engine is seized up

Steve Dion · Feb 23, 2012

Rick:

I would pull the head and see what is going on first. Do you still have a QM engine?

kloudie1 · Feb 23, 2012

Decompression levers ON so it can turn? Turning it with the crank and chain sprocket? Chain free? I suggest pulling the decomp levers and trying to rotate by rocking back and forth at the front pulley before doing anything else .. did it turn before? Lotsa questions..not trying to grill ya, just need more info..

Jim Legere · Feb 23, 2012

Rick is this a new discovery or do you think it has been this way since you purchased the boat? If it is recent, try putting some penetrating solvent in the cylinders to see if you can free it up. Steve's suggestion of pulling off the cylinder head is a good one too. For the price of a head gasket at least you will be able to see if there is water damage etc. Any engine can be rebuilt but if you are not mechanically inclined and do not do a lot of the work yourself, it is going to cost you possibly more than a new engine. I had a seized Volvo Penta on my last boat that I was able to free up and rebuild. Parts cost me about a 1/3 of the cost of a new engine and I did all the work, except machining myself. If you end up scrapping the old Yanmar, keep in mind that lots of us here in Cherubini Hunter land would probably like to get a crack at any good used parts!

Johnb · Feb 23, 2012

http://forums.hunter.sailboatowners.com/showthread.php?p=320991&highlight=siezed engine

See the above for a previous discussion

Benny17441 · Feb 23, 2012

The simplest indicator of the condition of the engine may be the oil in the crankcase. Check the color and viscocity. The oil should be black, if it is gray that would be evidenced that water has entered the cylinders and emulsified with the oil. Absence of oil or presence of a goo may not be good either. It would help if you knew the history of the engine. You may also remove the valve cover and perhaps judge the condition of the engine as relative to what you find with the valve train. It is also important to notice if the engine turns a little bit or whether is frozen solid. These are merely preliminary indicators of what may lay ahead. The next step would be what others have advised in removing the cylinder head to take a peek into the engine and the actual cause of the seizure. If the cylinders walls are heavily damaged by rust with the piston rings fused to them the engine may be beyond repair but sometimes the rings just get stuck for lack of use and could be freed by soaking in oil and slowly trying to turn the engine. Evidence of a broken piston or connecting rod may require a complete teardown and assessment of the cylinder block, cranckshaft and other parts to determine the viability of a rebuild. If the engine can be rebuild and you could do the job yourself that would be your best option. As a 2nd option you may consider looking for a used engine and rebuilding that one in case yours cannot be fixed. Last option would be to repower with a new engine as the cost will likely exceed your total investment in the boat. There is one last option that you have not mentioned and that is to sail engine-less. This last one may not be practical for most people who just want to go out there and come back within a certain time frame. Hope the engine salvageable.

Dan Hill · Feb 25, 2012

If you need to get to the crank to pull pistons and rods you will need to pull the motor. Removal of the pan in the vessal is most likely impossible IMHO.

AtlanticAl · Feb 25, 2012

Before you take the thing to pieces, try turning the engine in reverse. A thing that can happen, is a push rod jumps out, then gets stuck stopping the rocker from going down, and holding the valve open, and the piston comes hard against the valve, and the engine seems as if its seized. If it is siezed, pistons siezing on a four stroke engine, are not that common, its much more common, for a big end bearing to sieze, or a main bearing, but usually the big end siezes while its running, and the con rods break, and burst a hole in the engine casing. If it turns backwards, take the rocker covers off, and see what is going on. If its any kind of other siezed, its pretty much a re-build.

Jim Legere · Feb 25, 2012

AtlanticAl said:
If it is siezed, pistons siezing on a four stroke engine, are not that common, its much more common, for a big end bearing to sieze, or a main bearing, but usually the big end siezes while its running, and the con rods break, and burst a hole in the engine casing. If it turns backwards, take the rocker covers off, and see what is going on. If its any kind of other siezed, its pretty much a re-build.

I would say, based on several engine I have looked at, that piston seizing is VERY common on marine engines. It usually occurs when water enters the engine through the exhaust system. This can hapen a number of ways - wave action, partial sinking, cooling water backing up due to blockage in the exhaust, etc. Given that Rick's boat came from Florida and was hurricane damaged, I think it is possible salt water got in the engine. The fastest way to diagnose the problem is to pull the cylinder head. This will also allow inspection of the pushrods, valve rockers, etc. Let us know what you find Rick.

AtlanticAl · Feb 25, 2012

Jim Legere said:
I would say, based on several engine I have looked at, that piston seizing is VERY common on marine engines. It usually occurs when water enters the engine through the exhaust system. This can hapen a number of ways - wave action, partial sinking, cooling water backing up due to blockage in the exhaust, etc. Given that Rick's boat came from Florida and was hurricane damaged, I think it is possible salt water got in the engine. The fastest way to diagnose the problem is to pull the cylinder head. This will also allow inspection of the pushrods, valve rockers, etc. Let us know what you find Rick.

You are very correct in what you say, but what you find, when the engine fills up with water, which is very common, when the exhaust sucks the water up from the sea, when you sail in bad weather, and your water trap dips bellow the level of the water outside, and you dont have a vent in the water trap, then with the engine full of water, you try to start it, water cant be compressed, so you slightly bend the push rods, the engine may run once drained for a little while, but with the initial damage to the push rods, they eventually buckle, and jump out of place. The pushrods bend because they cant force the valves open, against the pressure of water in the cylinders. Pistons can sieze, but, that will be the very last thing you find out, as you will have the heads off, and the crank off, before you find out that the piston is siezed, unless of course, you somehow get it moving, and even if you do, you would really want to take the pistons out, and re hone the block, and replace the piston rings.

Jim Legere · Feb 25, 2012

Once you have the head off, if you still can't bar the engine over, either pistons are frozen in the cylinders or (less likely) a bearing is seized. With the head off, any water damage will be evident. I sent you a PM Rick.

Redbeard33 · Mar 1, 2012

not to discourage, but those pushrods look quite rusty. Proceed but be skeptical of what lies out of sight

Bill Roosa · Mar 2, 2012

Along with the pushrods the general exterior looks like it has seen a lot of salt water action over the years. May not be anything as salt water on the outside is pretty much a given on marine engines but it is an indicator of previous maintenance schedules.
The inside does look like just oil is getting to the head with no glop emulsified water-oil deposits. The fact that you are getting oil to the valve train but the push rods are rusted may not be an issue though. If memory serves the tappet does not have an oil passage and so the push rod does not get "pressure" oiled, it only get splashes or dripping from the valve rocker journals. Not a crisis but not what you would like to see either. I'm thinking the oil pressure has been low for some time....... which would lead me to suspect a lack of oil in other places as well..... like the rings or (somewhat less likely as they have a dedicated oil passage) the crank and cam journals.
Pretty much have to continue in any case, keep the pics coming so we can help.

redhead78 · Mar 2, 2012

Do u know how many hours are on the engine. AS far as weight, is tranny still attached?? If u remove the head and trans u are probably still looking at 3-350lbs.. Red