Yamaha outboard 2 stroke spilling oil lower unit

[AirJonn]

Hi all,

I just recently bought a Yamaha 5BS 5hp 2 stroke outboard. After one hour of perfect running it stopped completely. Did clean the carb but no luck.

One thing I am worried about at the moment is that when you pull the cord to start the engine, oil is leaking from this hole at the lower unit, see image. It even seems to spray a bit.

Is this normal or did I buy a piece of junk? Might this be a hint why it wont start anymore?

Any help would be really appreciated.

Greets John

[tkeithlu]

Welcome to the forum, John.

The leaking oil sounds like a bad oil seal on the lower unit. That's not surprising, given age and suspected long storage. A parts manual would help you there; the repair is not difficult or expensive.

The sudden stopage suggests a clogged fuel ine, because the supply of air, compression, and spark are not likely to have changed. The one that could have changed would be spark, but it's not as likely as fuel.

The easy first tests involve pulling the spark plug after trying to start it. Is it dry? If so, fuel was not there. Second, do you have a spark? You can test that by taking the engine into a dark area, grounding the threads to the plug, and pulling the starter. You should get readily obvious and regular sparks across the plug.

Final thought: Have you checked the kill switch? Sometimes they grow stiff with age, usually resulting in running, but it could have stuck in the wrong position.

[AirJonn]

Hello, thanks for looking into my issue.
The spark plug was not dry, very wet and black. It does spark though after cleaning.

I was going to replace it anyway, so I went to the boat shop to get one and I showed them the same picture. They immediatly told me to throw away the engine, the hole is not supposed to be there and very concerning with the oil They told me the engine is totalled and I should not try to fix it.

They didnt even give me the spark plug haha, so sad. I guess I am going to have to look for another engine, this time much newer and knowing a bit better what to look out for hopefully.

I might try to get a old spare part for the tail one day and try to replace it. Ill update.

Thank you very much.
Cheers, John

[Sailmonkey]

I’ve got the same hole in my 2 stroke mariner outboard.

What oil is your engine spitting out there? Is it black and dirty? Or is it clean gear lube?

What mix of oil/gas were you running through the engine? The plug fouling sounds like too much oil in the gas.

I wouldn’t condemn this engine yet. Put a new plug in it and run it.

[AirJonn]

Same hole really? I'm so confused haha. Sounds good though.

It is black and dirty, not clean at all.
Running 1:100 but there was some gas left in the tank from who I bought the motor, I should have dumped that.

Ok got some hope again. Going to clear out the tank and get a new plug. Lets see what happens.

[clownfishsydney]

Originally Posted by AirJonn

Same hole really? I'm so confused haha. Sounds good though.

It is black and dirty, not clean at all.
Running 1:100 but there was some gas left in the tank from who I bought the motor, I should have dumped that.

Ok got some hope again. Going to clear out the tank and get a new plug. Lets see what happens.

I would have thought that 1:50 was what was needed, this is what most premium 2 strokes have as minimum.

[Gary Mc]

My son has an 8 hp 2 stroke Yamaha and had issues with it running, I believe he found there was an in line fuel filter that was plugged. Worth checking into.
Good Luck

[Sailmonkey]

Originally Posted by AirJonn

Same hole really? I'm so confused haha. Sounds good though.

It is black and dirty, not clean at all.
Running 1:100 but there was some gas left in the tank from who I bought the motor, I should have dumped that.

Ok got some hope again. Going to clear out the tank and get a new plug. Lets see what happens.

That hole is there to drain the drive leg above the lower unit. Black gooey oil is from the exhaust. Likely running rich and not completing combustion.

[BillKny]

Originally Posted by Sailmonkey

That hole is there to drain the drive leg above the lower unit. Black gooey oil is from the exhaust.

^^^^^THIS^^^^^

The hole is most certainly SUPPOSED to be there. Your local outboard shop is either a collection of incompetent fools or a bunch of crooks out to sell you a new engine by lying to you. I have my money on the second choice.

One of the biggest issues with these small 2-stroke engines is leaving fuel in the carburetor, which then clogs up the low speed jets when it evaporates and leaves goo behind. This is an easy diagnosis because the engine will start with the choke, and run at half throttle or above, but quickly stall at idle. Cleaning the carb should be on your list of things to do to bring this back to life.

Be sure to run out the fuel from the engine if you aren't going to use it again that day and you'll never have this problem.

If you have any concerns about the seals in the lower unit, just change the oil there. You'll see water if there is any.

[AirJonn]

It is running !! Yessss

Wow a huge huge thanks to Sailmonkey, tkeithlu and everybody else, you quite literally saved this engine for me.

Originally Posted by BillKny

^^^^^THIS^^^^^

The hole is most certainly SUPPOSED to be there. Your local outboard shop is either a collection of incompetent fools or a bunch of crooks out to sell you a new engine by lying to you. I have my money on the second choice.

Yes this is pretty disturbing. I will not be going back there that is for sure. They indeed tried to sell me a new 4 stroke right after.

What I did, I cleaned the carb once again.
Installed new spark plug (noticed the old one had a too large gap not sure how big of an impact this has - 0.95 vs 0.7).
Cleaned tank and hoses and added fresh gas.

It started at second pull. Runs beautifull.
And, no more oil coming from the hole.

Originally Posted by Sailmonkey

I wouldn’t condemn this engine yet. Put a new plug in it and run it.

This. Thank you!!