Mercury Skirt Problem

Have always done my own maintenance on my XR4. For example: winterization, replaced things like reeds, switch boxes, trigger and stator, rebuild fuel pump and carbs, and have done regular LU water pump replaces.

Have never done any internal motor work (yet) though.

I see this 1999 Mercury EFI for sale. Sounds like it would be a good engine to pick up. I can put my XR4 on another boat I have, so no waste there.

The only info I have on this 1999 EFI is that there is a “cylinder skirt” problem stopping it “from turning”...

First of all I think the skirt is the bottom on the piston below the rings, not on the cylinder, correct?
Also, here is a start of my questions for the owner:

1) How would they know that was the problem without opening up the engine?

2) What was the case of the failure?

Aside from this, if it is just a piston failure, is there a good chance the cylinder is not affected and replacing the piston will take care of it? Any other questions I should ask?

Any input is welcome.

More than likely stuck a piston, meaning piston grew faster/more than cylinder and caused piston to seize to cylinder. Usually caused by overtemp, cold sieze(not allowing engine to warm up and allow slower expanding cylinder to expand before putting it under load making piston expansion to be quicker than cylinder),lack of lubrication, lean mixture, and if top of piston damaged excessive timing. Usually cylinder wall will be scuffed badly and aluminum stuck to walls. Will most likely need to be bored or sleeve replaced depending on extent of damage. Also inspect rods, bearings, and crank journals thoroughly for any damage. The fact it won't turn over is a good indication at least the rod stayed in tact

Good info. Is boring/sleeving a job that can be done by just removing one piston or does the whole block have to be freed up?

The whole thing needs to come down either way. If bored there will be metal shavings and if sleeved block will have to be heated in oven and not good for a lot of components. Pull the heads first and see what's going on. For a quick reference you can pull the spark plugs and more than likely will be able to tell which cylinder is effected by looking at the plugs if they won't allow pulling the heads.

Guess I am not surprised. That makes sense; but I was hoping it would be less work.

By any chance are the EFI's more susceptible to that problem? My XR4 is 30 years old now and has never had that issue (and compression is still even).

A dirty injector or one that is sticking from old varnished fuel can cause one cylinder to lean out. If ya find it stuck a piston, need to get injectors cleaned and flow tested. Replace t-stats, water pump, and inspect poppet thoroughly . Inspect everything closely until able to determine what caused it.

That all makes sense to me. If the plugs are pulled, what would a stuck cylinder look like through that little hole?

The spark plug itself will look grey in color or have aluminum stuck to it.

Thanks, that gives me a lot to go on.

As it turns out, for now anyway, I did pick up a 1993-94 150 (2L) for a really cheap price. Owner said it did run OK before it was stored 8 years ago. This was still taking a risk as it was not possible to get a compression test on it first. Looking at each cylinder and spark plug I see no aluminum coloring; but the crank is still entirely locked up. I believe it is from rust not being stored correctly. If some penetrating oil doesn't work I may have to part it out. A project for sure.

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Originally Posted by Glastron1987

As it turns out, for now anyway, I did pick up a 1993-94 150 (2L) for a really cheap price. Owner said it did run OK before it was stored 8 years ago. This was still taking a risk as it was not possible to get a compression test on it first. Looking at each cylinder and spark plug I see no aluminum coloring; but the crank is still entirely locked up. I believe it is from rust not being stored correctly. If some penetrating oil doesn't work I may have to part it out. A project for sure.

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if its locked up then most likely the bearings on the crank are toast. Best to tear it down and find out why its locked up

pull gearcase to eliminate frozen driveshaft first-th

I did get it into neutral and the prop spins so I assumed it was the engine that was locked, but I see the point that is could be the drive shaft. Will remove the lower.

So my sad story is that I did take the lower unit off and the engine is still locked up even after squiring PB Blaster in every crevice (e.g. cylinders) I could find. After that the only way it would turn was very slowly by hitting the flywheel with a heavy hammer and a piece of brass. Got it around 1-2 times but it’s still real tight all the way around. My current brainstorm is to douse it in PB Blaster in the horizontal position and let it set for a while and try to spin it again. If it lives it will be a miracle.

Your probably doing more damage trying to free it up at this point. Best to disassemble the engine and find out what's going on. Buy a service manual for a reference and go for it.