Johnson TD 20 fuel tanks

[Stickler]

Hey guys, i recently purchased 2 TD20 johnsons and just noticed that the tanks look the same but have one major difference, one tank has a seam that runs around the whole perimeter,and the other one is seamless, any thoughts?

 

[Stickler]

I'm just curious as to why the tanks have this difference since they are both td20, did the tanks change between years?

 

[F_R]

That was a design change when the went from a cast aluminum tank with seam to a sheet aluminum tank. I think the cast one was a left-over from the pre-war models. It took them awhile to get back into full swing of things when the war ended and they did whatever they had to do to get back into production.

 

[Stickler]

thanks for the info, are there any pros/cons to either tank, other than the seam, I guess what I'm wondering is if they may be more likely to leak from the seam area.
One other thing I noticed is the cast tank with the seam is quite a bit thicker, doesn't sound as hollow when you flick it on the side.

 

[F_R]

The cast one is thicker. A lot thicker. And that is the "pro". You will never see a dented one unless it got ran over by a semi. If there are any "cons" it would be possible leakage at the seam (rare but hey it is 70 years old). And heavier in weight.

 

[Stickler]

Thanks for the insight F_R, was also wondering if the color of these motors were the sea mist green, or may have changed between years, is there a serial number list available to pinpoint the years they were made?

 

[F_R]

Yes there is, in "The Old Outboard Book" by Peter Hunn. Post the numbers and I'll look them up for you. Or of course, you can buy the book for lots of interesting reading.

 

[Stickler]

The numbers are 60716 and 68459, thanks!

 

[Stickler]

Was also wondering if anyone has a pdf manual they would be willing to share with me?

 

[F_R]

Those numbers can't be right. Those would be 1927 and 1928. An example would be a 1949 ranges from 698,875 to 787,023. 1946 range is 491,737 to 538,800

 

[Chinewalker]

I believe those are Peterboro Johnsons, which would explain the serial numbers.

 

[F_R]

Yeah, I thought of that after I wrote that. I have no info on Canadian numbers.

 

[TN-25]

The TD-20 was the start of the streamliner motor styling for 1941. Pre-war they were dull aluminum in color, then post war they were painted in the light green known as Seamist Green. That color continued through 1951, then they switched to a slightly deeper green known as Sea Horse Green for 1952. They used it through 1955, 2 years into the TN replacement motor production, the 5? horse "CD" motors.