Mecoa .46 Mar-Flipped Boat-Engine Wet-Piston Will Not Go TDC

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Mecoa .46 Mar-Flipped Boat-Engine Wet-Piston Will Not Go TDC

Postby Green Jumper » Thu Sep 24, 2009 5:21 pm

Hi

Have a relatively new .46 marine, have run about 12 oz of 15% fuel - ran good until sport hydro went airborne - flipped - but landed right side up; Engine ingested water never-the-less. Unable to rotate crank but about 120 degrees +/-; Piston sticks in sleeve when attempting upstroke. Can see piston move up and down with crank rotation so rod apparently not broken.

Suggestions on repair?

Do I need to now lap piston/sleeve to permit full rotation?

Please advise - I like the engine for this application - very pleased.

Thanks

Art
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Postby SteveM » Thu Sep 24, 2009 5:36 pm

When you went to turn over the motor after the flip did you remove the glow plug first? If not, then you likely have a hydraulic lock. Best to remove the glow plug, pinch off the fueltubing, open the throttle to full and turn over the motor and use WD-40 in the carb mouth. There will be lots of spray so put a rag on top of the motor to cover the glow plug hole.
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Postby Green Jumper » Thu Sep 24, 2009 6:36 pm

Hi

Thanks for your comments. I failed to mention that glow plug was removed and light oil was flowed into engine through carb and glow plug hole when trying to rotate crank.

Before incident, engine (virtually new) piston/cylinder fit was tight, with considerable resistance when rotating crank and piston approaching TDC (tapered fit) with glow plug out. I routinely start ABC engines with glow plug slightly loose and then tighten once engine is started.

Piston/cylinder fit appears to be much tighter now since the incident - free movement of crank/piston near BDC but extremely tight to point that I do not want to force on upstroke.

I am wondering if sudden cooling upon ingesting water caused cylinder to shrink or piston to expand, beyond tolerances - never had this happen before.

Suggestions?

Thanks Again!

Art
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Postby SteveM » Fri Sep 25, 2009 3:24 am

Most ABC engines have a tight fot at TDC due to the tapered sleeve anyway. Not sure what happened with yours though as it seems to have become tighter after running.
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Postby Green Jumper » Fri Sep 25, 2009 7:05 pm

Good Evening

I have disassembled the engine at this point. The rod appears to be fine and the piston and cylinder appear to be the issue. The piston will not move high enough into the cylinder due to tight fit. I am currently trying to heat the cylinder and piston (toaster oven) with intent to allow the assembly to cool slowly with hopes that they will return to normal fit. If this does not work, will attempt gentle lapping to the point where piston can travel to normal TDC height.

Suggestions or your own experiences are appreciated

Thanks

Art
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Postby Green Jumper » Sat Sep 26, 2009 9:29 am

Good Morning - Update

Piston aand cylinder fit appears to be restored after heating in toaster oven and allowing to cool.

Had heated cylinder first by itself, allowed to cool, then heated piston/cylinder assemby together, allowed to cool.

Engine reassembled and feels good, so will attempt to start when I can.
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Postby SteveM » Sat Sep 26, 2009 9:41 am

You may want to check on the oil content of your fuel. I alwats liked to add an ounce of Sig AA castor oil to my gallon jugs as extra instrance. Your motor might have run a bit lean during the initial tank causing the tightness.
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Postby Green Jumper » Wed Oct 14, 2009 11:37 am

Hi!

Update: Was able to test run the engine on the boat with cooling water supply hooked up to engine (milk jug full of water with hose to head); engine started and ran ok without load - all seems to be OK. Now if the rain would just quit long enough to get to the pond, I will be able to run the boat.

Thanks

Art

PS: Running 15% nitro fuel, 18% synthetic oil, with additional slug of castor from Walmart added
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Postby chiefss » Wed Oct 14, 2009 3:16 pm

More than likely the cold water hitting the hot cylinder shrunk the ABC cylinder just enough that the fit became too tight. Heating it and letting it cool slowly apparently solved the problem. ABC cylinders do expand when hot giving a perfect fit while running. That's why you don't what to run they soppy rich. The cylinder never reaches operating temp.
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Mecoa .46 Mar-Flipped Boat-Engine Wet-Piston Will Not Go TDC

Postby Green Jumper » Tue Dec 29, 2009 11:50 pm

Hi

Happy Holidays to all!

Hydro with Mecoa .46 has now been run at the pond - all OK since heating the cylinder and piston assy. On last time out, got engine up on pipe for first time - need to lengthen the header pipe slightly to be able to get on pipe at slightly lower rpm.

Engine is running fine!

Take Care

Art :D
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