some raw fuel that washed down the exhaust and a little dripped out on the floor. If that is it then no real problem other than being messy. When you tilt up the engine some fuel from the carbs spill. NormalIf the oil is clean and like the gear oil you just replaced then you may have pushed some gear oil past a seal or O ring on the driveshaft or shift shaft.You say it is the first time the gear oil has been changed or changed since you bought it? The gear oil should be changed at least yearly. I would also replace the water pump impeller at least every year or two.Let me know what kind of oil it appears to be.
Customer: replied 2 years ago.
Problem solved. Yes it is fresh gear oil. The water pump base block is not bolted down as I am awaiting a new impeller and gaskets in the mail. I had the lower unit attached to the motor with just 2 bolts waiting. As soon as I removed them and dropped the unit an inch or two I saw that the O ring on the base block was exposed (block not seated). I removed the unit and base block a saw lots of oil where it had not been two days ago around the drive shaft etc. Thank you for your valuable advice.
Expert:  Jeff G. replied 2 years ago.
Glad the problem is solved, thanks for letting me help you.

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