Topic: 1973 Evinrude Mate 2HP Issues – Page 2 – Antique Outboard Motor Club,Inc

This topic has 49 replies, 12 voices, and was last updated 5 years, 12 months ago by fleetwin.

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April 2, 2018 at 6:37 pm #73359
fleetwin
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US Member - 2 Years
OK, well the piston IS correctly oriented in the cylinder…But, I see a lot of rust on that cylinder wall. Did you hone the cylinder? If there are actual pits on the cylinder from the rust, this might explain the low compression.
It kinda looks like the previous owner tipped the engine upside down somewhat when he removed it from the boat, water trapped in the exhaust housing backed up into the cylinder and got trapped there causing the rust and pitting.
It is tough to prescribe what to do now….Are you sure you used the correct part number rings? You did not check the end gaps, so we don’t really know where we are at now…Rub you finger nails along those rust marks to see if there is pitting…Let us know…
April 2, 2018 at 8:36 pm #73360
shane-r13
Participant
Thanks for the reply. I havent had it honed, I have however used emory cloth and light oil since I took the photos. It seems to have helped but i worry about taking to much material off. To be honest i don’t know exactly what pitting will look like but I have to think what I see is pitting. I plan to remove the piston and rings again this evening and I can measure ring gap then. The rings I used are the standard sized rings, OMC part number 383920. But these rings had flat ends not the L-shaped which was stock. I’m starting to think that because of the different ends that I may not have received the correct rings.
April 2, 2018 at 8:43 pm #73361
shane-r13
Participant
Ok, so i just checked my local hardware store and they sell a honing kit for 20 bucks. Thinking I may purchase and use it. How would I know when to stop honing or how much material to remove? Just measure how much i’ve removed with a vernier caliper? If I go this route should I be reordering new rings that are .030 oversized? I’m thinking now that i’m may reorder rings since the set I got have different ends than stock. BTW, this is my first tackle at doing this type of work, I’ve done ring swaps and and gaskets, carbs etc, but never had to hone a cylinder.
April 2, 2018 at 10:17 pm #73365
fleetwin
Participant
US Member - 2 Years
Again, this is a tough situation…A conventional hone may seem to remove the rust/pitting, but might just be masking the problem…You will really need a super rigid hone, which would be hard to find for such a small cylinder bore…
The 383920s are the correct rings for the engine…But, were the rings you bought OEM pieces, or aftermarket? The ring ends should have notches to fit over the locating pins on the pistons, the ends should not be flat. So, I am guessing you did not get OEM rings…Rings with flat ends would have super oversized ring end gaps that would certainly affect compression…
No, please do not order .030" oversize rings, these will not work unless you have the cylinder bored to .030" oversize and purchase .030" oversize piston…
So, I guess I would probably pull the engine down again and post pictures of the rings you installed. Do you still have any pieces of the original rings left hanging around? If so, look at the ends of the rings to see how they cover the piston locating pins…Flat ended rings will not work correctly…
April 3, 2018 at 12:38 am #73372
shane-r13
Participant
Well I honed it out a bit. Smoothed the cylinder up nicely, still some pitting but i was afraid of taking to much off. My rings are wrong, flat ends no notches so the end gap is huge, talking over 30 thou. But I slapped it back together and put a tester on it and it bumped it up to 65psi. to me that seems like a decent improvement from 50psi. I’m gonna try tomorrow to start it and see if i even get it to fire. If it does i’ll be ordering the proper rings this time hopefully. If it doesn’t fire well i don’t know, i don’t want to toss a lot of cash into this with no guarantee it run again.

The pictures make the rust and pitting seem worse then when i look at it in person. Seems to really stand out in the photo.

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April 3, 2018 at 1:07 am #73374
fleetwin
Participant
US Member - 2 Years
OK, well those rings just can’t be OEM rings, and the big end gaps caused by the flat ends could surely explain the low compression readings… It seems strange that those rust marks did not go away while giving it the 50 cent hone job with the emery cloth, which concerns me.
You have got it back together now, so go ahead and try it, but I think you ought to go ahead and order the proper OEM rings…65PSI is pretty marginal for this engine, especially seeing that it has new rings…
I am very interested in finding out just where you got the flat ended rings, and if they were portrayed as OEM equipment…
If you order the new rings, please do not reassemble until you have checked ring end gaps in the cylinder, along with side clearance on the piston…
April 3, 2018 at 1:08 am #73375
need2fish
Participant
Pits will not hone out. Anything larger than the width of a ring will cause compressed fuel to leak by the ring. You can,however, ignore pits beyond the travel of the rings.

IMHO only cure for pits (as opposed to surface rust), is to bore out the cylinders. Unfortunately, I’ve never seen oversize pistons for a Mate (doesn’t mean they don’t exist).

Q: What did you squirt in the sparkplug hole, raw gas or mixed ? Raw gas won’t seal as well as fuel mix.
April 3, 2018 at 1:27 am #73379
shane-r13
Participant
quote need2fish:

Pits will not hone out. Anything larger than the width of a ring will cause compressed fuel to leak by the ring. You can,however, ignore pits beyond the travel of the rings.

IMHO only cure for pits (as opposed to surface rust), is to bore out the cylinders. Unfortunately, I’ve never seen oversize pistons for a Mate (doesn’t mean they don’t exist).

Q: What did you squirt in the sparkplug hole, raw gas or mixed ? Raw gas won’t seal as well as fuel mix.

I used mixed fuel to mist in spark plug hole.
April 3, 2018 at 1:30 am #73380
shane-r13
Participant
quote fleetwin:

OK, well those rings just can’t be OEM rings, and the big end gaps caused by the flat ends could surely explain the low compression readings… It seems strange that those rust marks did not go away while giving it the 50 cent hone job with the emery cloth, which concerns me.
You have got it back together now, so go ahead and try it, but I think you ought to go ahead and order the proper OEM rings…65PSI is pretty marginal for this engine, especially seeing that it has new rings…
I am very interested in finding out just where you got the flat ended rings, and if they were portrayed as OEM equipment…
If you order the new rings, please do not reassemble until you have checked ring end gaps in the cylinder, along with side clearance on the piston…

I agree i’m not satisfied with 65psi, but i thought it was decent considering the ring end gap I have with the improper rings. I bought the rings local, came in a bag with the correct part number so I never even looked twice at the rings them self until I got home and was slapping them on the piston. Foolish mistake. Ahh well live and learn. If it even fires once tomorrow new rings will be ordered ASAP because at least i know it will run with proper rings and at least more compression hopefully.

I’ll report back tomorrow with what happens.

Thanks for all the help and input so far! This site has become invaluable in my motor repairs.
April 3, 2018 at 1:37 am #73382
shane-r13
Participant
quote need2fish:

Pits will not hone out. Anything larger than the width of a ring will cause compressed fuel to leak by the ring. You can,however, ignore pits beyond the travel of the rings.

IMHO only cure for pits (as opposed to surface rust), is to bore out the cylinders. Unfortunately, I’ve never seen oversize pistons for a Mate (doesn’t mean they don’t exist).

Q: What did you squirt in the sparkplug hole, raw gas or mixed ? Raw gas won’t seal as well as fuel mix.

BTW there is a guy selling the .030 oversize rings and piston on eBay right now for $25usd. Very rare but they are out there. Just an FYI lol.

https://www.ebay.ca/itm/johnson-2hp-evi … 1438.l2649
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