Disassembly of a stuck Forty Minus SJM

You can talk about almost anything here

Moderators: John@sos, charlesp, Charles uk, RickUK, Petergalileo

User avatar
Stinch
Posts: 11
Joined: Thu Aug 13, 2020 1:21 am
Location: Connecticut

Disassembly of a stuck Forty Minus SJM

Post by Stinch »

Saw this Forty Minus on Facebook Marketplace about three weeks ago but put it off for a while since I recently bought a Century 100. Did I really need another one Seagull since I have two others that don’t run? Decided to bring it home last week anyway. The seller was local and was only about 20 minutes from my house.

20200825_183213 (Medium).jpg
Sorry for sideways pictures. They display properly if you click on them.

20200825_183228 (Medium).jpg
Have to go with what I have.

20200825_183259 (Medium).jpg
The serial number is SJM 50761.


There is an alphanumeric string impressed lightly on the flywheel “R82A80 9/61”. This Seagull appears to be complete and only missing the (plastic?) thrust block. The biggest problem is the motor does not turn over. Took out the spark plug and poured some Kroil inside the cylinder.

Started the disassembly from the bottom up. The two front end cap screws came off with no problem. Removing the end cap revealed an oily interior and nothing poured out like I’d expect. At least it wasn’t dry and rusty so that's good.
20200825_183411 (Medium).jpg
Gearbox looks clean

20200827_173949 (Medium).jpg
So far the gearbox is looking hopeful.
You do not have the required permissions to view the files attached to this post.
Last edited by Stinch on Wed Sep 02, 2020 11:20 am, edited 1 time in total.
Forty Minus - SJM 50761
Forty Plus - FPL 1890 E9
Century 100 - LLS 624 A5
User avatar
Stinch
Posts: 11
Joined: Thu Aug 13, 2020 1:21 am
Location: Connecticut

Re: Disassembly of a stuck Forty Minus SJM

Post by Stinch »

The collar on the propeller shaft does not have a spring pin (as my 1969 Forty Plus) but appears to be solid and peened at both ends. Is this normal for an early 60’s Forty Minus? Is the removal as simple as filing one end of the pin and pushing it out with a punch? Can a spring pin be used or do I have to use another solid pin?

20200831_213121 (Medium).jpg
Propeller shaft collar and pin


Got the drive shaft off the crankshaft and found the pinion turned but it is stiff. Poured some Kroil penetrating fluid into the drive shaft and put it aside to soak. Also removed the silencer tube to get a closer look at the piston rings.

20200828_211318 (Medium).jpg
Not looking good

The biggest challenge now is the frozen piston. Took the time to find a large slotted head bit to fit the cheese head cylinder head screws. Used an acetylene torch to heat each screw head and the cast iron corners in the area of the screw threads. Most broke free but the most difficult was the one near the water exit.

20200829_115034 (Medium).jpg
Got the block hot enough to start a fire


A number of heat cycles and the head finally came off. The water jacket wasn't too bad and cleaned out with a minimal amount of rust. Now I have access to the cylinder walls and the top of the piston. So far so good.

20200829_125424 (Medium).jpg
Cylinder walls have some rust but hopefully will clean up
You do not have the required permissions to view the files attached to this post.
Last edited by Stinch on Wed Sep 02, 2020 11:21 am, edited 2 times in total.
Forty Minus - SJM 50761
Forty Plus - FPL 1890 E9
Century 100 - LLS 624 A5
User avatar
Stinch
Posts: 11
Joined: Thu Aug 13, 2020 1:21 am
Location: Connecticut

Re: Disassembly of a stuck Forty Minus SJM

Post by Stinch »

20200830_184339 (Medium).jpg
I was able to lift the block partially from the crankcase assembly.


The crank turned enough to give enough room to clear the two studs that attach the block to crankcase.

20200830_214907 (Medium).jpg
Even better

20200830_215314 (Medium).jpg
Open crankcase with access to the connecting rod screws

With the lower crankcase half open, I was able to remove the connecting rod screws. Made sure the connecting rod cap spacers were put back into their original location.


Now I have the block free and can work the piston problem without risking damage to the crankshaft. Soaking the lower cylinder in Evapo-Rust to clean out the surface rust as this will be (hopefully) the piston exit. Doubt this will be the last soak in this area. Next I'll do some scraping and more soaking.

20200831_194125 (Medium).jpg
Evapo-Rust soak.


I’m continuing to review various options to get the piston out including the use of a grease nipple on the cylinder head to break the piston free. More to come.
You do not have the required permissions to view the files attached to this post.
Last edited by Stinch on Wed Sep 02, 2020 11:21 am, edited 1 time in total.
Forty Minus - SJM 50761
Forty Plus - FPL 1890 E9
Century 100 - LLS 624 A5
User avatar
Charles uk
Posts: 4784
Joined: Wed Feb 27, 2008 4:38 pm
Location: Maidenhead Berks UK

Re: Disassembly of a stuck Forty Minus SMJ

Post by Charles uk »

Stinch, what do you think was causing the head screws to stick in place so tight?

Thanks for an informative thread that doesn't involve the use of a big hammer & an electric drill!
Make it idiot proof and someone will make a better idiot.
User avatar
Collector Inspector
Posts: 4037
Joined: Sun Jun 29, 2008 4:32 am
Location: Perth Western Australia
Contact:

Re: Disassembly of a stuck Forty Minus SMJ

Post by Collector Inspector »

Gently gently as you are obviously doing.

The piston will move just keep doing what you are doing.

Yeh good progress.

BnC
A chicken is one egg's way of becoming others
User avatar
Stinch
Posts: 11
Joined: Thu Aug 13, 2020 1:21 am
Location: Connecticut

Re: Disassembly of a stuck Forty Minus SJM

Post by Stinch »

Charles uk wrote: Tue Sep 01, 2020 8:36 am Stinch, what do you think was causing the head screws to stick in place so tight?

Thanks for an informative thread that doesn't involve the use of a big hammer & an electric drill!
Seagull made some fine little outboards but I’m not sure what they were thinking with the design of the recessed cheese cylinder head screws. Guess they were not thinking of the restorer 60 years later. The bottom of the cylinder head screw is exposed to the water jacket. As the years go by the threads also get locked in by the cast iron. The recess makes it impossible to grab the top of the screw with locking pliers to assist if need be. The slotted screw doesn’t provide the best grip for a screwdriver either. It was very important to have a screw bit that fit the slot tightly. If things had gone wrong and the slotted head rounded out, I would have welded a washer to the top of the screw and a nut on the washer after that. Fortunately patience paid off.
Last edited by Stinch on Wed Sep 02, 2020 11:21 am, edited 1 time in total.
Forty Minus - SJM 50761
Forty Plus - FPL 1890 E9
Century 100 - LLS 624 A5
User avatar
Charles uk
Posts: 4784
Joined: Wed Feb 27, 2008 4:38 pm
Location: Maidenhead Berks UK

Re: Disassembly of a stuck Forty Minus SMJ

Post by Charles uk »

All the really stuck head bolts, I've had problems with seem to be locked in place by aluminium oxide, that horrible white powder that seem to hold the much tighter than Loctite, in the head itself not in the threaded part of the cast iron cylinder.

After I've cleaned the holes in the head, I now always put them in place covered in RTV silicon, no room for water ingress & they come out without any Drama!
Make it idiot proof and someone will make a better idiot.
User avatar
Stinch
Posts: 11
Joined: Thu Aug 13, 2020 1:21 am
Location: Connecticut

Re: Disassembly of a stuck Forty Minus SJM

Post by Stinch »

The Evapo-Rust soak worked really good. After 24 hours the cylinder walls below the piston were smooth and I only wiped the inside with a cloth. The dark spots don't feel like pits. After a water rinse, I dried as much as I could with a shop towel then sprayed it with WD-40.
20200902_181047 (Medium).jpg
Lower area of the cylinder walls after the rust has been removed.
You do not have the required permissions to view the files attached to this post.
Forty Minus - SJM 50761
Forty Plus - FPL 1890 E9
Century 100 - LLS 624 A5
User avatar
Collector Inspector
Posts: 4037
Joined: Sun Jun 29, 2008 4:32 am
Location: Perth Western Australia
Contact:

Re: Disassembly of a stuck Forty Minus SJM

Post by Collector Inspector »

Good progress.

Next find a lump of stout wood that fits the bore nicely while it contacts the piston crown as much as possible of course.

Warm up the barrel and try drifting the piston out with a decent sized hammer or similar (you can also use a block of wood instead of a hammer...less shock for the rings but supplies some force).

Not moving?

More soaking and try again later.

Rings are cheap as when you finally get the piston out, they will be still stuck in the piston. If you break one no biggy. They can be Uber Stuck.

Good fun aye?

BnC
A chicken is one egg's way of becoming others
User avatar
Charles uk
Posts: 4784
Joined: Wed Feb 27, 2008 4:38 pm
Location: Maidenhead Berks UK

Re: Disassembly of a stuck Forty Minus SJM

Post by Charles uk »

Here in the UK aluminium scaffold tube is 50mm OD, I have an 8 inch length that I turned down 4 inches of it to 44.8 mm OD, all you have to check is does the big end of the con rod fit up the tube, then you can drive the stuck piston up the bore towards the area with the most wear, & use plenty of lube.

Less chance of piston damage, sometimes ice in the piston helps if you warm the cylinder, as aluminium expands more than cast iron.

Sometimes an hour in the ultrasonic cleaner will free the rings.
Make it idiot proof and someone will make a better idiot.
User avatar
Collector Inspector
Posts: 4037
Joined: Sun Jun 29, 2008 4:32 am
Location: Perth Western Australia
Contact:

Re: Disassembly of a stuck Forty Minus SJM

Post by Collector Inspector »

Good idea that Charles (the tube).

And you would not believe what I have in my (large) ultrasonic cleaner at the moment. :wink:

BnC
A chicken is one egg's way of becoming others
User avatar
Stinch
Posts: 11
Joined: Thu Aug 13, 2020 1:21 am
Location: Connecticut

Re: Disassembly of a stuck Forty Minus SJM

Post by Stinch »

A few days ago I poured some kerosene in the block and used a section of a shop towel as a wick. Let it burn for about 30 minutes.

20200904_113046 (Medium).jpg

After it burned off, took some ice and dropped it into the inverted assembly to cool the piston. Turned it back up and used a hammer with wood block on the piston top a few times. Nothing moved. Did a second cycle of this technique and it still didn't move. The wood supports under the block began to break up so I stopped.

Started thinking about a 2 ton arbor press I had. Turns out, the ram just fits inside the cylinder. I tried putting pressure on the piston top but it still didn't move. Don't feel comfortable knowing most of the force is only on the offset/high part of the piston.

20200905_133238 (Medium).jpg

I did notice a little penetrating fluid was leaking past the rings and coming out the exhaust port. It takes overnight for this happen. Feel like I'm getting somewhere.

Now I'm soaking the block and piston assembly in 50/50 acetone and ATF and see what that does over the next two weeks.

20200907_191321 (Medium).jpg

After this soaking, I'll give the arbor press another try and not force things. If this doesn't work, I'll give the grease fitting technique a try. I'll reinstall the cylinder head with original steel gasket. Install a grease fitting and use the pressure from the grease gun to move the piston. I don't expect it to go far as it looks like the piston top is near the exhaust port.

If all else fails, I'll take it to a local machine shop and have them make the tube tool that Charles suggested. Sounds like the best way to spread the forces over a large area under the piston edge and still keep the piston in alignment.
You do not have the required permissions to view the files attached to this post.
Forty Minus - SJM 50761
Forty Plus - FPL 1890 E9
Century 100 - LLS 624 A5
User avatar
Collector Inspector
Posts: 4037
Joined: Sun Jun 29, 2008 4:32 am
Location: Perth Western Australia
Contact:

Re: Disassembly of a stuck Forty Minus SJM

Post by Collector Inspector »

Stuck as obviously.

Keep on at it.

BnC
A chicken is one egg's way of becoming others
User avatar
Oyster 49
Posts: 3176
Joined: Tue Oct 26, 2010 6:55 pm
Location: Derbyshire, UK

Re: Disassembly of a stuck Forty Minus SJM

Post by Oyster 49 »

Keep at it, hot/cold cycling can help. Can you get it hot and put it in the press again?
andrew
Site Admin
Posts: 72
Joined: Wed May 24, 2017 5:37 pm
Location: Greenwich, USA

Re: Disassembly of a stuck Forty Minus SJM

Post by andrew »

Any movement in the piston? Wondering if you ever tried the grease nipple approach. Cheers!
Post Reply