Lower unit oil leak?

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The10Man

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Orlando, FL
The last time I took my boat out was two or three weeks ago. This week I remembered that I forgot to run the gas out of the motor the last time it was in the water.

So today I had to mow the lawn and I decided to run the motor in order to get some the sitting gas out. While I was setting up the trash can under the lower unit I thought I should probably try and burn up the remaining gallon of gas in the tank since it had probably been 4 to 6 months since the last time I put gas in it (I don't fish or run on big bodies of water).

The motor fired up and I let it idle while I mowed the lawn. It was probably running about 15-20 minutes while I was mowing.

Once I finished with my yard work I turned the motor off and as I went to pull the prop and lower unit out of the trash can and noticed that there was quite a bit of dark oil on top of the water.

I'm assuming that this is lower unit oil and the seal isn't tight. If oil got out into the water, I'm guessing that water probably got into the lower unit. I know that water in the lower unit isn't good, but will it cause any longer term damage? How do I go about making sure that there aren't any more leaks? I'm not an expert with outboards and would love any insight or advice on this.
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What kind of motor is it? If its a 2 stroke thats completely normal after that much run time in a tank. If its a four stroke then id say the lower unit is leaking and to check the oil in it


94 xlt 5speed 3.0v6
 
It is a 2 stroke, 99 8hp Johnson.

Wow....I knew that 2 strokes weren't the cleanest, but I thought that just from all the exhausted smoke. I had no idea that 2 strokes put so much oil in the water. That's oil was pretty nasty.

I'm glad to hear though that I don't have a lower unit that need to be fixed.

Thanks for the insight!
 
Agree, that is just waste engine oil (2 strokes only burn about 1/2 of the fuel that goes thru them).

If you never have checked lower unit oil, it would be a good thing to do.

Just loosen the plug at bottom of lower unit. Don't let it entirely fall out. (best to have a pan underneath, JIC) Let a few drops run out, if they are milky or water, there is a problem.

If you want to change the oil (a good thing to do also), then get a tube of the right oil, drain the old, remove the top plug, push in the new from bottom, put top plug back when it runs out the top, then very quickly replace bottom plug. Gloves recommended.
 
CedarRiverScooter said:
Agree, that is just waste engine oil (2 strokes only burn about 1/2 of the fuel that goes thru them).

If you never have checked lower unit oil, it would be a good thing to do.

Just loosen the plug at bottom of lower unit. Don't let it entirely fall out. (best to have a pan underneath, JIC) Let a few drops run out, if they are milky or water, there is a problem.

If you want to change the oil (a good thing to do also), then get a tube of the right oil, drain the old, remove the top plug, push in the new from bottom, put top plug back when it runs out the top, then very quickly replace bottom plug. Gloves recommended.

Thanks Cedar. This makes sense the more I think about it. I changed out the lower unit oil about 9 months ago and I've never noticed any drips from the top or bottom plug or pools of oil below the lower unit.

If 2 strokes only use 1/2 of the fuel that goes through them, I guess this explains why 4 strokes are so much more fuel efficient.
 
Agree with the rest, just going to add 15-20 mins of idle time in a bucket is kinda long(probably doesnt burn as clean at idle).On older gas like that I normally just smell it and mix some fresh with it(if it smells good). I mean you just ran approx. 15 mins and the outboard worked perfect...gas was probably OK. If you think the gas was bad no reason to run it through the outboard.
 
Zum said:
Agree with the rest, just going to add 15-20 mins of idle time in a bucket is kinda long(probably doesnt burn as clean at idle).On older gas like that I normally just smell it and mix some fresh with it(if it smells good). I mean you just ran approx. 15 mins and the outboard worked perfect...gas was probably OK. If you think the gas was bad no reason to run it through the outboard.

Good point Zum. I didn't really suspect that the gas was bad, I just wanted to use up as much as I could so that it didn't sit in there any longer and wouldn't go bad.
 

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