Oversized Rings?

[Buccaneer]

The Thor built Sea King I tore apart is missing it’s piston rings.
It’s a 2" bore, bored .020 over.
The ring grooves in the piston are 1/8" wide.

I don’t have many resources to look up ring sizes, but did find
some old Evinrudes with a 2" bore with rings 1/8" wide.
Don’t know if they ever made "oversize" piston and rings for
these engines, but the standard size ring parts number are..
100710
200006
200739
I had no luck searching for these rings, let alone their oversize versions.

Found some Johnson "oversize" ring parts numbers, but none were
for 2" bores.

Otto’s Engine Works don’t say anything about "over size" custom rings.
Not even sure if it has the correct oversize piston in it at this point
as far as "height, dome shape, etc. The cylinder is "headless", so
there was no way to see the piston and porting interaction before
I pulled the cylinder.

Any ideas on over size rings?
Thanks.

Prepare to be boarded!

[pm-t2]

Measure the skirt on the piston to verify whether it is standard or oversized.

As far as I know, Otto can provide a ring in any sizing you want, provided you’re willing to pay for it.

FWIW the 2 inch bore covers several Evinrude motors, ranging from the early 30’s Sportwins and Fisherman, and up to the early 40’s Elto Lightwins. Some models of the Jr Quad and Sportfour also use the 2" X1/8" ring as standard issue. But if your bore is really punched out 20 thou over, those rings won’t help you anyway.

I’m assuming you measured the cylinder bore with a telescoping gage and micrometer, or a suitable bore gage set up and calibrated to suit. If the hole measures 1.020" +/- a couple of thou, your only option is to use the corresponding rings.

Hope it helps.

best,
PM T2

[Buccaneer]

PM T2, I measure the bore, and indeed it’s 2.020, and
the piston is stamped .020, so that was confirmation.
Anyone know if they offered over sized rings back in
the day for those early Evinrudes and Johnsons?

Prepare to be boarded!

[lyks2tinkr]

You may also want to check with Hastings.
I’ve had great service and performance with there rings.
Very dimensionally consistant

[garry-in-michigan]

I was also unable to find Evinrude Part numbers for your oversize piston rings . . . 🙁

[Buccaneer]

Thanks for looking Garry.
I’ve found rings at Hasting’s once for a 5 hp Gale, but
I think they wanted about $128 for the set!

Prepare to be boarded!

[Anonymous]

I have bought over size rings in stock off the shelf from Otto Engine works, at their regular price. For a .040 over size ring set for a Johnson SR45. Also they had in stock over size rings for another project, 1916 Evinrude row boat motor .020 over size, at their regular price. CALL them, they had a huge amount not listed.

[Buccaneer]

I just heard back from Otto Engine Works.
If I understand his reply correctly, I think he can help me out.
===============
Hi Tom-
I have plain compression rings here at $5 per ring plus shipping and handling. That cost depends on where you are at. These rings do not have any pin clearance for any pins that might be in your grooves.
Thanks,
Dave Reed
Otto Gas Engine Works
2167 Blue Ball Road
Elkton MD 21921-3330 USA
phone 410-398-7340
http://www.ringspacers.com
http://www.pistonrings.net

On 3/25/2018 9:27 AM, Tom wrote:
Hello, I’m wondering if you offer rings in "over size"?
I have a 1937 Thor outboard that’s missing it’s rings.

The cylinder bore is 2.020 and the piston
is stamped as being .020 over sized.
The rings are 1/8" thick.

Thanks, Tom

Prepare to be boarded!

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