1990 & 1976 OMC 25HP SS - part interchange

[iam2sam]

I currently have a 1976 25HP Evinrude short shaft motor. Good compression, runs well, but needs lower unit seal replacement, which I'm about to attempt. I found the same basic motor branded Johnson vintage 1990 offered for sale at a reasonable price, ad claims good running condition. I was shopping for a parts motor anyway, this might give me an actual working backup instead (I'd use whichever motor ran best as my primary.) It could still happen that I might someday want to swap parts from one to the other. Can someone give me a brief synopsis of which parts (or systems) would _not_ easily interchange between motors? Thanks.

 

[racerone]

No chance of any parts interchanging between those 2 motors !

 

[Chinewalker]

I think the lower unit drain plugs have the same part number. Outside of that, not much...

 

[jimmbo]

An 18hp Evinrude and 20hp Johnson of the late 1960s thru 1977 would be very good donor motor. Almost all the parts were the same as the 25

 

[iam2sam]

So, is the 1990 motor completely different in design, or is it just that the accumulation of evolutionary changes makes part swapping impossible? I like the design of my 1976 'Rude, especially the light weight.

 

[iam2sam]

An 18hp Evinrude and 20hp Johnson of the late 1960s thru 1977 would be very good donor motor. Almost all the parts were the same as the 25

That's helpful. Thanks.

 

[racerone]

Simple----1976 was the last year of the 22 cubic inch model.---First produced in the late 1950's

 

[iam2sam]

At the risk of belaboring this, I want to make sure I correctly understand the series of my motor, as it appears I was previously confused on that issue. My serial number is E0005739, which (based on my research of that model last year) and appears to be model 25652E, dating from ~1976. It is a 2-cylinder motor. From what you are telling me, this model shares (at least some) parts with the >=15HP OMC two-cylinder engines dating from ~1955 to 1976 (even those with the very different looking "old style" covers) but not with anything of more recent vintage? Does that apply to both powerhead and lower unit parts? Thanks.

 

[F_R]

Yes, the 22 cubic inch motor came out in 1955 and ran through 1976 (even before 1955 but less cubic inches). But there were many small changes over that 20 year period, so while many parts stayed the same, you cannot assume that all of them are. Yes, evolution is real---at least with outboard motors. After 1976, the 25hp motors continued to use the old two-piece gearcase for a few years but the 35hp got a thru-prop-hub exhaust unit. And the 25 was no longer the 22 cubic inch powerhead, but it was similar to the very different 35hp powerhead

I'm confused, is 25652E the actual model number or are you assuming that? The serial number doesn't mean beans because Evinrude started them over every year.

 

[iam2sam]

...
I'm confused, is 25652E the actual model number or are you assuming that? The serial number doesn't mean beans because Evinrude started them over every year.

That's a good question, I hope I have an equally good answer The motor is in winter storage, so I can't go look at it, but if the model number appears anywhere on the motor, than that is where I got it. Otherwise, I must have followed a trail of breadcrumbs on-line to arrive at it...