never buying another Johnson


Stupid motor only lasted 25 yrs. /sarc

Is piston supposed to look like this?

Appears to have eaten a ring. Inside of head looks like tip of piston.

Old girl ran like a top for a long time. Never failed to get me home. Not one time.

Guess it's time to start researching repower options.


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17' Henry O Hornet w/ Johnson 88 spl
26' Palmer Scott project hull
14' Bentz-Craft w/ Yamaha 25
Replies

i sure wish that was a 1995 ocean runner. i'd buy the whole setup. im looking for a power pack


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Proline 201WA
Aloha 24ft pontoon (LooneyToon)
Old Town stern with 7.5 johnson
Here's a mystery.

That motor on that hull has always done 30-31 mph WOT. I always thought a 90hp should push her better than that but, she ran smoothly, idled nicely, and generally behaved herself if she had clean carbs. Slightly disappointing fuel economy but she's a 25yr old 2-smoker.

Here's the mystery. The last trip, after fishing a spot, 'had a little difficulty getting her to start. She'd spin and fire, stumble, and die. She did it maybe 10 times. Then, got enough start-up lever in her and she fired up and ran. Figuring low speed jets were dirty, I ran her WOT back to the trailer. 31mph.

Second part, on the hose in the driveway, I did a little tidying up of the timing linkage and she went back to purring at idle. I figured since she was warmed up, I do a quick compression test and that was my first evidence of a bad cylinder.

Note that the intake side of the piston face has more carbon build up and there is carbon in and on the dents left by the piece of ring bouncing around in the cylinder. Same is true on the under side of the head.

Question: have I been running on a very weak cylinder for a long time? Curiosity is getting the better of me. I think I'm going to pull the power head and see if I can't get those last two crank case bolts to free up. If I can, will get a piston kit and put her back together. I have no expectation that she'll hold together for very long. But, I'm getting ready to have to buy a new motor. Have been thinking a 115 or larger. But, if a 90 4 stroke will push her near 40mph, I'll save some transom weight and go back with another 90? Decisions... decisions.....





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17' Henry O Hornet w/ Johnson 88 spl
26' Palmer Scott project hull
14' Bentz-Craft w/ Yamaha 25
Here's a mystery.

That motor on that hull has always done 30-31 mph WOT. I always thought a 90hp should push her better than that but, she ran smoothly, idled nicely, and generally behaved herself if she had clean carbs. Slightly disappointing fuel economy but she's a 25yr old 2-smoker.

Here's the mystery. The last trip, after fishing a spot, 'had a little difficulty getting her to start. She'd spin and fire, stumble, and die. She did it maybe 10 times. Then, got enough start-up lever in her and she fired up and ran. Figuring low speed jets were dirty, I ran her WOT back to the trailer. 31mph.

Second part, on the hose in the driveway, I did a little tidying up of the timing linkage and she went back to purring at idle. I figured since she was warmed up, I do a quick compression test and that was my first evidence of a bad cylinder.

Note that the intake side of the piston face has more carbon build up and there is carbon in and on the dents left by the piece of ring bouncing around in the cylinder. Same is true on the under side of the head.

Question: have I been running on a very weak cylinder for a long time? Curiosity is getting the better of me. I think I'm going to pull the power head and see if I can't get those last two crank case bolts to free up. If I can, will get a piston kit and put her back together. I have no expectation that she'll hold together for very long. But, I'm getting ready to have to buy a new motor. Have been thinking a 115 or larger. But, if a 90 4 stroke will push her near 40mph, I'll save some transom weight and go back with another 90? Decisions... decisions.....





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17' Henry O Hornet w/ Johnson 88 spl
26' Palmer Scott project hull
14' Bentz-Craft w/ Yamaha 25Originally posted by PalmerScott




If the block and crank are good...
http://smellofdeath.com/lloydy/piston_diag_guide.htm



The ENTER-NET Fisherman
I got enough stool to work on around here, but, I gots to know why that piston ate the ring.

The cylinder got hot due to the ring failure or some other cause?

If you get apart, I'd like to know if the locating pin failed...or just old rings.

Show me a four stroke that will run with damage like that.




The ENTER-NET Fisherman
Well, here's the problem child. I am absolutely amazed this motor was running reasonably well/smoothly with this in one of the holes. I guess 50 psi compression is more than zero. But, hard to believe.

Obviously, spit out the entire top ring and took a few chunks of the piston with it. Can not believe the entire ring made in into the combustion chamber and got spit out. Didn't get back down into the crank case = would think that would have destroyed everything quickly.

I broke three bolts getting her apart. If I can either get those out or helli-coil them I'll order a piston kit, hone the cylinder a little, and throw all this back together. See if she lasts longer than 5 minutes.






---------------------------
17' Henry O Hornet w/ Johnson 88 spl
26' Palmer Scott project hull
14' Bentz-Craft w/ Yamaha 25


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17' Henry O Hornet w/ Johnson 88 spl
26' Palmer Scott project hull
14' Bentz-Craft w/ Yamaha 25


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17' Henry O Hornet w/ Johnson 88 spl
26' Palmer Scott project hull
14' Bentz-Craft w/ Yamaha 25
Last edited by PalmerScott
that's unreal, thanks for the pictures! Good luck on the rebuild hope it runs another 24 years!
You mention that you thought the boat/motor was slow but OK:

"That motor on that hull has always done 30-31 mph WOT. I always thought a 90hp should push her better than that but, she ran smoothly, idled nicely, and generally behaved herself if she had clean carbs.

I wonder if it was propped right? Just a thought.

https://forums.iboats.com/forum/engine-repair-and-maintenance/johnson-evinrude-outboards/101539-96-johnson-115-piston-head-damage-pics

The picture of the piston that you have appears that the ring locating pin broke loose. The lugging may explain the heat build up. Just a thought. Good luck with the rebuild. Beeswax and heat are our friends.


The ENTER-NET Fisherman
mdaddy,

I've forgotten the numbers, but, I ran a 15 3/4" x 17" prop on her for a long time and she was right below the bottom of the prescribed range for WOT RPMs. About a year ago, I dropped to a 16" pitch prop and it made almost no difference. RPMs went up as expected, but, speed stayed just about the same. Fuel burn stayed about the same. So, I think that means that even if she was a little below the prescribed WOT range, she was doing OK with the 17" pitch.

Regarding the ring locator pin, it is still there and in pretty good shape. It is just around the side of the piston in that pic where you cannot see it. The amount of carbon built up in that top ring lane makes me think this old girl spit that ring out a long time ago. Much of that lane is almost completely full. And, it is hard as a rock. Its been in there baking in place for a while.

Had three bolts that I'd twisted the heads of off and could not get out of the block. After heating gently and shooting with PB Blaster (don't know if the stuff works or not - but, gave it a try) and leaving it for two days. Then, came back, more heat, vise grips as tight as I could get them and got two of the studs out. The third would not budge and I was torquing on it so hard I was a little afraid of ripping a chunk of aluminum out. So, cut it off about 1/8" tall. Filed it flat. Put a sharp felt tip dot in what I thought was the center. Center punched the dot several times to give good dimple and started drilling with a very small drill bit. Stepped up right through the bit set until I started to see the hint of threads in the wall of the hole. Ran a tap through the hole and it cleaned out nicely. I've tried to do that trick dozens of times over the years. This is the first time I did not end up having to over drill and heli-coil or re-tap it. Very Very lucky.

So, ordering a piston kit and a variety of gaskets. When the parts arrive, I'll put her back together.

Once I get the piston in, I'll hook a drill motor up to the top of the fly wheel and spin her slowly, feeding her 2-cycle oil in the cylinders for a few minutes to make sure nothing catches an edge with the new rings. Then, maybe speed up and spin it with the drill for 10 minutes or so.... feeding oil the entire time. If everything is smooth and stays smooth, put her back together. I think if she runs 2 minutes, she may run a long time. She may not run 2 minutes. We'll see :-)

Should start a pool on how long she runs.
I'll buy the winner a beer. (Or, maybe the winner should buy me a beer. ;-) )



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17' Henry O Hornet w/ Johnson 88 spl
26' Palmer Scott project hull
14' Bentz-Craft w/ Yamaha 25
If you got skills a rebuild should last as long as the original or longer. 2 smokes are built to be rebuilt. I'm sure some other things will take a dive since they are 25 years old
There's an art to working on junk. I like your dedication and tenacity. They be in short supply in most cases.

Now, what is this???:



Bolts break...no mater what. Feels good when you drill one out right. I don't know which works better about loosening agents. I like watching the wax get sucked in. PB blaster seems to work...wax isn't as flammable...so there's that.

The picture looks like a locating pin stuck to the piston... Or cracked up through. Either way, find a good machine shop to check the block and crank since it's apart.(Nice to have other eyes depending on price and you having micrometers)

Considering your drive to fix something, I'm in the pool !!!!!!... that with that motor done right... might outrun you.

Enjoy your work.




The ENTER-NET Fisherman