Mercury 115 1981 Tower of Power - gas in exhaust and excessive smoke? [with video]

[ColdWeatherBoater]

Hello Everyone!
I just got a new (to me) boat and the motor has not been started in 15 years. It's a 1981 6cyl mercury 115 tower of power. I rebuilt the three carbs, rebuilt the water pump, drained the gas and oil and refilled it, and just generally cleaned things up. Started her up and she runs! I wanted to check on a few things I was worried about and see what the experts think:

1. The exhaust water seems to have either oil or gas in it in a fairly significant quantity. In the video below you can see what it looks like, my guess is gas but it's hard to tell. Am I just running really rich or could this be a bigger problem?
2. It smokes quite a lot. I think this is because I was pretty generous with the oil ratio. Or is this amount of smoke normal?
3. Does this seem like a pretty rough idle?
4. There is a small oil leak out the bottom of the lower unit when the motor gets turned off. It's black oil. I just put fresh oil in the lower unit so I'm not exactly sure what that is. Any clues you could give me to look for?

Here is a link to a video of it running: [this is after it was running for about 20 minutes]

Thanks in advance!

 

[merc850]

The oil/gas ratio is 50:1 more oil is not better, it sounds like a good idle on land but you can adjust it when it's in the water-in gear at 1300rpm. Do a compression test to make sure that all cylinders are up to spec. If you have a timing lite put it on each spark wire to see if they are all firing. It's possible that the LU needs resealing; under the waterpump and the shift-shaft bushing and replace the screw gaskets. I use Amsoil at 70:1 which produces very little smoke and water contamination.

 

[Chris1956]

Stick with TCW-III rated oil. At last check, the Amsoil is not TCW-III certified. Run the motor at 50::1. It will run best with fresh 50::1 fuel.

​As for your video... the motor is running fine. It is a bit smoky, but at idle, after 15 years on non use, I thought it was fine. I assume you set the carb float heights correctly?

​You might check or rebuild the fuel pump. If the diaghram leaks, you will see fuel in the exhaust and more smoke than usual.

As for the oil drip. Smell it. If it smells like gas or oil, it is 2 cycle oil and normal. If it stinks like gear oil, you likely have a leak in the gearcase.

 

[merc850]

Saber Outboard is TCW-3 rated ;(it's good for 100:1 or any ratio in between), Saber Professional isn't TCW rated

 

[jimmbo]

There's going to be unburnt gas and oil in the exhaust water, just the nature of the beast, especially at idle. It appears to be idling quite well, that might change once it is sitting in the water. Adjusting 3 carbs is not really my idea of fun, but it will need be done as your initial settings are probably rich. Most of what you are calling smoke looks like condensation. Water is a product of combustion. Think of any excess smoke as Mosquito Control. Just use a good TCW-3 oil(Mercury and BRP are good examples) @ 50:1 and the engine will live a long life. Bearings that turn smoothly with 50:1 do not turn smoother with 40:1, 24:1, or even 16:1. That engine needs oil to complete a Labyrinth Seal on the reed blocks, so less than 50:1 is not a good idea.

 

[roscoe]

but you can adjust it when it's in the water-in gear at 1300rpm. .

1300 ?
Mine is about 800

 

[merc850]

I have mis-posted the low speed adj. it is done at 800-900 rpm.