Correct Crankshaft for 1956 RDE-18

[olcah]

I want to replace the crankshaft on a 1956 Johnson RD-18 30 HP. The crankshaft part number for 1954 and previous Big Twins is 302530. For 1957 and later years the crankshaft number is the same 302530. For 1955 and 1956 it is 203655. The only difference I know is that some of the 1955 and 1956 motors had a lip seal on the lower crankshaft in place of the carbon seal used in 1954 and 1957. I figured the 203655 would only take the lip seal so I should go with 302530. But..when I look at the original 1955 and 1956 parts lists and drawings they show the carbon seal at the bottom crank bearing. I definitely want the carbon seal at the lower crank bearing.

I have located a NOS 203655 and don’t know if I should purchase it.
Does anyone know what the difference is between 302530 and 203655? Frank can you help?

[wyo307]

I think you should be good because on those motors with the bad lower crank shaft seal (like my 1955 RDE-17) you can replace that bad lower lip seal #303804 with the good seal #321467 or sierra #18-2060 and they fit on the same crank shaft just fine. I just did this on my RDE.

[frankr]

Crank is the same with either seal type. Bearing is different, according to seal. When I get back from an appointment, I’ll see if I can figure out the part number question. Could be related to the rod bearing rollers or cages or flywheel key, or?

[chris-p]

The 203655 can be used in the following:

THE RD SERIES MOTORS:
RD-10 through RD-19C, RDE-16 through RDE-19C

The RJE SERIES MOTORS:
RJE-18, RJE-18E, RJE-18C, and RJE-19

[chris-p]

I just restored 2 ’56 30hp powerheads and put 302530 cranks in both of them. Thing is, I cannot remember if I swapped in different connecting rods when doing this. As we know, you can always use superseded numbers, but you cannot always go BACKWARDS with them in years.

For Rods, the following is true:

RD-10 through RD-17R, RDE-16 through RDE-17R use the 375767 Rod (These are the 25hp Motors)

Then the….

RD, RDE, RJE 18 through 19C, RDS-20, RD-21, and RDS-21 use the 377272 Rod (These are the 30and 35hp motors)

So I think, while sitting here eating my dinner, that you can swap the 302530 crank between any of the 25/30/35hp motors, but if you use it on the 25hp, you may also need to swap out the connecting rods as well. Just my initial guess. After I eat ill go down and actually look at the parts.

[olcah]

I will check to see condition of the NOS 203655 crankshaft. Frank, Chris and Wyo thank you for your help with this. It is much appreciated.

[ADAM GIBB]

I was researching your question, and I think I may have solved my problem mentioned in a previous post at the same time.
viewtopic.php?f=5&t=6136&p=31387#p31387

I was having trouble with getting the flywheel to sit down correctly on an RD17. It seems that the 203655 crank came into use in 1955, was used in 1956 and then went away, as they switch back to the 302530. This coincided with the changes in the seals. The RD series up until 1954 had carbon seals with the washers and springs to hold them in place. Part way into 1955 production, the switched the top and bottom bearings to one that had an integral lip seal. This is where all of the issues with water getting to the lower bearings came from. At some point during 1956 production, they went back to the carbon seal on the bottom end of the crank, and left the lip seal on the top, where there is no water to worry about.

So…..after looking through all of my parts books, I find that the 203655 crank was only ever used with the lip seal on the top end. I have not see a parts list that shows that crank with the carbon seal on the top end. I believe that the cranks are completely interchangeable, as long as you use a top bearing with integral seal.

I think this must be the underlying cause of my problem in the post mentioned above. I may have put a 203655 crank in the engine, and used a top bearing that requires the external seal. Before I tear down the power head again, I will try to get dimensions of of a known 203655 crank and measure one of the 302530s in the junk box and see if the shoulder at the top is in a different place. I think it is…..any want some lightly used gaskets LOL.

I also wonder why they would have changed the crank at all. It seems they could have stayed with the 302530 all along.
Hope this helps.

[olcah]

I should receive a NOS 203655 crank within a couple of weeks. If you identify the dimensions that you want I will get them. I also have a damaged 1954 Evinrude (302530) crank to compare. Looks like you may have solved the question. Thank you.

[frankr]

OK, I just went through a bunch of parts books, and found the numbers for the crank for a variety of years and models. What I found is that 203655 replaces 302530 for any year, without regard to seals or bearings, etc. As always, that doesn’t mean that 302530 will always replace 203655 (backwards compatibility). Note that 302530 kept showing up as late as 1957 (but superseded by 203655).

Conclusion: Now I have to dig back into my brain’s memory bank. I remember that somewhere along the line, the lower seal area started being chrome plated so the carbon seal wouldn’t rust to the shaft and fail to move up and down as the crank moved up and down within it’s end play limits. I think that probably is the difference between 302530 and 203655. Could be mistaken.

Whew!!

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[olcah]

Frank, Thank you the research. Lots of great info in your table.
Charlie

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