starcraftkid
Petty Officer 1st Class
- Joined
- Jul 5, 2010
- Messages
- 231
I picked up a clean looking 1983 35hp Johnson a few months ago, it came to me attached to the back of a junk 15ft trihull that I promptly turned into mulch.
The story I got was that it was their dad's boat and he had taken ill and died in 2017, but they remember him using it the prior season over in PA.
The boat was a bad bass boat conversion of sorts where someone had added 400lbs of plywood and carpet to make a deck boat with hatches out of it. Although it was stored under a carport all the wood was soft and rotted and the hull waterlogged.
I was mainly after it for spare parts and it was 'free' with a two year old trailer for $200.
I let the motor soak for a few month but no change, it was locked up tight.
I pulled it apart, tearing it down to a bare block and two stuck pistons.
The rest of the motor was in super shape, almost no signs of wear or heat damage.
The first thing I found was some rust on bottom of both cylinders, one piston was at tdc, the other nearly at the bottom. With the crank out, and lots of oil I was able to tap the top cylinder out of the bore but it was tight. The both rings were stuck at the bottom of the piston.
The bottom cylinder wouldn't move, so I soaked the block in hot atf at about 140 degrees. After a few hours I was able to tap it down in the bore slightly where I could clean up some rust at the top, after some careful finessing with a large hammer and block of wood I was able to get the piston out. Both rings were firmly stuck. I washed off the block, ran a ball hone through both bores and the cylinders look great, there's no pitting, scoring, or transfer.
After soaking both pistons in a hot ultrasound cleaner the rings released, but the second ring on the lower cylinder came out in pieces. The others all came out perfect.
With the pistons cleaned up, I popped out the wrist pins and found the lower wrist pin badly pitted from rust, but the rod was untouched.
With the pistons bare and clean, and the block now run through two cycles in the spray washer, I figured I'd loosely assemble the block till I get a few new parts. (It also needs a lower crank bearing which was rusted and rough).
I went to drop the pistons in the bore and was having trouble getting them to go. I then turned them over and they drop right in but stop 1" from the bottom of the skirt.
In checking the piston skirts, I find both piston skirts exactly .014" larger than the area behind the bottom ring.
Neigther piston has so much as a scratch on it and both cylinders were honed slighty to clean up any rust or rough spots and nothing is visible to the naked eye and both cylinders measure 3.00" and are round with no taper. both pistons measure 3.014" at the base of the skirt but 2.94" at forward 1" in a rapid but smooth taper. (There's no bulge or flare that can be seen or felt).
I've been building motors for 40 years, mostly big diesels, but have never seen piston skirts expand?
This was a motor that was on a boat being used. It shows no signs of being blown up or overheated, the water pump impeller was in good shape, and its super clean. There's zero cylinder wear and zero bearing wear or tracking that normally shows with age or use.
The area of the cylinders where the skirts were sitting was clean in both bores, the only rust showing was at and above the rings and a little bit on the top if the crank counterweights. The bearings were clean and well lubed still soaked in oil.
Two things that I don't get is that neither piston skirt is scored or scratched, even from driving them out but I did have both bores completely soaked in atf while doing it and had removed the rust at the top before hand.
It took moderate force to remove the top piston, but the lower piston tool me using 5 pound deadblow hammer and a piece of 2x3 wood. Once it moved, dowward at first, it came out fairly easily but not freely.
While I'd like to put this back together again, its no a priority and was a free motor that gives me lots of spare parts but I just can't figure out how two pistons that I just tapped out of a block seemingly grew too large to go back in.
Any ideas?
The story I got was that it was their dad's boat and he had taken ill and died in 2017, but they remember him using it the prior season over in PA.
The boat was a bad bass boat conversion of sorts where someone had added 400lbs of plywood and carpet to make a deck boat with hatches out of it. Although it was stored under a carport all the wood was soft and rotted and the hull waterlogged.
I was mainly after it for spare parts and it was 'free' with a two year old trailer for $200.
I let the motor soak for a few month but no change, it was locked up tight.
I pulled it apart, tearing it down to a bare block and two stuck pistons.
The rest of the motor was in super shape, almost no signs of wear or heat damage.
The first thing I found was some rust on bottom of both cylinders, one piston was at tdc, the other nearly at the bottom. With the crank out, and lots of oil I was able to tap the top cylinder out of the bore but it was tight. The both rings were stuck at the bottom of the piston.
The bottom cylinder wouldn't move, so I soaked the block in hot atf at about 140 degrees. After a few hours I was able to tap it down in the bore slightly where I could clean up some rust at the top, after some careful finessing with a large hammer and block of wood I was able to get the piston out. Both rings were firmly stuck. I washed off the block, ran a ball hone through both bores and the cylinders look great, there's no pitting, scoring, or transfer.
After soaking both pistons in a hot ultrasound cleaner the rings released, but the second ring on the lower cylinder came out in pieces. The others all came out perfect.
With the pistons cleaned up, I popped out the wrist pins and found the lower wrist pin badly pitted from rust, but the rod was untouched.
With the pistons bare and clean, and the block now run through two cycles in the spray washer, I figured I'd loosely assemble the block till I get a few new parts. (It also needs a lower crank bearing which was rusted and rough).
I went to drop the pistons in the bore and was having trouble getting them to go. I then turned them over and they drop right in but stop 1" from the bottom of the skirt.
In checking the piston skirts, I find both piston skirts exactly .014" larger than the area behind the bottom ring.
Neigther piston has so much as a scratch on it and both cylinders were honed slighty to clean up any rust or rough spots and nothing is visible to the naked eye and both cylinders measure 3.00" and are round with no taper. both pistons measure 3.014" at the base of the skirt but 2.94" at forward 1" in a rapid but smooth taper. (There's no bulge or flare that can be seen or felt).
I've been building motors for 40 years, mostly big diesels, but have never seen piston skirts expand?
This was a motor that was on a boat being used. It shows no signs of being blown up or overheated, the water pump impeller was in good shape, and its super clean. There's zero cylinder wear and zero bearing wear or tracking that normally shows with age or use.
The area of the cylinders where the skirts were sitting was clean in both bores, the only rust showing was at and above the rings and a little bit on the top if the crank counterweights. The bearings were clean and well lubed still soaked in oil.
Two things that I don't get is that neither piston skirt is scored or scratched, even from driving them out but I did have both bores completely soaked in atf while doing it and had removed the rust at the top before hand.
It took moderate force to remove the top piston, but the lower piston tool me using 5 pound deadblow hammer and a piece of 2x3 wood. Once it moved, dowward at first, it came out fairly easily but not freely.
While I'd like to put this back together again, its no a priority and was a free motor that gives me lots of spare parts but I just can't figure out how two pistons that I just tapped out of a block seemingly grew too large to go back in.
Any ideas?
