Seized 4hp Seahorse

[mattjeanes]

I've just bought a 4hp Seahorse on ebay as a restoration project for my 11 year old daughter. Apparantly it ran last year but was not winterized and it is now seized. We have removed the head and soaked the pistons in penetrating oil but still no movement.

What next?

Do we try applying more force to the flywheel?
Is it OK to use a piece of wood and hit the top of the pistons?
Should we try further dismantling?
Is it likely that seized bearings are a problem rather than seized pistons?

 

[Scaaty]

Re: Seized 4hp Seahorse

Breaker bar on the flywheel, just keep back and forth on it, cut down a 2x4 to fit the bore, and GENTLY rap the piston. Don't pound the hell out of it. Just keep at it. Soak the upright piston with PB Blaster, and give it a day or so to soak in..Keep us posted...we can walk ya through it. It will run again. Easy to work on, parts available. Good Luck!

 

[Chinewalker]

Re: Seized 4hp Seahorse

DO NOT torque on the flywheel to break it free! The 4hp models have aluminum rods that can bend, stretch, or even break with excessive pressure from the crankshaft.

The best way to deal with a stuck motor is to completely disassemble it. You didn't mention the year or give a model number so it may have bronze or steel bearings. If there is corrosion in either, you will have major issues down the road, even if you break it free now. Tear it down and inspect it. If the bearings are fine and it's the pistons that are stuck, once it is apart, you can press the pistons out with a wooden dowl and an arbor press. You can clean up the bores with a brake cylinder hone, and if they clean up nicely and are in spec, install new rings and be on your way.

Those little 4s are excellent motors and well worth putting some time and money into to revitalize them...

Have fun! My 12-year old wants to restore his 5.5 Johnson this winter, so I know the feeling...
- Scott

 

[mattjeanes]

Re: Seized 4hp Seahorse

Thanks for the replies. The model number is 49B36D which I think I am right in saying makes it a 1979 model.

In response to the first post I put a bar on and applied a fair bit of torque. Hope it didn't do too much damage! We will disassemble it next.

I can see by the flywheel that the previous owner tried to free it using a hammer as one corner of the starter moulding is bent - looks a bit messy but hopefully no serious harm done.

 

[Silvertip]

Re: Seized 4hp Seahorse

Freeing a seized engine is an exercise in extreme patience. Soak it and wait. Soak it and wait some more. Note that I didn't say "try to rotate the flywheel". Breaker bar on the flywheel on this small engine is also not a good idea unless you want to break ring lands. Sometimes it takes weeks of soaking before you can get even a tiny bit of movement. But thats a good thing. Once you get a little bit of movement, soak it some more and wait. After each waiting period (days to weeks), rotate the flywheel only within the limits of its freedom. This rocking motion distributes the PB Blaster, or whatever you are using, a little bit more with each attempt. You will generally be rewarded with an undamaged engine. Get in a hurry and you run the risk of damaging things.

 

[Scaaty]

Re: Seized 4hp Seahorse

Maybe I didn't come clear with the breaker bar.I didn't suggest try to bend a rod.....I said back and forth. You can't do back and forth with a Ratchet, and a wrench might not fit if the nut is recessed.......
If it froze up from lack of oil, do as Paul sez...rip it apart

 

[iwombat]

Re: Seized 4hp Seahorse

In addition to the soak, a little freezing and heating can help a bit too. Just keep shoving the penetrating oil at it and applying a little pressure to try and get some movement going. If the rings are stuck, it'll be much easier to free them up with the engine assembled and the rods attached to the crank.

 

[iwombat]

Re: Seized 4hp Seahorse

I should put some parameters on that before someone goes and bakes a powerhead in the oven.

Tossing a powerhead in the freezer for a couple of hours is pretty safe. The lube will get pretty thick, so you don't want to move anything too quickly, but it won't hurt anything while you're trying to bust the rings free. The pistons and rings may contract enough to make all the difference.

Heating is another matter. 200-degrees is about the very upper range you'd want to subject a powerhead to, and certainly not for extended periods of time. I keep a propane bbq in the shop for heating parts and get it going to about 175 when I need something good and warm for whatever reason.

Your ultimate combination for freeing the pistons is cold pistons and a warm cylinder block. Generally, you're going to achieve one or the other unless you can get pretty creative.

 

[casi77]

Re: Seized 4hp Seahorse

did you remove the powerhead from the body completely? I would dismantle the whole thing if I was doing it.

I've just bought a 4hp Seahorse on ebay as a restoration project for my 11 year old daughter. Apparantly it ran last year but was not winterized and it is now seized. We have removed the head and soaked the pistons in penetrating oil but still no movement.

What next?

Do we try applying more force to the flywheel?
Is it OK to use a piece of wood and hit the top of the pistons?
Should we try further dismantling?
Is it likely that seized bearings are a problem rather than seized pistons?

 

[joblo33]

Re: Seized 4hp Seahorse

did you remove the powerhead from the body completely? I would dismantle the whole thing if I was doing it.

That also rules out a frozen leg. Maybe even pull the leg first. It's always nice when it turns out that's all that's seized..
Eric

 

[iwombat]

Re: Seized 4hp Seahorse

I guess I was kind of assuming you had the powerhead off. Maybe we should take a step back here and ask what the current state of assembly/disassemply is.

 

[mattjeanes]

Re: Seized 4hp Seahorse

We've now removed and dismantled the powerhead.
The crank needle bearings were quite rusty. The centre ones were the worst and have left some marking on the crank - how much is too much?
Tapped the top of the pistons using a hammer and a piece of wood. One has now moved a little, while the other is still solid. Leaving to soak some more before trying to figure out a way of knocking it back in the other direction without wrecking the con rod.

 

[Chinewalker]

Re: Seized 4hp Seahorse

Hi MattJeanes,
If you have access to a hydraulic or arbor press, you can usually press pistons out with a hardwood dowl. Make sure you press only on the piston, not the rod. Go at it from the crankcase side, not the cylinder head side.
- Scott

 

[mattjeanes]

Re: Seized 4hp Seahorse

Pistons are now out. Looks in need of a rebore.
Next problem is getting hold of parts. I looked on the Bombardier website and my model isn't listed. According to the plate the model # is 49B36D and serial # is B077752. Anybody recognise these?