Back on the boat

[melinprov]

Finally-we had snow 2 weeks ago after 90 degree weather then much rain, I managed to start the rebuild on the engine  ( aq130c ) and do some fiberglass work I didn't do last year. On the engine I cant crank it by hand-I wanted to do a compression test- and its pretty clean but there is rust around one of the pistons from below. Can you lift off the head without taking off all the top stuff? it doesn't seem to specify in the work manual I have-here's some pics

[melinprov]

here's the top

[Plugcheck]

Some engines have head fasteners below the rocker arms, some do not.   Pull the rockers and stay organized, which rocker, which pushrod, etc.   I don't see any discoloration on the rod caps which happens on spun bearings.

[melinprov]

so this is not what I expected...I thought I would find one rusted out-stuck piston. Here is a screw someone dropped into the engine!--this could be better than I thought I was going to find. There appears little damage to the ports above but I fear that the screw probably marred the piston-sleeve and rings. I did find some water in the engine oil back 2 years ago but it seems to have been confined to below and some condensation that went up. Otherwise the walls I can see are smooth

[Plugcheck]

Might be one of the screws that hold the carb bottom together.   If you can dig that screw out, does the engine turn over by hand?    Any wall scoring?  Might be able to do a little clean up and back in service.  Save rebuild for winter maybe?

[melinprov]

YES, I had a few things to do before I tried to turn it. I left the screw in the piston- it is welded and flattened into the piston I think it just stopped it from finishing its cycle... and the walls of that piston are smooth with no scratches- I see a little nick over the side of the port but it did impact the ring a little. Everything turns smooth and all the other piston walls are smooth as well-I'm sitting back to think this over now. a compression test was what I started and it would not turn and now that the heads off it moves smoothly but not effortlessly.

[still_fishin]

That screw was probably making contact with the head not allowing you to turn the engine.  Your going to need to pull that screw at a minimum. 

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[melinprov]

 I'm wondering if I can blend it in? or if I should just replace one piston or some how rework it, never was too good with welding and metalwork

[Plugcheck]

The piston top is thickest in that area.  Hopefully no damage to ring land.  Pull the screw, grind off the sharp spots.   Blending the screw might leave a part to fall off, possibly causing more damage.   If you're not confident in your work, pop the rod cap off, and take the whole piston and rod into a machine shop.  Maybe they can recommend welding, or maybe replacing single piston?  Removal would be the best way to know if ring lands got damaged.

[melinprov]

Sounds like a plan Plugcheck, You and Still fishing are right. At work on Monday I will talk to one of our Mechs and welder to see what they think. I'm not beyond just prying or grinding it out myself or even having one of my co workers do it- but as you say the material left behind could do damage. It is possible that this is all I need to do. I may put in all 4 new also because I can go off the stock weights on the piston assemble but to be accurate maybe I should replace all or open up all to weigh them and there's still that discoloration on 2 of them which I suspect could be bad rings also. but once I take care of one I can do the compression test and see where I am.

[melinprov]

so here's a update...the main Mechanic at work said just pick it off or grind it and then check your wrist pin and bearing and if I need it welded He would do it. When I got home I was considering what tool to use on this. While I was pondering I reached down to touch the screw and it just lifted off-I had put a ton of wd40 on it and it seems to have loosened it up. Do you think I could get away with running this piston like this? I'm going to do a compression test after my irrigation Wednesday to see how it comes in on all four. I would clean it up also as you can see the build up and small grains and flecks above the top ring and around the valves but I think this missed the ring now that I have removed it and got a better look.

[melinprov]

you can see some of that oil in the water just below the valves here -is it possible that the valve being open collected rain water or that while it was running it was sucking in water in that cylinder because of low or no pressure? i wish I knew how long the previous owner ran it like this.

[Plugcheck]

I would suggest a little massaging of that piston top to knock of any sharp edges caused by the screw being pressed it it.   You're not trying to blend it smooth, just knock the sharp points off to prevent knocking.  I've had several engines over the years with similar issues, they ran for years afterwards.   For curiosity, have you any idea where the bolt came from?  Valve cover or carb bolt?

[melinprov]

I'm really not sure where the screw came from, it does seem to be stainless. I have been told the previous owner did some or had some work done on the motor, so someone has been in it. I did look at the carbs and all the screws are there. If it did come from the carb I would think there would be damage to the valve? and I don't see any. A mystery. I never tried to start it myself.

[melinprov]

so I did grind it smooth with a Dremel and all seems good-- still trying to figure out the oil cooler, today i repainted the block and engine parts-waiting on the rest of my gaskets and I think I will put it back together as I have gone through it and all looks good-here's the old and new engine colors