Topic: dented pistons – Antique Outboard Motor Club,Inc

This topic has 10 replies, 7 voices, and was last updated 8 years, 2 months ago by wedgie.

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January 29, 2016 at 10:28 pm #3511
wedgie
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Hi all

Picked up a seized QD 18 today. I looked through the plug holes and noticed both pistons were dented by a p/o trying to free it up by pounding on them with a blunt instrument. Well, I pulled the head (only broke one bolt) and managed to free it up by liberal use of some seafoam deep creep and a 2×2 piece of wood for a drift. My question is: does the damage to the piston necessitate replacing them ? They are not broken through, but are dented about a 16th of an inch. will the dents create hot /cold spots ?
January 29, 2016 at 10:32 pm #31015
Anonymous
I would just smooth the sharp edges so as not to have a hot spot.
January 30, 2016 at 12:45 am #31030
frankr
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US Member - 1 Year (includes $3 online payment fee)
Use ’em. But how is the rest of the powerhed–rings, bearings, etc?
January 30, 2016 at 12:48 am #31032
billw
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US Member - 2 Years
Me too. The fate of the world doesn’t usually depend on our motors. Not usually a life and death situation. The pistons will probably be fine for a few runs, now and then, by a hobbiest. However, my experience with stuck QDs and FDs has often shown that you’ll also have rust damage on the crank. Have you seen it yet? To me, that would be more worrisome than the pistons….

Long live American manufacturing!
January 30, 2016 at 1:03 am #31036
fleetwin
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US Member - 2 Years
Hmmmm.
How about the wrist pins, are they sloppy? I am guessing this is why the pistons are dented.
Oh, OK, just reread the post.
The previous owner dented the pistons with a punch trying to free them up, correct?
If so, I wouldn’t worry about it, maybe just try to smooth the ridges down with some emery.
But, you still want to check for sloppy wrist pins.
January 30, 2016 at 2:01 am #31037
wedgie
Participant
I haven’t opened it up yet, but there was a small amount of rust apparent in the cylinders. There is some slop too, but I’ve seen worse. I will clean up the head and gasket and put it back on to see what kind of compression there is. If it’s no good, that’s ok ’cause there are lots of good usable parts including a really nice cowl and emblem,a good prop that I need for another QD hanging on the rack . I haven’t checked the gearcase yet , but it spins freely and looks good on the outside with no breakage. Got it cheap too 🙂 !
January 30, 2016 at 3:58 am #31043
fleetwin
Participant
US Member - 2 Years
Good plan, I’m sure it will clean up and have decent compression, and run great too. Remember, those QDs don’t have a lot of compression…
January 30, 2016 at 6:10 am #31050
wedgie
Participant
Compression is low, under 50 psi on both, and as was suspected there is rust in the crankcase. No big surprise as I have seen that a few times on the QD’s as well. I will pull it apart completely tomorrow to see just how bad it is, but for now, a view into the intake:
January 30, 2016 at 1:02 pm #31058
chris-p
Participant
Ewwww, you can see why the motor was stuck. That one will have to be opened up.
January 30, 2016 at 5:25 pm #31078
Mumbles
Participant
Need a crank? I think I have a few usable ones.
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