1988 Johnson 150HP black oil residue

[mstahl1171]

My 150 started spewing black oil out of the top exhaust ports yesterday after a good 4 hour run. The residue is a thick blackish / brown oil that has the consistancy of of Maple Sryup. What could cause this? Im thinking maybe carbs or VRO? Any thoughts?

 

[Bosunsmate]

Check your plugs

 

[mstahl1171]

Plugs looked normal..nice brown color....have good spark. Just installed a new power packs, coils and plug wires in the spring.

 

[Bosunsmate]

Hows it running?
Maybe your exhaust housing is blocked and needs a clean,
Maybe its overheating and suddenly melting all the exhaust residue.
Just some thoughts

 

[mstahl1171]

It run great...idles well and has no issues at any rpm range. Water temp stays around 160-180 if the gauge is accurate. Does not smoke. I have done a decarb back in the spring. I can't complain about this motor at all. Maybe I'll do another seafoam treatment and see if that helps. If not...I'll pull the boat and drop the lower unit and see if there is blockage. Ive got good compression, no VRO alarms, Carbs were rebuilt in the spring time.

Ive seen motors where the gasket between the power head and lower unit fails and you get a leak all around...but this only seems to be out the top exhaust ports. Maybe the gasket has failed?

 

[Bosunsmate]

Ive seen motors where the gasket between the power head and lower unit fails and you get a leak all around...but this only seems to be out the top exhaust ports. Maybe the gasket has failed?

Maybe. I think those gaskets are meant to be done every three or four years but most never are.
My gaskets gone and i get a bit dripping down the side of the leg, but nothing like what you mention.
It sounds like it must be accumulated stuff leaking out if your motors running fine and plugs are all clean, Sometimes the exhaust base can corrode out and send exhaust in different directions.
You could drop the lu and have a look up there with a torch, hard to tell what exactly caused it without lifting the powerhead.
I doubt its anything to do with the vro as your plugs would be looking black and the engine would be smoking

 

[boobie]

As long as it's running good take it out and run the heck out of it and see what happens.

 

[emdsapmgr]

Did you recently have the impeller changed out? It's possible that during reassembly, the tech did not install or mis-installed the two exhaust gasket/o-rings on the lower exhaust housing. These orings help direct the exhaust out the prop. If one is missing, or was mis-installed, exhaust gas can leak into the inside of the midsection. Might even migrate up into the two exhaust relief ports. Probably not a fatal problem, but if the lower one is missing, hot exhaust might get directed towards the nearby plastic impeller housing-and that could reduce the life of the water pump.

 

[mstahl1171]

Yes...I did change the impeller back in the spring of this year. I went out again Tuesday and ran it hard...came back...still loads of black oil residue. Pulled the plugas again...and wow. all looked fine except # 1 cylinder....dark black carbon deposits. I also check compression on all cylinders. All were around 92psi except #1...which was 50psi. Sounds like thats the problem or part of it. I hope its just a gasket and nothing worse. Will pull the boat this weekend and remove the head....ugh

 

[mstahl1171]

Update: So before I tear the motor apart, I decided to try a can of seafoam mixed with one gallaon of fuel. Ran the motor on that till it smoked the neighbors out and burned a whole gallon. Let it set over night and repeated 2 more times. WOW...what a difference! My engine still leaks a little of the black oily residue but nothing like before. Also the compression on #1 cyl is now 78psi vs 50psi before treatment. I am going to run some Yamaha Ring Free thru it this weekend and see if that helps. I also ordered a VRO rebuild kit. Figured I might as well do that too. I must say....it idles and runs even better than before...and much quieter. So maybe my VRO was pumping too much oil? Carbon buildup on rings and reeds? So far so good.

 

[racerone]

Might as well removethe wee bypass cover for # 1 and look at piston and rings.-----Just 6 small bolts and a $2.00 gasket.

 

[mstahl1171]

Racerone....yes...i forgot to mention that I have the gaskets and will remove the cover and inspect. I'll keep you posted.

 

[mstahl1171]

No Title

So i finally got around to tearing the heads off of the 1988 150HP. Found that one cylinder had a ring failure and blown head gasket. The rest of the motor looks great. I hope to get this done before April. Will also do a complete paint job and new decals

 

[racerone]

This is not surprising to me !

 

[emdsapmgr]

That bad piston looks pretty shiny. As if the aluminum has been delaminating. Possible lean condition. You may want to pull that top carb apart and check the main and mid jets to be sure they are not restricted. If not corrected prior to running after overhaul, you could wind up with the same problem. The placement of the rubber water diverters looks ok. Your running temps are too high. The stats in each head should regulate the water temps to 143-155 at idle. Your observed temps are too high for long term running. An overheat horn comes on at around 205-212 and shuts off at 175, ( so normal running at 160-180 is still too high) A lean carb condition, coupled with a hot running powerhead would yield the failure you have pictured.

 

[mstahl1171]

Good to know emdsapmgr. I have ordered all new gaskets, piston, carbs kits, thermostats...etc. My warning horn works...but never had an overheat. I know the wiring was good a few months ago but will check again. I will chect the temp sensors. Maybe it's bad? I know I can boil the stats to see if they open. How about the sensors? Can you heat them to see if they work?

 

[emdsapmgr]

The fact that you did not get an overheat warning is not unusual. Once cyl can overheat internally (due to a lean fuel condition) and if the cooling system is functioning properly-you will never get a hot horn. All the more reason to determine just what caused the current (lean condition) failure. The factory service manual has a procedure to test the overheat temp switches. Similar to checking the thermostats. It involves boiling automotive car oil with a temp switch inside, connected to a flashlight. The light should start to glow (light up) at 211 degrees. The continuity will "go open" (light go out) when the oil cools down to 175 degrees. These are in series, one on each head. Keep in mind that when your boat gets up on plane, the pressure relief valves in each head will be forced open, flooding the powerhead with extra cooling water. The powerhead temps can go down over 20 degrees or more when on plane. When compared to the above mentioned normal idle temps.

 

[mstahl1171]

Thank you emdsapmgr!...now it makes sense. I plan to tear the carbs down once I get the rebuild kits. A friend told me about a ultrasonic cleaning system at his shop that cleans parts /carbs with a solution similar to Simple Green. Suppose to do a super job and not does not use harsh chemicals. Have you or anyone else used? Know if it is okay to use on a marine carbs?...just curious

Thanks again guys

 

[emdsapmgr]

The only thing to ask about in that ultrasonic system, is if it will dissolve dried fuel gelatin. Not all liquid cleaners will handle dried fuel.

 

[mstahl1171]

I'm having trouble removing the flywheel nut. The shop manual says to use a strap wrench to hold the flywheel. I have been unable to find one large enough locally and might have to order online. Is there another trick to hold the flywheel while removing the nut?