Topic: 1956 Johnson 30hp Rebuild – Antique Outboard Motor Club,Inc

This topic has 20 replies, 7 voices, and was last updated 2 years, 11 months ago by bobw.

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May 12, 2021 at 1:32 pm #238233
bobw
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I’m rebuilding the powerhead on a 1956 Johnson 30hp and had a few questions:

1. As long is I have torn open, I’d like to avoid the 1956 rod bearing problem and upgrade the connecting rods to the later #377272 rods with the better small end bearings. Will this change require a different wrist pin and/or piston as well?

2. My parts list does not show an O-ring on the upper crank bearing. But there is an O-ring type groove in the crankcase and during dismantle, I found an O-ring had been installed on the upper bearing at some point in the past. O-ring required or no? I know that some motors used an oil recirc system that did not use an O-ring on the upper bearing – there appears to be an oil return hole in the groove, so wanted to verify what is correct here.

3. During the dismantle process, I failed to notice the orientation of the upper crankshaft thrust washer. I assume the bronze side of the washer faces down towards the crankcase? See pic.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."
May 13, 2021 at 2:25 pm #238278
fleetwin
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US Member - 2 Years
Did the powerhead appear as though it was split apart before you? Yes, the groove is right there inviting you to install an oring, but don’t if the parts book doesn’t show one…I don’t have access to a 56 book, so can’t say for sure…I’m sure someone with more knowledge will chime in…
May 13, 2021 at 2:52 pm #238280
bobw
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US Member
Fleetwin – appreciate the response. Can’t say whether or not it had been opened up before I got it. This is the bad powerhead I reported on a couple years ago – I picked the motor up from some guy who left it laying on the ground out in the weather for about 20 years and it was rusted up solid. The basic block/crankcase and one piston are good, the rest will all be replaced as part of this rebuild.

After posting my inquiry above, I did verify in the Johnson service manual that this was a powerhead with a later revision that added an oil recirc hole in the groove and deleted the O-ring on the upper bearing. I cleaned out the oil passage to ensure a clear return, and it will get reassembled without the O-ring. Don’t know whether the O-ring I found was just a factory oversight or if someone else had been in there before me and didn’t know.

If anybody can help with my con rod question, it would be appreciated. I have a chance to pick up 2 of the later rods (and NOS) at a good price.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."
May 13, 2021 at 3:53 pm #238284
olcah
Participant
US Member
Bob,

https://www.aomci.org/forums/topic/1955-25-hp-johnson-loose-conn-rod-bushings/

In the above thread Garry in Michigan said that the specs for the wrist pin bearings changed during production in 1956 :

” The suppliers specifications changed and the new bearings had the same part number but were better quality. The only ’56 early serial number Big Twins that you would find with bad wrist pins today would be in an old dealers back room still in the sealed factory box.”

If I misinterpreted his words I welcome correction but in the meantime I am hanging my hat on this and so far I have had no rod bearing problems on any of my three RD18s.

Hope this helps.
May 13, 2021 at 4:20 pm #238287
bobw
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US Member
Ok sounds like the 377272 rod will work with what I have.

Edit – the serial number welch plug is missing on this powerhead so I have no idea where it fell in the production run. Based on the last comment by Dan in the referenced thread, it sounds like the 377272 rod will work. I’ll order one and find out – I’m told it can be returned if no workee.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."
- This reply was modified 2 years, 11 months ago by bobw.
May 13, 2021 at 7:36 pm #238302
olcah
Participant
US Member
That makes sense in a rebuild situation. Please let us know how it works. It would be good knowledge for all who work on RD18s.
May 13, 2021 at 9:47 pm #238318
bobw
Participant
US Member
olcah wrote:

That makes sense in a rebuild situation. Please let us know how it works. It would be good knowledge for all who work on RD18s.

Olcah – will post a follow-up note next week after the new rod arrives. The crankshaft and big end bearings are the same between the ’56 30hp and the ’58 35hp so just need to verify the ’56 and ’58 wrist pins are the same diameter. Obviously, the ’58 wrist pin is longer with the larger bore cylinders but I’m thinking the diameter should be the same. I like the idea of one large roller bearing on the ’58 small end as opposed to the two smaller bearings on the ’56. Best of all, I managed to find 2 NOS ’58 rods that were half the price of a few used ’56 rods so hope they work.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."
May 14, 2021 at 7:52 am #238334
stanley
Participant
US Member - 2 Years
Getting back to your O-ring question,the change came in the 1954 model year,I think.On the earlier 25hp RDs,the thing to look for,besides the hole in the groove, is a small hole in the reed plate which indicates no O ring is necessary.I assume the 1955 model would also have that hole,unless someone swapped in an earlier reed plate and the O ring you found.
- This reply was modified 2 years, 11 months ago by stanley.
May 14, 2021 at 9:03 am #238343
bobw
Participant
US Member
After reading the service manual regarding the recirc system, I verified the reed plate does have the small oil recirc hole as well. Based on that, still don’t know how or why somebody had previously installed an O-ring on the bearing.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."
May 14, 2021 at 10:31 am #238350
olcah
Participant
US Member
I found a 1954 Johnson RD that had both the updated drain system and the oring. The parts list for 1952 RD 12 shows the oring while the 1956 RD18 PL does not. I think that people just assumed that an oring was required and put it in. As you saw the Johnson tech manual to 1964 page 308 describes backfitting the drain system and deleting the oring.
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1956 Johnson 30hp Rebuild

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