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My 1989 9.9 4 stroke yamaha has smoke coming out of it and…

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Hi. My 1989...

Hi. My 1989 9.9 4 stroke yamaha has smoke coming out of it and some black gunk coming out of the exhaust.

Mechanic's Assistant: Sometimes things that you think will be really complicated end up being easy to fix. The Marine Mechanic I'm going to connect you with knows all the tricks and shortcuts. Tell me a bit more about what's going on so the Marine Mechanic can help you best.

Last year I had an issue with the engine sputtering when hot. So I cleaned the carb. very well, twice, and that problem is gone based on tests in a test tank (cold water). But now it's smoking white and leaking black gunk through the exhaust outlet. Checked float and it's at a good position, as is the pilot screw. The gunk is really sticky and gross. Very hard to wash off. Engine is having a hard time idling too - has to be set somewhat high to idle.

Submitted: 24 days ago.Category: Boat
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Customer reply replied 24 days ago
Also I noticed that the gap on the lower spark plug was a bit small (also their was black soot on it). I can't re-test it since it's too cold out tonight and it's really hard to get the motor outside into the test tank.
Answered in 10 minutes by:
3/31/2018
Marine Mechanic: Jason, Marine Mechanic replied 24 days ago
Jason
Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 16,770
Experience: Degree in Marine Technology. Gas and diesel marine mechanic.
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H​ello my name is ***** ***** am I speaking with? I read what you wrote. Are you able to compression test the engine?

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Customer reply replied 23 days ago
Hi Jason, this is Jeremiah. New on JustAnswer. Thanks.
I haven't tested it this spring, but in the fall it has 119 and 110 on the two cylinders. Can't remember which was which. I was testing with a normal prop in a test tank. Not sure if that high load would cause smoking. It is a high thrust motor.
Marine Mechanic: Jason, Marine Mechanic replied 23 days ago

HI Jeremiah. You would want to start with a compression test. Also, can you pull the spark plugs out and see if either of them have white or like new looking inner insulators?

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Marine Mechanic: Jason, Marine Mechanic replied 23 days ago

Also, how old is the fuel itself? Are you running the outboard off of a portable tank, or is the tank built into the boat?

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Customer reply replied 23 days ago
I'll have to get a comp tester. Upper plug is grey. Lower is black sooty and wet.
Customer reply replied 23 days ago
Fuel is new prem ethanol free. External portable tank. I think a little air is getting in the fuel due to an imperfect seal.
Marine Mechanic: Jason, Marine Mechanic replied 23 days ago

Good morning. Lets see what happens when you compression test it. Also, what is the model number on this outboard as it reads on the ID tag?

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Marine Mechanic: Jason, Marine Mechanic replied 19 days ago

G​ood morning. Just checking in. Did you get that compression test done?

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Customer reply replied 19 days ago
I just got the compression tester in the mail yesterday and tested it this morning. 118 on the top cylinder, 110 on the bottom. The bottom plug is the one that was black and wet though. It was also the plug that was under-gapped. Do I need to check the valve gap?
Marine Mechanic: Jason, Marine Mechanic replied 19 days ago

Got it. The compression reading is to low. This engine is either going to be worn out, has cylinder damage, has bad valves, or needs a valve adjustment. The minimum compression spec that is printed in the service manual is 139 psi. That would be the minimum. Basically from here you would need to pull the head cover off and check the valve clearance, and adjust it if it is not in spec. Then retest the compression and see if it comes back up or not. Does that make sense.

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Customer reply replied 19 days ago
I'm looking at the service manual now. Spec. is 114 psi. There's a note that anything more than 85% of spec. (i.e. 97) is fine. See attached files. I don't see anything in there about this, but I've always been told that the cylinders also need to be within 15 psi of each other, which they are.
Marine Mechanic: Jason, Marine Mechanic replied 19 days ago

M​y book says 139, but I am also guessing as to what manual I need to pull because I never got your engine model number. What is the model number on your outboard as it reads on the ID tag?

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Customer reply replied 19 days ago
FT9.9 EXF It's an 89
Marine Mechanic: Jason, Marine Mechanic replied 19 days ago

O​kay got it. I was looking in the wrong manual. This black gunk that you are seeing is likely carbon buildup. Go to a Yamaha dealer and get a can of a product called "Ring Free". Ring Free is an engine decarbonizer. Follow the instructions on the can and run the decarbonizer through the engine. This will blow more black stuff out, but it should blow it all out. Let me know how you make out.

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Customer reply replied 19 days ago
I'm confused. I thought carbon buildup was generated slowly and adhered to the inside of the engine (e.g. there's a thin, hard, brittle coating of on the head of my lawnmower piston).
In the outboard I was getting large amounts of a soft black gooey substance sticking to the outboard shaft and white smoke. The goo has the color and consistency of grease. I'm tempted to think it is grease (new zerc fittnig) except that I was also getting all that smoke and the black gooey trail starts at the upper exhaust outlet. Here's a pic (attached), though mostly cleaned off. A video of the smoke is here: https://photos.app.goo.gl/V3TXnFu77JrXHE9q2
Could that be carbon buildup?
Marine Mechanic: Jason, Marine Mechanic replied 19 days ago

T​he gunk can only be carbon or oil. Have you ever laid this outboard on the wrong side?

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Customer reply replied 19 days ago
I did lay it on the wrong side briefly when getting it into the test tank. I let it run on high for 45 minutes and it was still smoking - would laying it wrong have smoked for that long?
I had suspected that it could be oil or unburned gas that was getting into the exhaust because I was running at high throttle and very high load (test tank) with a poorly gapped spark plug. Guessing it never hit 3000 rpms. Is it possible that could have been the cause? A test on the boat (once it's warmer out) would confirm that I think.
I can get some ring free in any case. Thanks!
Marine Mechanic: Jason, Marine Mechanic replied 19 days ago

I let it run on high for 45 minutes and it was still smoking - would laying it wrong have smoked for that long?

​Well... after 45 minutes it really should have cleared out. It is possible the engine is burning oil due to worn rings or bad valve seals as well. But I would run the ring free through the engine first and see what happens. The Ring Free will blow out all oil and carbon buildup out of the combustion chamber. If she still smokes bad after running the ring free through the engine. First just check your fuel, and make sure there is no water in it, or run the engine off of a tank that is filled with brand new fuel. After that, if it still smokes, then it's burning oil.

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Customer reply replied 19 days ago
ok thanks. I'll try ring free.
Marine Mechanic: Jason, Marine Mechanic replied 19 days ago

You are very welcome. Let me know what happens.

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Customer reply replied 19 days ago
Sorry one last question. Does it have to be Yamaha brand Ring Free or would something like sea foam (or another generic brand) work?
Marine Mechanic: Jason, Marine Mechanic replied 19 days ago

Seafoam is really to weak. If you have a Mercury or Evinrude dealer nearby, Mercury makes a product called Power Tune, and Evinrude makes one called Engine Tuner. Both of those are on par with Yamaha's Ring free, and they are all 100X stronger than Seafoam.

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Marine Mechanic: Jason, Marine Mechanic replied 19 days ago

I do want to make sure you are happy with my service before you go. If you had a further or more specific question on the issue by all means feel free to ask. If not, Just in case you do not understand the way the website works (and some folks do not). You do have to put forth a positive rating in order for it to credit me for helping you. When ratings are not done, the website simply keeps your deposit and they will not credit me. The ratings box is located at the top of the screen. To rate, you must select the star you wish and also confirm it. Please let me know if you run into any problems or errors when trying to do it. If you do have a problem, or if you can not see the ratings box which is at the top of the screen. Please reply back "I rate Jason's service _______" and fill in the blank.
Questions do not close out, so if you have to come back later on with follow up questions to the issue you still can even after doing a rating.
Thank you

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Customer reply replied 19 days ago
Ok thanks. I'll make sure to do that once we've resolved the issue.
Marine Mechanic: Jason, Marine Mechanic replied 19 days ago

Y​ou bet. Keep me posted.

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Marine Mechanic: Jason, Marine Mechanic replied 12 days ago

H​ello. Just checking in. I never heard back from you. How did you make out?

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Customer reply replied 12 days ago
Hey Jason, I was able to check the gap on the valves. It was too small on three of four of them. Would that cause smoking?
Haven't gotten to test it again (bad weather).
Marine Mechanic: Jason, Marine Mechanic replied 12 days ago

If the valve adjustment was not correct that can cause smoking. Whether or not it's the cause of the smoking on your specific engine remains to be seen.

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Marine Mechanic: Jason, Marine Mechanic replied 7 days ago

Hello. Just checking in. How we doing?

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Customer reply replied 6 days ago
Hi Jason, we've had a long string of awful weather, so I haven't been able to test it again. Hopefully this next week I'll be able to.
Marine Mechanic: Jason, Marine Mechanic replied 6 days ago

Okay keep me posted.

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