74' Evinrude 25hp - 25402M

This motor came along with the boat that I recently purchase and I was hoping to get it running. The PO said it had a "solenoid problem" but he also said that is was an 18hp which in fact it is a 25hp. I know for sure that it is missing the spark plug wires (you can see this in the pictures below). What are the steps to attempting to start an electric start outboard?

There are quite a few wires and I am not exactly sure which is which.



I believe the spark plug wires clip into here.



Here is the control box it came with.

You have a LONG way to go before starting.
Those are not the spark plug wires, they are coil wires and the coils are missing. Pretty expensive too.
The engine has a funky ignition system consisting of points but it also has a power coil under the flywheel. Does the engine even turn over by hand?
You will need to address the carburetor and the water pump. From the looks of the engine that may be an issue as well due to long hours out in the salt water.

to add to what Pappy said - the 1970s OMC motors are pretty hardy machines
IF they are maintained properly.
#1 priority is to get a Shop Repair/Service Manual and Parts Catalog off of the internet (ebay) . . .
then, learn all about your motor.
Once all the missing and old parts are found and replaced, it can be a good running motor.

the service manual and parts catalog are two entirely different books.


good luck !!




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I just spent the last 3 months rebuilding a 74 evinrude 25, pull start, not electric start. I'll throw in my 2 cents real quick. Your missing quite a few parts, so you might want to consider finding a different motor before dumping a fair amount of money into a motor just because you already have it. I started with a complete motor, and probably have around $300 just in parts. I got it running and I'm sure it'll run for atleast the next ten years, but it was frustrating at times.

Do your research before putting money into it and see what the best option is. Some local libraries also carry maintenance manuals.

I want to thank everyone for their replies. It looks like I may just hold onto this one for a parts motor. I found a 78' 25hp Evinrude that is tiller and pull start, which is what I really want. Would most of the parts on the 74' be compatible on the 78'?

I am going to go look at the 78' today and I was wondering what should the compression be? It is in "good running order" what sort of price range would you put it in? I know it will vary by location but what's a ballpark number?

Jim, our Administrator, started this thread just for you !!! (well, all of us).
it is worth your read.

https://forum.tinboats.net/viewtopic.php?f=4&t=39389







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There were a lot of significant upgrades to the Johnny-Rudes in the mid 70's. Ignition changed from Points & condensers to CD style. From comparing the two on Boats.net there isn't a whole lot of similar part groups. Maybe the gearcase and the carb. The powerheads are different, the ignition is different, midsection is different.

There are definitely some shared parts, but not much. I wouldn't go into this thinking your existing motor would be a significant source of spare parts.

https://www.boats.net/parts/search/BRP/EVINRUDE/1974/25402M/parts.html
https://www.boats.net/parts/search/BRP/EVINRUDE/1978/25802C/parts.html

Good luck!

kofkorn that is unfortunate but thanks for letting me know.

Johnny, thanks for giving me that link, lots of good information there.

However I haven't been able to find what the ideal compression would be for a 78' 25hp Evinrude.
Also, how close should the compression be between the two cylinders?

my '79 Johnson 25 has 90psi top and bottom and it runs great.
I am running 50:1 and sometimes 40:1 gas mix. And now, non-ethanol.
I have seen several people here say a minimum of 80psi.
100 or more is gravy. Not more than 10% (??) difference.
Like they say, if the numbers are low and equal, it "may" be a leak in the head gasket.
Pappy was extremely gracious last year in walking me through
replacing the water deflectors and other items that are crucial in
getting the motor up to good running condition.

a Repair/Service Manual and Parts Catalog are highly recommended for any motor you own.