Seized 20hp Mariner

[clc48301]

Hello
I'm new to the boating world, and I just bought a 85 Sylvan Supper Snapper off of Craigslist. It came with a seized 20 hp Mariner. The guy I bought it from said it seized up while running. When I tried to pull start, and got about half a pull then it stopped. Now its stuck pretty much at the beginning of the pull. I'm looking for a little guidance on fixing it if possible. Any thoughts? I've read good things about a product called engine release. Has anyone tried this?

Thanks

 

[Laddies]

Re: Seized 20hp Mariner

Turn the flywheel backwards without using the rope start, then try to turn it again if it stops about the same place you probably have a rod out. That can be checked by removing the carb and reed block.

 

[mark abby]

Re: Seized 20hp Mariner

i am not, by far an expert, but my 150 seized on me. when i spoke with a mechanic at a mercury dealer he said i "dry seized" the motor.

i went home and removed the plugs and found the fly wheel could turn about a 1/4". if the motor was seized, i figured it should not move at all. i put a popcycle stick in each cylinder and rotated the fly wheel back and forth and i could feel the pistons moving...which told me that was a good sign!

i then removed the lower unit and again tried to move the flywheel...it moved all the way! the problem was a seized bearing on the drive shaft.

 

[Faztbullet]

Re: Seized 20hp Mariner

What year 20hp ? The early models was a chrome bore and if seized the block is usually junk...

 

[clc48301]

Re: Seized 20hp Mariner

Thanks for your posts.

The motor is a 1984, remote drive, electric start with a long shaft. The serial number 6536553.

I've put the motor into neutral and the prop spins freely. I've taken the cover off and the fly wheel spins. But it reaches a point where it stops, and if you spin it around in the other direction it stops roughly in the same place. Not sure what this means, but once it warms up a little more I plan on dropping the lower end, and hope the bind follows the gear foot.

My next questions is can I put a 1991 25hp Mercury outboard on the boat and reuse the controls and cables? There is a motor on craigslist in my budget range, but I didn't plan on buying new controls with the budget.

 

[mark abby]

Re: Seized 20hp Mariner

the prop will spin regardless.

remove any spark plugs.

drop the lower unit, then try to turn the fly wheel. if it still binds, your problem is in the motor, if the fly wheel turns, the problem is in the lower unit.

 

[clc48301]

Re: Seized 20hp Mariner

I dropped the lower end today. I had some troubles figuring out how to disconnect the shifter. The fly wheel hits a point where its stuck. Starting to think i have a stuck valve. This weekend i will remove the recoiler snd starter, hopefully the bind is there.

If the bind is in the power head is it even worth trying to fix?

Thanks

 

[quicktach]

Re: Seized 20hp Mariner

Do you have the skills and knowledge to do work on a power head? Do you have access to a manual to read about what is involved in a tear down? Sounds like you could have a con rod problem. What is your own time worth to you?

 

[minuteman62-64]

Re: Seized 20hp Mariner

Starting to think i have a stuck valve.

That's a 2-stroke. The only valves are the reed valves on the intake - I don't see how they can be a factor in this.

I don't know what your situation is w/regards to available time, but, even if it's junk doing some disassembly might be a great learning experience that would pay dividends down the road.