Evinrude 25 hp Big Twin

[mtcabinfever]

I just purchased a 25hp Big Twin Serial number 25012-39608 and wanted to know year of motor, fuel mixtures, spark plugs, etc and how I go about getting a owners or repair manual so I can start my rebuilding process. What do all the number mean?

 

[F_R]

Re: Evinrude 25 hp Big Twin

25012 is the model number, and identifies it as being built in 1953-54. 39608 is the serial number. Up through 70000 is 1953, 70001-up is 1954. So you have a 1953.

Spark plug is J-6C gapped at .030". Fuel mix is 24:1. Lower unit takes 90 weight gear oil.

Evinrude service manuals for those years are not the greatest. Look for a Johnson service manual, 10th Edition. Kind of hard to find and $$. (Johnson had the same motor). Service manuals and owner's manuals are not the same thing. www.outboardbooks.com probably has an owner's manual copy.

Unless they have already been replaced, it needs new coils. So there is a good place to begin.

 

[1946Zephyr]

Re: Evinrude 25 hp Big Twin

Yep, I have the tenth edition sitting right next to me. I got mine at the Ken Cook Company as well. The bindings aren't the greatest, but a good manual to have. I may just have each page laminated and put it in a 3 ring binder. It covers from 1922 - 1964.
Like F_R says, the 1951 and up Big TWin, is virtually identical to the 1951 and up Johnson RD/RDS/RDSL except for the cover and the paint color.

 

[mtcabinfever]

Re: Evinrude 25 hp Big Twin

25012 is the model number, and identifies it as being built in 1953-54. 39608 is the serial number. Up through 70000 is 1953, 70001-up is 1954. So you have a 1953.

Spark plug is J-6C gapped at .030". Fuel mix is 24:1. Lower unit takes 90 weight gear oil.

Evinrude service manuals for those years are not the greatest. Look for a Johnson service manual, 10th Edition. Kind of hard to find and $$. (Johnson had the same motor). Service manuals and owner's manuals are not the same thing. www.outboardbooks.com probably has an owner's manual copy.

Unless they have already been replaced, it needs new coils. So there is a good place to begin.

Do you know what i would gap the points at?

 

[F_R]

Re: Evinrude 25 hp Big Twin

.020"

 

[1946Zephyr]

Re: Evinrude 25 hp Big Twin

.020 is pretty standard with all OMC singles and twins, especially those with the universal style ignition, used from 1951 on up to 1976.
Earlier stuff may vary, but those are pretty much all .020 as well. I worked on an old Merc 1000, one time, that set at .010. Talk about a pain to get set right and stay there.

 

[kfa4303]

Re: Evinrude 25 hp Big Twin

This link may help you get that old Big Twin up and running.

http://www.duckworksmagazine.com/04/s/columns/max/24/index.cfm

 

[mtcabinfever]

Re: Evinrude 25 hp Big Twin

.020 is pretty standard with all OMC singles and twins, especially those with the universal style ignition, used from 1951 on up to 1976.
Earlier stuff may vary, but those are pretty much all .020 as well. I worked on an old Merc 1000, one time, that set at .010. Talk about a pain to get set right and stay there.

So points for a 1955 should be same or fit my 1953?

 

[samo_ott]

Re: Evinrude 25 hp Big Twin

Yep, as mentioned, they're the same from '51 til the mid 70's or so from 2-40hp.

 

[1946Zephyr]

Re: Evinrude 25 hp Big Twin

Yep, that is correct sir. Same coils, points and condensors and even the same spark plugs.

 

[steely51]

Re: Evinrude 25 hp Big Twin

if the fuel mix is 24 to one , should not the gear lube be hypoid?

 

[F_R]

Re: Evinrude 25 hp Big Twin

That's what I meant when I said 90 weight gear oil. I dunno, do they still label that stuff as "Hypoid"? I haven't noticed. A better modern label might say Hi Vis Outboard Gear Lubricant.

BTW, if you are old enough to remember such things (like I am), "Hypoid" refers to the rear axle gears on a car. On the real old ones, the drive shaft pinion gear was on the center line of the differential ring gear. Later, they put the pinion below the center line to reduce the car height and drive shaft hump in the floor. The lower pinion setup was called Hypoid gears, and required better lubrication than the antiques used. ANY modern gear oil is going to be better than back in those days.

 

[SeaKaye12]

Re: Evinrude 25 hp Big Twin

It is a miserable interface on their website...but that manual (all 674 pages of it) is available for reading online at:

http://boatinfo.no/lib/johnson/manuals/1922-1964johnson.html#/0

liquidnirvana also has it posted on his webshots page:

http://rides.webshots.com/album/559126452pjSnFo

Not quite like owning it...but better than nothing.

Chuck

 

[1946Zephyr]

Re: Evinrude 25 hp Big Twin

Interesting F_R. Never knew that little tidbit on car rearends. I kinda thought that outboard lower unit oil was a little bit different than the typical 90 weight gear oil. Isn't it?

 

[mtcabinfever]

Re: Evinrude 25 hp Big Twin

Can anyone tell why I have this appendage on the side of motor support area which seem to be interfering with upper shaft when motor is turned. It appears to have resolved itself overtime but was curious why this happened?

 

[WalterRay1231]

Re: Evinrude 25 hp Big Twin

Old thread- but I believe the primary difference between regular gear oil and marine gear oil are additional additives for corrosion resistance and the ability to absorb a limited amount of water and remain somewhat similar to a lubricant. My 58 should be similar to yours- I'll take a look at it tomorrow and see if I have the same 'appesage' if you haven't already figured it out.