Piston ID Help Please

[ausf233]

Hi guys,

Need your help to identify this piston. Pulled from an Aussie made 7.5hp vertical twin water-cooled outboard with a 2 1/8” bore, however I suspect the piston itself is American made. Unfortunately there are no carting marks or numbers.

I am in need of 2 pistons complete with rings, either new or used, but if used must be in good useable condition.

Thanks & regards,
Spiro

[billw]

Okay, I will at least comment that I have never seen anything like it, with only two, fat rings like that….

Long live American manufacturing!

[frankr]

The 7.5hp Evinrudes and Johnsons of the 1950’s are 2-1/8" bore. Without having one in hand, I have no idea how the rest of it measures up.

[Mumbles]

Here’s an AD (7.5) piston for comparison. The rings it uses are 3/32" thick.

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[ausf233]

Thank you guys, appreciate the help thus far. Sorry also for my delayed reply.

The piston presented by mumbles is dimensionally close, but its not quite the same.

Considering suppliers to say Evinrude, Johnson, Mercury and Chrysler, is the a piston manufacturers catalogue or similar that I may be able to refer to?

Alternatively, is there anywhere I can find bore and stroke dimensions for the more common outboard brands from say the late forties through to the sixties?

Any other ideas would also be welcomed.

Thanks & Regards,
Spiro

[garry-in-michigan]

Looking at Chrysler specs – the 1965 through 1967 nine horse has a 2.1250" bore. After that 2.1875" was standard. . . 🙁

[james-davis]

Johnson KR-55-65 is that size bore and wrist pin, I believe it has two wide rings, that’s going back in years.

[kees]

.
about the KR-55
most alternate firing twins has ports in the pistons, do they ??
what about the KR models ?
( at least ..a lot of these models , I guess )
I think, you need pistons from an opposed twin what comes close to
your search

[ausf233]

Thanks guys, all great information but I fear I am no closer.

Is there a supplier of early outboard pistons that I can possibly reach out to? If so, I could forward my photos to them in the hope that they may be able to draw a match.

Thanks & regards,
Spiro

[joe1]

That piston looks just like my Lockwood chief piston mine are 060 over but are marked I was told that they where Judson pistons 1929 and have the 2 fat rings an Evinrude bought out Lockwood. There ACE motor mite be the same it is there smaller motor

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