mid 50’s evinrude, powerhead swapability between 25-30-35 engines

[Doug]

When looking for a good used powerhead will these 3 sizes swap directly between the 25 30 and 35 hp engine frames. ?? I thought I an original spec sheet on these, referencing all three of these motor sizes with the, ci. bore and stroke all obviously different but yet classed into a family including these three. Thanks…

P.S. my engine frame is a 1954 Evinrude 25 originally.

I got a few I have had a long time but can always use a few more going into retirement.

• This topic was modified 3 years, 10 months ago by Doug.

[frankr]

I may be wrong, (probably) but I have the feeling that none of the ’55-up will fit the ’54 exhaust housing adapter plate. Interesting question

[outboardnut]

folllowing

[Doug]

I working on buying a 14′ 50’s era aluminum runabout that really appeals to me to hopefully attend some AOMCI events with cruises and have also found a pretty darn nice original 54 25hp evinrude to mate with it. I wanted a 30/35 but this engine was so nice I had to buy it, it will be plenty if not compatible either way and also too nice to be swapping parts for that matter, mostly curious about the interchangeability of parts in these engines through the 50’s generations. Like I said I saw an original publication with the 3 sizes listed as so similar they called out the bore and stroke for the 25,30,35 for comparison. I am not even positive of the year of that chart. I am still trying to learn more about this larger family and size range. I have had my 5.5’s for over 25 years but none larger.

I got a few I have had a long time but can always use a few more going into retirement.

[frankr]

That basic engine was made for over 20 years, with many evolutionary changes along the way. So you almost have to specify what part you are wondering about. For example “wristpins”, or “cylinder head”.

[larkbill]

Even if the power head bolts down you still will have other issues to resolve. Since the metal cowls of that era attached to the power head those changed a lot and even some between E and J. If you decide to try it be sure to document with pictures. You can be the NEW expert on the subject.

As an example I just swapped a ’69 25 hp power head onto a ’60 18 hp. Both have fiberglass tops and free standing belly pans. Should be a piece of cake. Except the exhaust section of the 25 is much different plus it was the newer design that didn’t need the baffle under the powerhead. At least I got to closely inspect all my rubber mounts. And now I have the World’s Fastest Evinrude 18 hp.

[opposedtwin]

Just my 2 cents. Replace the 25 (if it needs replaced) with a 25. Run it on the runabout for awhile. Keep learning of all the other RD/Bigtwin options as far as color, styling, etc. Eventually you may want to upgrade to a new/bigger/different motor. Maybe, maybe not.

Doing a ph swap may cause big headaches and ultimately may not be worth it. Learn more first, THEN you can make a well informed decision. Patience is the key.

Also, you may find as I have that RD/Bigtwin models are relatively cheap and abundant. It seems nobody wants them lately.

Good luck and have fun!

Scott
Again, just my 2 cents….

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