Johnson 100hp white and blue smoke

[Ma87k5]

My Johnson is blowing blue and white smoke while in the water. And runs rough and bogs down. I changed fuel pump, spark plugs, rebuilt carbs and fresh gas oil mix. No change. All cylinders show 120 psi. Top 2 plugs show clean while bottom 2 plugs show slight carbon build up. Could it be a cracked block? Thank you

 

[racerone]

Year ?----Model # is ?-------I believe you are overthinking this issue.

 

[thatone123]

They call it smokey joe 2 stroke....best outboards ever made!

 

[Ma87k5]

1992 gt 100.

J100STLEN​

 

[Bosunsmate]

check your spark plug electrodes

 

[Chris1956]

White smoke is usually steam. Steam is not very normal at this time of year. Blue smoke is oil...normal all times of year.

 

[Ma87k5]

It started to bog down last year just as I came into an outgoing breachway at the ocean. I was barely going fast enough to go against the outgoing tide. Didn't stall at idle. Didn't smoke at all then. Just bogged down when I gave it throttle. Now it smokes. Can't upload vid of running engine. Wrong file extension. Thank you for your help.

 

[JerEazy]

When you run it on the hose, does it smoke like crazy? Black/brownish stuff coming out of prop exhaust?

checked spark? Resistance on coils?

doubtful on the block if the compression tested even like that.

 

[Ma87k5]

I don't remember anything black coming out. On the hose it doesn't smoke white either only blue.

 

[Ma87k5]

[No message]

 

[JerEazy]

Looks relatively normal to me. Maybe run a decarb and see if it improves?

 

[Joe Reeves]

As per post/reply #6..............
Blue smoke = oil
White smoke = water

 

[Bosunsmate]

Sounds alright to me

 

[Ma87k5]

It is at full throttle. Never smoked before. Only on start up. Never could leave it running at full throttle using the hose. Thank you.

 

[Joe Reeves]

Running at full throttle on a flushette (no back pressure) or neutral in any scenario, you are exceeding the engine's rpm rating by far and inviting a runaway engine whereas it actually becomes a diesel!... Turning the key to OFF, yanking the plug wires off, does absolutely nothing.

Clogging the carburetors off from their air flow will stop it if you had the carburetor face plate off, and if you could stand to get that close to the screaming meamie before it explodes. Something to keep in mind..........

 

[Ma87k5]

Ok. Let me try to explain this better. The video is with the lever at full throttle. If it was running normal I would not be able to run it at full throttle unless I was on the river. I did say when I give it gas it bogs down. The rpm is no where near maxed out. The engine didn't even get close to overheating. I used to be able to rev it up to full and max out the rpm for a split second before bringing it back down. I've had this boat and motor for 7 years. Used to push the boat up to 42 mph. Now maybe 5 to 10 mph. Always was a reliable engine. I'll post a pic of the spark plugs tomorrow to show the issue. Thank you for all your help.

 

[JerEazy]

Something doesn’t add up. Confirm compression numbers?

 

[Joe Reeves]

If that engine runs normally at idle and bogs down when you give it throttle, that's usually due to a sticking timer-base under the flywheel or a clogged, fouled carburetor. Your mention of the top cylinder having clean spark plugs leads me to question that top carburetor.

Check the condition of the 2 high speed jets in that carburetor. If they're fouled, that'll do it.

Also... I don't see any mention about the spark which, with all spark plugs removed, should jump a 7/16" air gap with a strong blue lightning like flame... a real SNAP! Does it? NOTE that the 7/16" air gap is important.

 

[oldboat1]

Any chance of a problem with the throttle cable? Might try detaching the cable at the motor and throttling up at the motor, keeping in mind the safety limits when running on muffs.

 

[Ma87k5]

Dang forgot to add. After I start it and let it idle, it will stall after about a minute or so. Thank you again.