I recently obtained an excellent running 1957 Evinrude 18hp. It's going on my 14' aluminum boat (replacing a 1966 Johnson 9.5). There is a small oil leak behind the prop.

Here is a parts diagram and listings.

https://www.marineengine.com/p...tion=Gear+Case+Group

I want to replace the seal #35 and will also do o-ring #34 plus get a few spare pins #36.

My question is why are there 2 different part numbers for #35? Which do I need?

Any of them should work for #35, only difference is if they made 2 different shaft thicknesses for that lower unit. Serial number should differentiate that.

Is there a website I can put in the serial to tell me which I have?

What is the hull rated HP? If you put an engine that is above the rated HP, you will not be able to get insurance.

Hull plate is gone. It's an older boat that was given to me. I've got very little $ tied into this boat and not planning to insure... by very little I mean less than weekly groceries.

Just call your local dealer and order the parts......what are you going to save on those few parts to make the hassle of ordering the wrong ones worth it?

If you have an oil leak out of the gear case you will have water leak into the case. That water, over time, can damage gears and bearings, depending on the amount. Drain lube first into a clean jar. If it looks like water, primarily, or has a significant amount at the bottom, be prepared for other issues.

From the picture, one seal appears to have a metal case. If there are two shaft diameters then you would want to choose the inside diameter of the seal corresponding to that diameter. I have no idea how you would find this out without a service manual.

Those old engines weigh a lot more, so horsepower is relative.


Happy to see some parts are available. I have a '62 Evinrude that we used up to the early 90's, but stopped when I went to an even smaller boat. Sadly I think it's probably solid now, but I'd love to get it going again.

The "young guys" at a shop might not be able to help you. When I was just out of high school I needed to get a new shaft for ours. But the guys working in the local dealer couldn't help me because they couldn't come up with the model number. I Went several times, finally dragging the whole thing down there to show them there was no model markings. When the owner finally came back from vacation I went down and saw him. He said "Oh sure, the model number was in the serial number back then. These kids don't know anything." He went up in the attic and came down with the part. He a occomplished in ten minutes what the rest of them couldn't do in several hours over two weeks.

You will probably need other O-rings when you take it apart since they deteriorate with age.

You need insurance if you are on public waters and someone runs into you and liability kicks in.

So is the boat a flat bottom or a deep vee bottom? Also the older engines were rated at the crank while newer outboards are rated at the prop.

I'd suggest replacing every seal and gasket since you'll have it broken down that far

Then have pressure tested