Vintage Evinrude Block Troubles..

[frustratedboater]

Greetings all:
I recently purchased an Evinrude Big Twin 30hp motor Partl # 15022 (great motor) and noticed a "clunking" sound when I spun the flywheel. After ripping it down, I discovered that the bottom cylinder has a major score in it, as well as the top cylinder just starting too. It looks like the wrist pin clips were installed incorrectly, and the pin dropped and gouged a grove about 1/4" deep. Looks like someone took a router to the cylindr wall. I found the corner piece of the wrist pin clip in the gouged area, which tells me somehow it slipped out. I would like to continue rebuilding this vintage beauty regardless of the situation.

So,..... I am looking for anyone who may have resouces in finding another block, pistons, and rods off a scrap motor? I saw a 25hp powerhead on Ebay, but the block numbers were not a match (I was hopeful). Thanks in advance for any suggestions.

 

[JB]

Re: Vintage Evinrude Block Troubles..

Try tcoutboard.com, frustrated.

Good luck.

 

[Chinewalker]

Re: Vintage Evinrude Block Troubles..

The 1955 25hp block is just about the same as the 1956 block. The difference in power comes from the change in piston and cylinder head design between 1955 and 1956, as they went from a 5:1 compression ratio to a 6:1 ratio. So, if you find a 1955 block, and can install 1956 30hp pistons with a 1956 head, you'll have a 30hp...

That said, if you are looking for a complete powerhead to just bolt on, a 1955 25hp powerhead will work (at 25hp, which you probably won't notice by seat-of-the-pants reckoning) as will the 1957 and 1958 standard 35hp powerheads (not the "silent" series ones).

- Scott

 

[samo_ott]

Re: Vintage Evinrude Block Troubles..

Scott, what are the "Silent Series" ones? I have never heard of them?

 

[ezeke]

Re: Vintage Evinrude Block Troubles..

"Quiet" !955 25HP:

http://www.old-omc.de/index2.html

 

[Chinewalker]

Re: Vintage Evinrude Block Troubles..

The "silent series" 35 hp powerheads are the ones used in 1958 & 1959 on the motors with the fat-looking double-wall mid-section and bucket cowlings. The powerhead base pattern is different from the standard 35hp models that used the clamshell cowlings.

The 1955 25hp versions were called "Aquasonics", but it was a different silencing method. That year was the first with the rubber-mounted mid-sections, which were used on later "standard" Big Twin models well up into the early 1980s.

 

[samo_ott]

Re: Vintage Evinrude Block Troubles..

Funny, I don't have any of those years... I have a 56, 57 and 60 big twins. No wonder I don't know those types! thx.

 

[Chinewalker]

Re: Vintage Evinrude Block Troubles..

Hi Samo,
Your 1960 40hp ought to be a "silent" style as both the Big Twin and Lark models had the package...
- Scott

 

[frustratedboater]

Re: Vintage Evinrude Block Troubles..

The 1955 25hp block is just about the same as the 1956 block. The difference in power comes from the change in piston and cylinder head design between 1955 and 1956, as they went from a 5:1 compression ratio to a 6:1 ratio. So, if you find a 1955 block, and can install 1956 30hp pistons with a 1956 head, you'll have a 30hp...

That said, if you are looking for a complete powerhead to just bolt on, a 1955 25hp powerhead will work (at 25hp, which you probably won't notice by seat-of-the-pants reckoning) as will the 1957 and 1958 standard 35hp powerheads (not the "silent" series ones).

- Scott

I really appreciate the great information. So correct me if I'm wrong, a 1954 25hp block will give me the same hp, if I use 30hp pistons in that block and the 30hp head as well? Are the bore dimensions the same? Just two more questions... Could I replace my damaged 30 block with a 1954, 25 block on my 30hp? Will everything bolt up evenly? Thanks for your help with this..
Ralph

 

[Chinewalker]

Re: Vintage Evinrude Block Troubles..

Hi Ralph,
Sort of. The 1954 block's bolt pattern to the mid may be different. The 1951 to 1954 Big Twins used a non-shock-mounted mid-section. The bolt pattern should be the same, but it may have a different studding pattern. You'd have to get them side-by side to see the differences. You could probably make it work, though... Yes, the bore dimensions are the same. The 1951-1955 25hp and the 1956 30hp are all 35.6 cubic inches.

My Dad used to say that the "hot" set-up for 36-class racing (1950s utility class that used the 35.6 cube Johnrudes) was to run the 1956 pistons/head in a 1954 model motor. Apparently, the 1954 model lower units had a slightly smaller cross-sectionional area which made them slightly more efficient. I guess when a half mile per hour makes all the difference, it is significant enough...
- Scott

 

[samo_ott]

Re: Vintage Evinrude Block Troubles..

Hi Samo,
Your 1960 40hp ought to be a "silent" style as both the Big Twin and Lark models had the package...
- Scott

Aha... Now I know what you mean and yes, all my 60's ones have it... It's just a hassle to remove to get inside.... thanks for the clarification. I'm not too fond of those 60's 40's anyway!