Johnson 15 re-ring

[thatone123]

I have a Johnson 15 Mid 80's J15RLCOB Had low compression of about 85. Would not start even on starting fluid and it had spark so I thought it must not be sucking fuel into the cylinder? Anyway took it apart and the lower end seems to be good. The wear in the cylinders seems not to be too bad. Question is, Can I just put new rings and no honing or hone it and put new rings of the same size. I don't think it needs to be bored with new bigger pistons?

 

[jimmbo]

When you got 85lbs on a compression test, did you try a different gauge to see if the results were different? If it is not sucking fuel out of the carbs I would be checking the reeds and the crankshaft seals? What condition are the reeds, the reed stops? When you pulled the flywheel off was there oil puddled around the top of the crank?
Any signs of scuffing on the piston skirts? Are the rings free to move in the ring grooves? How did you determine, " The wear in the cylinders seems not to be too bad"? Did you measure the bore, the Piston, and the piston ring gap?
Putting new rings on without honing(deglazing) the cylinder is actually worse than just putting the engine back together with the old rings. The rings and the cylinder wall have to wear in together. New rings on a smooth cylinder wall will never seat thus never seal correctly

 

[Joe Reeves]

Your engine #J15RLCOB is a 1985 15hp Johnson. Actually 85 psi compression isn't too awfully bad, and your opinion of the spark may be at fault.

15 = Hp
R = Rope start
L = Long shaft (20")
C = 8
O = 5 (The C & O indicates the year... 85 = 1985)
B = Factory run number.

Yeah... I know, too late now as you have it apart... but for later use.............

The spark, with "all" spark plugs removed, should be a strong wide blue lightning like flame that will jump a 7/16" air gap... a real Snap! Does it? Note that using the spark plugs to check the spark is a waste of time and proves nothing! If you don't have a proper spark tester, any auto parts store would have one, or you could build the following:

(Spark Tester - Home Made)
(J. Reeves)

You can use a medium size philips screwdriver (#2 I believe) inserted into the spark plug boot spring connector, then hold the screwdriver shank approximately 7/16" away from the block to check the spark or build the following:

A spark tester can be made with a piece of 1x4 or 1x6, drive a few finishing nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere. Use small alligator clips on the other end of the wires to connect to ground and to the spark plug connector that exists inside of the rubber plug boot.

Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:

..........X1..........X2

.................X..(grd)

..........X3..........X4

Deglazing the cylinder walls........The polished look of the used cylinder walls must be deglazed so that a cross hatched pattern exists for the new rings to seat properly... tools exist for this purpose at auto parts stores, Harbor Freight, etc. As a last resort you can use wet/dry 400/600 sandpaper.

After deglazing, wash the crankcase down thoroughly with soap & water, wash it down with the hose, then blow dry it with pressurized air. Oil the cylinders "Immediately" after cleaning as rusting will start to take place within minutes.

 

[thatone123]

Thanks guys, But...I feel real dumb on another one, read on and you will see why> jimmbo mentioned the reeds. When I thought about that for a moment, I said to myself, what reeds? In my haste dissembling the block I did not notice that there WERE NO REEDS!!! I noticed that the innocent soul (lol) that sold me the motor forgot to mention it either. I did notice red silicon gasket sealer on the faces of the block and intake manifold and wondered why that was there, but it did not enter my brain that the reed assembly was completely missing. Seals are good on crankshaft, but yes, there is scuffing on the piston skirt, and yes, I know that me saying that the wear did not seem so bad was kind of a off the wall comment. There does seem to be some light rust in spots along the walls of the bores so I will get one of those engine hones you see in auto parts stores. I have a few 15 parts engines, so will be able to get a reed assembly of from e-bay. That is a good spark tester Joe, when I get the time may make one! I use the type of tester that has a see through tube and you put the plug into the end of the tester. The spark shows as a orange glow in the tube, but it is hard to judge the strength of the spark.

 

[thatone123]

You can't go wrong with these 2 guys as they were both right with the answers. The spark issue was right on also as I found a burned section of the 2 orange wires going to the coil and probably produced a weak spark. BTW...should I use the standard rings to re-ring the pistons? Why do 3 rings come in some packages as I see on some sellers websites?

 

[racerone]

I do not believe that these 9.9 / 15 hp ever left the factory with 3 rings on the pistons !-----What size are the pistons now ?---Measure them with you 2-3" micrometer.

 

[Joe Reeves]

jimmbo mentioned the reeds. When I thought about that for a moment, I said to myself, what reeds? In my haste dissembling the block I did not notice that there WERE NO REEDS!!!.

Hmm.... No reeds or leaf valves huh?..... Well, let us all have time to look in the book to see what that would cause, then we'll get back to you. :lol: Wow... Just when you think you've heard it all... that's a new one!

 

[jimmbo]

BTW...should I use the standard rings to re-ring the pistons?

Oversize rings need oversize pistons
All new rings, even standard rings will most likely need some filing of the ring gap , so don't just install them on a piston and hope everything will fit back together. Measure the gap with the ring in the cylinder. It is important to measure the gap at several locations in the bore, and to make sure the ring is squared in the bore when measuring

 

[thatone123]

Yes, no reeds or reed plate...took a set off another old 15...I think I will buy a complete used set of pistons and crank, hone the block and go from there. Try to measure it also...need to buy a micrometer first.

 

[raczekp1]

hi.
i dont want to have 9.9/15 with compression below 90 psi
here on ebay.com is auction 282812839613. This seler has gasket kit also
i rebuild few motors with those oversize pistons. runs great.
last one wasi in this week. compression oafter rebuilt is 145psi.(10 bar)
2xpiston kit, 2x bearings (auction no 121468301609) and lower bearing 6204 and you get outboard for next 30years.

 

[thatone123]

Sounds great! What I did was order a used set of pistons as I discovered that one of mine has a hairline crack. I honed the cylinder, put the pistons in. One was marked Top piston. When I tighten the connecting rod cap screws past a certain point, I can not turn the crank, but the pistons will go up and down by turning the crank (without the top half of the crankcase on) if I tighten the cap bolts too much????

 

[thatone123]

I did not have a small foot inch torque wrench at the time, now I do. I made those bolts as tight as you can with a ratchet allen wrench. I have them at the right 50-60 ft. inches now. My question is stretching the bolt too much not good. Could I stretch it too much with the allen ratchet. Should I get new bolts? I have heard a few different opinions and want the real skinny on this.