Yanmar 3gm 30 engine seized

Jim26m · May 13, 2019

Good! You should never run the starter on a seized engine. You really shouldn't have used the cheater bar on it. If a valve or valves were stuck open, you could have turned a quick cleanup into a total teardown and replacement of several parts. Bent valves, connecting rods, broken pistons, are all possible issues depending on how long your cheater is and how much Conan you can exert.

Paper towels just filtered the dirt and bugs out of the moisture as it went in...

I'll let someone familiar with that specific engine tell you what you're in for when pulling the injector pump assembly off of the front end, but if you have the shop manual, it should tell you. I just took a quick look at the parts catalog to get the general layout. I only suggest removing the pump assembly to rule out the possibility that it is seized and the cause of your problem. I don't think that is the case, but I would be pulling parts off anyway if it were mine to get it ready for rebuild.

As has been suggested several times above, pulling the head will tell you if its rust in the cylinders. Maybe that's more in your comfort zone - so just pull the head in lieu of the pump assembly if you can't get comfortable. Sounds like you had settled on that anyway. It will be lighter to pull with the head off anyway. Here's a video of what you're getting into

Take lots of photos and videos as you go to help you remember what you did. Baggies and label your parts and fasteners as you go.

That block is going to have to come out of the boat in all likelihood (sorry). It's probably going to a machine shop or rebuilder depending on your capabilities and tools. Best case, you will have to pull one piston so you can hone the rusted cylinder (if it's only one). I wouldn't think you could do that without pulling the bottom end (pan, crank,etc).

You are about to get into real engine work, so if you're not up to it, pull it out as a single piece and take it to a rebuilder. In my neck of the woods, they charge a lot for pulling and re-installing - which sounds like stuff you might handle. This will save you a chunk of change.

You might want to call a rebuilder and get a ballpark rebuild cost. Then you can compare that to a new shortblock (or longblock - depending on damage and availability). Might make sense to just replace the block (and maybe head), rather than rebuilding yours. There is a chance that yours may require more cost to rebuild than a replacement. A replacement engine might be within your means (we haven't discussed budget). If so, that might give you more peace of mind on the water. Check with https://www.dieselenginetrader.com/engines/Yanmar/3GM30F/16578 for reman engine source (schooner bay marine). Looks like $5k+ for a reman...

Sorry I can't give you a silver bullet. Until you get it apart and determine what you've got, we're all just guessing.

Good luck and keep the posts coming. We're rooting for you.

Michael Davis · May 14, 2019

If you're willing to spend the time and have some tools:- they wanted $5000.00 to rebuild my Universal 5411. In the end I down loaded the shop manual, took the engine home and rebuilt it myself for about $500.00. First engine I've ever done, pretty scary to start but they are pretty simple.

Hayden Watson · May 14, 2019

I would suggest that you stop trying to force the engine to rotate. There is obviously something that is rusted or bent and forcing it will just cause more damage.

Jim26m · May 14, 2019

Nope - pull the head - the suspense is killing us.
If your engine is just tired, cylinder bores within spec, crank and cam still within spec, you can do a parts swap rebuild and come out with a good result. An engine exposed to the environment described, and seized for the stated length of time, may require another level of attention. You can still do it, with the shop manuals, tools, patience, and grit. You may have to have a machine shop do some work on the block and/or head. Not a big deal, but something to consider. I've only done one where I had to beat a piston out of the bore. Boat was partially submerged in brackish water. Engine had water in it for weeks, but water only appeared to have made it into one cylinder. It took a new piston. I was able to hone the cylinder to roughly satisfactory condition (owner was on a tight budget and a friend - machine shop was out of the picture). It wasn't right, but it ran ok.
If it's just stuck with surface rust, it may hone out and all may be well. I hope that's the case.

See post above. You may wind up destroying usable parts if you keep trying to force crank rotation.

garymalmgren · May 15, 2019

HH
Do not fear. Fear is the enemy.
You have a manual, don't you.
Follow the steps.
My suggestion is to get yourself a handful of ziploc bags.
As you remove each part of the head assembly (rocker cover, rocker arms. push rods, head bolts and then head)
Mark (with masking tape) each bolt and part and put in the bags. Take photos too. This will make reassembly easy.
With the head removed there should no resistance to rotation except binding of the pistons to the cylinder walls.
Load up the piston tops with your favorite deseizer, Have some one put some weight on the jimmy bar on the crankshaft nut and lay into the piston tops with a hefty hammer and a lump of wood.
Even if you get the engine to rotate you will still have to deal with the corrosion or whatever the cause of the seizure is, so you will then need to follow Michael Davis's line of reasoning.
Most of the rebuild you can do yourself (with advice from here) and other bits , like a head rebuild you will need to leave to specialist.
Come back to us when you have the head off and really know what is happening inside the engine.

Gary

Hayden Watson · May 15, 2019

Once you get the head off, I suspect that you will find rust on the inside of the bore. do not try to put the pistons up with the rust present. get a cylinder hone and give it a light honing wot remove the surface rust. flush the cylinder with brake fluid and wipe with oil before removing.

jviss · Jul 27, 2019

Now that the head is off, can you turn the crank back and forth a bit and see if any of the pistons move?

I think you're in for a full tear-down; might have to get that block onto a press and try gently pressing the pistons out (after removing the crankshaft, of course).

Jim26m · Jul 27, 2019

Wipe the cylinders out with a rag and stick your finger in the bore. With your fingernail pointed upward, drag it toward the top of the cylinder. Is there a ridge in the bore that you can catch your fingernail on? It will be near the top, about 1/4" in if you have one.

I can't tell much from the photo, because of all of the liquid in the bore, but are the cylinder walls corroded?

As @jviss asks above, can you move the crank at all? If so, try to expose cylinder wall that is behind piston, and get a pic of that.

If you can get a good shot of the cylinder wall, and report on if you have a ridge, and how much ridge there is, that would be helpful.

At this point, if the cylinders are corroded, you need to assess whether you can pull the pan and crank in place. If not, the block needs to come out where you can work on it. If you can pull the crank in place, and the cylinders just have a light surface issue that you can clean up with honing, you might get away with doing it in place. Looks kind of tight in the photo, though, and it is going to be messy. It would be much easier to do it out of the boat (other than the obvious issue of getting it out and back in).

Jim26m · Jul 27, 2019

Since you found a ridge, you will likely need to remove it before you can get the pistons out. This video gives you an idea of what that's about. These tools vary a bit in design. Mine is slightly different, but this is the basic overview.

Due to the amount of cylinder wall corrosion you appear to have, I think you need to pull the bottom end, i.e. oil pan, crankshaft, and get the pistons free to move independently. Trying to free it up with the crank connected is going to make it, orders of magnitude, more difficult. If you are lucky, they'll only be stuck on the top ring or two, and you'll be able to force them down into the bore - one at a time. This will only be possible after you pull the crank out. Once you drive the pistons down a bit, you can do exactly what @Hayden Watson recommends and clean the bore out, remove the ridge, and pop the piston out. My hope is, there wasn't a lot of moisture in the bottom end, and that the pistons will move down fairly easily. If so, you will still be able to disassemble it without breaking anything.

Be careful driving the pistons down, once they start moving. Use a large block of wood that covers as much of the piston as possible. Rocking it a bit from side to side, as suggested above might help break it loose, but be careful doing this. The piston is designed not to allow much rocking in the bore. What you're trying to do is start a small portion moving at a time rather than having to force it all to move at once. So, for this, concentrate light, sharp blows around the perimeter alternating across the diameter. Again, use wood or similar material. Don't strike the piston with a metal hammer.

garymalmgren · Jul 27, 2019

im going to let it soak good
Good.
Go slow and don't skip any of the steps.
You can't really decide the next move until you get the engine to rotate and can check the condition of the cylinder bores.

Just to give you an image of what lies ahead.
There are basically two types of piston seizure
1. Rings rusted/seized to bore.
This is caused by moisture (either water from an internal leak or condensation) causing rust between the rings and bore and thereby seizing the piston. it is only over a very small area and once freed can be ok. This is the easiest problem to deal with and can range from easy fix to big headache.
To free the seizure you are on the right track of soaking.
If it is pooling on top of some pistons , they could be the culprit but that is not guaranteed
Once soaked you need to put tension on the crankshaft and whack the top of the pistons as jim26 suggests.
Don't be afraid of causing damage. Those pistons are subjected to intense stress every time the engine fires.
Once you break the seal she should rotate relatively freely.
Take each piston to the bottom of its stroke and inspect the bores.
Come back to us with photos at that stage.
The second type of piston to bore seizure is something you don't want to know about at this stage. LOL.

Gary

leo310 · Jul 27, 2019

At this point in time you should just pull the block and work on it at home. The reason why is you may as well do a complete rebuild ie new bearings and other parts plus you will have more room to pull the crank shaft and see what the bottom of the pistons look like as you may have a bent rod or worst broken that has jammed causing the rotation problem. Just remember doing your own rebuild will save money and you'll know it was done by the book. At the same time look at the tranny.

Yanmar 3gm 30 engine seized

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