e-Bay Project & Why it Blew a Piston After Rebuild



submerged outboard motor recovery


History :   This is the story of a e-Bay purchase, which turned out to be not quiet what it was advertised, and the problems I had in finally getting it running right.   This is a 1994 9.9 Johnson 2 cycle.  When I bid on it, I was sure that it would need some repairs, but not to the extent that finally materialized.


The seller (from Texas and obviously not an outboard motor person) in his listing, mentioned that he had run it the week before, however he said that his friend, (whom he got it from) had robbed the powerpack off to try on another motor, but that it was not the same so he had not taken the time to reinstall it.   It had sat for a couple of years when the seller got it, but he did not have the time to put it back together.   His picture (1) of the motor was not that good, rather dark so you could not really see everything.   It was a 1994, 2 cycle, short shaft, manual starter version.  Just what I wanted in that this was into the newer series big block motor that I had never seen up close before, and it need some work which I was capable of performing.


When I got it thru UPS, the shipping container was simply a large cardboard box that the motor was stuffed into, no packing or strapping at all.  The motor was loose inside, the rear upper cowling latch was broken, the LH lower cowling was cracked, the decals were scratched badly, the manual starter was missing as was the prop and nut.   I immediately called him, asked about the starter.  His quick reply was, "well you got what was pictured on the add".   Yah, but kind of hard to argue with his using a bad, dark, out of focus picture and the fact that he was clear across the country and he already had my money order.   I asked him if his buddy still had the starter as I was going to have to buy one and I might as well get it from him as used parts for this later motor were not very plentiful.   3 days later he called back but said his buddy did not have it.


Me, being a pretty honest person, gave him the benefit of the doubt, thought, well maybe he had used a rope wrapped around the flywheel to start it.   Later found out I was WRONG.   Another thing that I did not grasp initially is that he said the buddy removed the powerpack, was with the motor but had not put it back on.   Well this motor has what is known as an UFI (Under Flywheel Ignition)  if this information was correct, then the stator and powerpack combo would have not been in place on the motor, which it was there.


Found Used Parts on e-Bay :  After looking for about 5 months and loosing the bid on one starter assembly, I finally bid high enough to get the next one that came up.   I now tried to start it, but not even a pop.  Then tore off the carburetor, cleaned it, but it had FINE brown dust in it.  OK cleaned as much as I could and blew it out with compressed air.  Looked good to go.  Still not pop.


I the meantime I had priced a new lower cowling, WOW,  $120 for just one side.  I tried to use plastic epoxy on this thing, but to no avail.  So I used an 1/8" aluminum strip, made a external band that I bolted on.  Not pretty but it held the plastic cowling together.  I finally moved it from the outside to the inside by lots of hammering, forming to fit the curved rear section, with only the bolt heads showing, much better.   Later bought a new plastic latch for $16.


Left side lower cowling repair


About that time someone on e-Bay was parting out a 98 of the same series.   I bid and got the complete lower housings, (both RH & LH) and the top cowling.  This was good as the latch had been improved so my newly purchased one was now of no use to me.  I also got the complete flywheel and stator assembly for a electric start motor plus a starter switch (which later proved defective).  I let the electric starter go when the bid got near what I eventually paid for a new one.  Now I had all (I thought) the makings for a newer electric start motor.   I found that these newer motors differed from the pre 93 motors in the electric starter in that they now use a starter solenoid, a simple starter push button that engages the starter switch which entailed more expensive parts.


More Discoveries :  In tearing off the stator, I found the same FINE brown silt up under things that should in all normal operations would NEVER have been subject to it under any conditions.  I then got to thinking that this motor came from Texas, possibly was sunk during a hurricane & maybe it was salt water, also which prompted me to pull the head.   Bad, as the complete lower water jacket was solid with salt corrosion. 


In photo below you can see all the salt corrosion in the water jackets between the cylinder walls and the outer block walls.  This corrosion was so hard that a hand drill motor and a 1/8" drill bit was used to rout out the RH side only of the lower cylinder in this photo.   With the accumulation of this corrosion laying at the bottom.  The whole LH side water jackets are solid corrosion.  The cylinders are rusty, lower ring stuck on #2 piston, compression was better than expected however.


It is hard to understand why this motor was not flushed after usage in saltwater, as it is a 1994 that has a factory flush plug made into the upper top of the water jacket cover with the word "FLUSH" near it.   Possibly just laziness, didn't know or didn't give a darn.  The pile of white dust at the bottom of the photo is dried salt/aluminum that came from the water jacket of the RH lower cylinder area only.  Left side and top cylinder walls to go yet.


The motor below  as described above.


Maybe I had better now look at the crankshaft before I go any farther.  I have already got lots of money invested and possibly for something I am going to have to part out, then sell on e-Bay also.


When I got inside the motor, surprisingly enough the crankshaft was OK, it had some slight discoloring on the bearing journals but no evidence of corrosion or pitting.   While I had everything apart, I honed the cylinders and re-ringed it.   The bearings were OK as was the crankshaft seals. 


In reassembly I must have been sleeping as in reassembly of the reed valve plate between the block and manifold, I put the wrong gasket, (manifold) on the rear side of the plate.   Both of these gaskets are very similar except the opening for the reed valves.  Got it all together but could not get the motor to even pop by squirting a little starting fluid into the carburetor.  Cranked until my arm gave out many tries, over a few day period.   Thought about it many nights and finally decided it had to be in the reed valve plate assembly, so I tore the manifold off.  What I found was as said before, the gaskets were reversed which meant the front gasket being at the rear had smaller openings for the reed valves.  This gasket now had held the reed valves closed.  Hell yes, no fuel could get past the reeds.  


OK, Now it is Running & I'm Fishing :  It is now running, but it seemed a little cold blooded as I had to choke it most times to start even when warm.  Since this was a newer motor that I was not familiar with, I kind of accepted that fact, but tried to adjust the carburetor.   After I got the carburetor adjusted, it trolled OK.  I trolled with it 3 full days for a total of about 24 hrs fishing for salmon in Hood Canal.  The next week I went to Willapa Bay, again for salmon, trolled for another 5 hours when it quit.  


Main Motor Died Same Day :  This motor a 70hp jet was just used as a "get to" motor, but in between all the other 9.9 confusion, the 70hp died of what was later determined to be a dead powerpack.   So we had to rely on the now dead 9.9.


Something Happened :  Since the 9.9 was now our only source of locomotion, I changed to new spark plugs and it ran half-heartedly enough to get us part way back to the boat launch and died again.  My fishing partner asked if it would run on only 1 cylinder, yes it would.  At that point, while running,  I pulled the bottom plug wire, no change, it just kept running the same.  We shut it off, pulled this bottom plug, the electrode was smashed flat against the center electrode.  Was this a defective new plug, had we dropped it before installation?   There could not be anything wrong with this motor that had only about 30 hours on a rebuild.  Changed to another new plug, and made it back to the launch at 5 MPH instead of the previous 3.5 MPH with the smashed plug electrode.


Phone Call to Shop :  On the water, I called the marine shop I deal with, he had a new 70 HP powerpack.  As soon as we got to camp, I made a 50 mile trip home that evening then another 45 miles the next morning to the shop, got the powerpack, then back to camp with it installed for the next day of fishing.


Now while at camp, I checked the 9.9 out, changed plugs, ran it on the muffs, re-adjusted the carburetor, it looked like a go, yet I knew something was wrong, but we needed it for fishing the next day, so tried another day of fishing.  I got another 4 hours on it before it died for good, with the bottom plug being fouled considerably.   OK, this ended the fishing for that season. 


Tear it Apart :  At the time it was taken out of service and before disassembly, a compression test was taken which showed 108# on the top cylinder and 105# on the bottom.   Wow that was good, but read on.


The standard 50-1 gas/oil mix was used because of the recent rebuild.   Since it had an electric starter, we had no noticeable differences, except harder starting.   The motor was still running this last day when it, at the time it was taken out of service, but the bottom plug was fouled considerably.


Look at the photos below.   The #2 piston pulled about 1 1/4" of the top of the top ring groove, breaking the top ring, but it stayed in place.  It sucked LOTS of piston aluminum chunks back into the intake ports and then into the #1 cylinder.  Miraculously, the #2 cylinder wall was not scored badly where only a good honing job was required to clean it up.  The top cylinder wall also had scores about the same as the #2, apparently from piston pieces being sucked back thru the intake ports  


The block got bulged with a hole about 1/8" discovered on the RH #2 cylinder location just forward of the cylinder liner.  This was cracked by aluminum piston pieces being sucked behind the piston thru the ports, then got wedged between the rod's crank end and poked out as the rod came around close at the base of the cylinder.   A clean up and wire-feed welding job remedied this problem.   However this could have been probably been taken care of with a J-B Weld epoxy repair.


What amazes me is that even with the hole in the block AND the broken ring/piston that this little motor still ran, not good , but it ran.


Here is evidence of the broken piston pieces being imbedded into the head Here the blown  piston, missing the top section of the  lower LH ring groove.   Note, the arrow pointing to the ring that has broken but stayed in place in the groove.


Block Damage :  Shown below was the block damage.


Here on the left, is the hole after being cleaned up in preparation for welding The same hole but viewed from the inside


Reassembly & Why it Blew :  After the repairs to the block were taken care of, the cylinders, re-honed and new piston & rings installed, upon final assembly the real reason for the failure became apparent.  


In the photo below, you will see that the block to reed valve plate gasket is folded over in between the reed valve and stop plate.  This would explain the common thought as to when a piston is damaged like this that it is because of to lean a fuel mixture.  Here the bottom reed could not open enough to allow enough oil rich fuel to lube the piston.  Plus another possible crankcase leak.   It is a wonder that this motor ran so long after things happened and I got away with just the damage that occurred.


Apparently when I replaced these gaskets after the initial rebuild, this motor being the newer series, allowed me to remove the manifold without removing the whole powerhead.  Somehow in the re-assembly this gasket got folded under and it being out of sight underneath, I missed that on the final bolt up.   You can also see where a chunk of the piston was driven against the reed valve, damaged the reed and plate.


Now things are starting to make sense as to why it blew.


Damaged reed valve & plate, showing the displaced gasket


I salvaged a used plate and reed off an earlier motor, changed the rest of the parts and finished the repair job with new gaskets.


All in all, very good fishing but catching was terrible, then with the motor problems, sometimes makes you wonder just why I took up fishing as a pastime.


Now almost 2 years later, it is back in service trolling for fall salmon in an estuary.  It runs very good, trolls all day without missing a beat pushing an 18' aluminum boat that weighs in at near 2800#.  I have now 7 days of fishing with about an average of at least 6 hours each day and I just changed spark plugs.


But as I get older, being able to lift this motor up out of the water when making another run upriver gets a bit hard by the end of the day.  OK, I had been doing odd repair jobs and had stashed enough to go "Whole Hog", and bought a new Yamaha T-8 4 stroke with power tilt.  Now this solved a couple of problems, the tipping it up AND being able to eliminate the 6 gallon mixed gas fuel tank in the motor well.  Life moves on.



Copyright 2007 - 2015  LeeRoy Wisner  All Rights Reserved

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Originated 09-28-2007, Last updated 12-15-2014
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