HELP! Can I use '68 OS piston for '62 rebore?

[Intermediate Mariner]

Hi Guys,
I am working on a '62 Evinrude Lark 35530 40hp.

Have a bad cylinder and need to rebore it.

The original oversize cylinder for that motor (#378697) is NOT AVAILABLE ANYWHERE IN THE WORLD that I have found, not on ebay, not anywhere.

The '68 piston is a little bit more available and there are a few out there. I was able to find an oversize piston (#383069) and OS rings (#380109).

The blocks are different part numbers but look identical. I called bombardier and they actually talked to me (you know how they don't like to talk to you unless you have a '98 or newer). They said c.i.d. was different but both years are listed at 43.9 cid.

The '62 piston ring side clearance is 0.005-0.0065.
The '68 is 0.0045-0.007 (greater?).

The pistons look visually identical to each other and measure the same height. The rod is a DIFFERENT part number but the wrist pin is THE SAME (some light at the end of the tunnel). The underside is the same visually. The '68 piston also has a larger flat spot on top than the '62.

Can I use this '68 piston in the '62 motor? What side clearance?

Thanks!

Shawn T
Wichita KS

 

[1946Zephyr]

Re: HELP! Can I use '68 OS piston for '62 rebore?

Well, 62 was the first year they went to a 2 ring piston and lower compression heads. I can't see why it wouldn't work if everything measures out the same.

 

[Intermediate Mariner]

Re: HELP! Can I use '68 OS piston for '62 rebore?

Thanks Zephyr for the reply.

They both have 3-rings.

So the flat spot on top of the piston is nothing to worry about? What do you think about the clearance discrepancy?

Thanks again for taking the time to reply. I haven't had the best luck with this forum... you are the only one that answered this one and my last nobody did.
Thanks again for the time sir!

Shawn T

 

[wilde1j]

Re: HELP! Can I use '68 OS piston for '62 rebore?

Have you tried aftermarket pistons (Wiseco, GLM, etc.)? There may be more variety there.

An information source and parts source for old motors: http://www.aomci.org/
Pistons and most mechanical parts, even for very old motors are still available. The trick is knowing the sources and AOMCI members do.

 

[Intermediate Mariner]

Re: HELP! Can I use '68 OS piston for '62 rebore?

Holy cow thanks! I will try them.

 

[Intermediate Mariner]

Re: HELP! Can I use '68 OS piston for '62 rebore?

I went there and posted a webvertise and I hope someone contacts me. I wonder what in the heck folks do for rings on late 50's and early 60's for rings.

I tried a couple aftermarket places but no one seems to have anything that old.

 

[F_R]

Re: HELP! Can I use '68 OS piston for '62 rebore?

1962 uses 378695 (standard)
1968 through 1970 uses 383068 (standard)

Both 378695 and 383068 are superseded by 384698.

I recently tore down a 1964 that had one of each in it. They must have done just fine because it appears to have run about a bazillion hours since replacement of the one piston.

 

[wilde1j]

Re: HELP! Can I use '68 OS piston for '62 rebore?

Look at the links section of the AOMCI site. Places like Laing's Outboards have a lot of uncatalogued stuff.

 

[Intermediate Mariner]

Re: HELP! Can I use '68 OS piston for '62 rebore?

Thanks FR

That line below is GOLD, thanks. So I should be looking for 384698 then?

1962 uses 378695 (standard)
1968 through 1970 uses 383068 (standard)
Both 378695 and 383068 are superseded by 384698.

Thanks Jim, I will try Laings, good to know. Uncatalogged is the key. Alot of companies just go by year.

Thanks Gents-
Shawn T
Wichita, KS

You can always get 'em running!
"Hey where did you get that old outboard?". "It was buried in my back yard!"

 

[F_R]

Re: HELP! Can I use '68 OS piston for '62 rebore?

Actually, any of the three numbers. If you were to order a new one under the old number they would send you the latest one.

 

[Intermediate Mariner]

Re: HELP! Can I use '68 OS piston for '62 rebore?

Thanks FR, I've seen that before at the marine dealer, she'll ALWAYS come back with a different number it seems.. my luck.

OK, so, I am safe to order 380108 as a replacement for 378695??

I really appreciate the time FR. I promise to post clips of this project, and it's a project! I still need to finish the transom so I can hang the motor on. It's a Red Fish (the one without the fins, I think its a 60 or 61). It's pretty small and I bet it will fly with the rude 40hp!

I sure would like to go all vintage on this. I am going to have to hit the salvage yards for the dashplates and stuff (the motor had a Gale on it but someone stole it out of my driveway... and it was locked up!!). I have a rats nest for a junction box so thats another day (as is the control box for which i am missing some parts inside). This motor is just a piece of the project, whew!

 

[Intermediate Mariner]

Aomci

Aomci

wilde1j,
Thanks again for the aomci. I was able to post a message as a guest and I have had a couple guys respond with parts in hand for decent prices.
Good Tip!

 

[Mr5Keepers]

Re: HELP! Can I use '68 OS piston for '62 rebore?

CAREFUL!!
You have several things to consider when using "non-stock" pistions...

1.. wrist pin bore diameter
2.. piston skirt length from wrist pin center to bottom of skirt..(Clearence between piston and crankshaft or rod at BDC.
3..Ring locating pins - these hold the rings in place an keep them from snagging in the ports! VERY IMPORTANT!!!!!!!!
4.. Piston dome height from wrist pin center to top of piston. Clearence for pistion to head at TDC.
5.. ring land location.. needs to be close!
6.. piston to wall clearence is determined my the original motor specs! Not the motor the pistons come from!!

#3 is VERY IMPORTANT!! This will cause catastrophic engine failure if not EXACT!!

Good luck - break it in varying the rpm for a few weeks.. it will last A LOT longer.. use a minor amout of extra oil the first time.. extra oil just keeps it from breaking in efficently.

 

[1946Zephyr]

Re: HELP! Can I use '68 OS piston for '62 rebore?

Thanks Zephyr for the reply.

They both have 3-rings.

So the flat spot on top of the piston is nothing to worry about? What do you think about the clearance discrepancy?

Thanks again for taking the time to reply. I haven't had the best luck with this forum... you are the only one that answered this one and my last nobody did.
Thanks again for the time sir!

Shawn T

Oh, they still did have the 3 ring pistons. I know the heads and cranks were changed, but I thought the pistons went to a 2 ring set up. It's been a while since I tore into one of these. The older 35's were actually the most recent I've done.