Johnson power head ID

[Buccaneer]

In a box of outboard parts I bought there is a
twin cylinder, maroon Johnson power head. Guessing it’s
in the 18 hp + range.
I find no numbers on the core plug, etc., that would indicate
a model year. I did find two parts #’s…….
552213, upper by-pass cover
308361, bracket of some kind on port side.
While Marineengine.com did find the parts numbers, it
doesn’t tell me what they fit.
Any clues on the Year and HP?
Thanks!

Prepare to be boarded!

[billw]

I would start by seeing what socket size fits the head bolts if you’re really not sure. 7/16" would be 10 hp and below, I believe. 1/2" would start at 15 and go up…..Maroon, if original paint should be 1956 to 1958. I’m sure someone will zap me quickly if this is wrong.

Also, the 18 hp. top two head bolts are 2.0 inches apart, center-to-center.

Long live American manufacturing!

[fleetwin]

Those numbers could very well just be "casting numbers" which are meaningless to most of us unless you had access to engineering records/software.
The maroon color would indicate that the powerhead is from a 1956-58 engine, unless it has been repainted. You mention that there is a core plug, are you referring to the ID plug on the right side of the block? If so, it is very strange that the core plug has no numbers on it.
Post a picture of the powerhead so we can get a better idea of what you have.

[Buccaneer]

Both the numbers showed up on Marine engine as "parts",
and the one said "by-pass" cover, the other just said NLA.
I’ll check out the head bolts tomorrow.
The maroon paint looks original. The core plugs just
had a couple of letters on them, perhaps MD or similar,
probably the manufacturer name…… perhaps they’ve
been replaced.
Will take a photo tomorrow!
Thanks!

Prepare to be boarded!

[Buccaneer]

I check out the Johnson power head. It must be
an 18 hp as the headbolts 5/16", and the top
two are 2" apart.
The core plug has the letter "M" and RPH on it.

On parts diagrams, for 1956 I see (4) versions of 15 hp FD10 models listed.
For 1957 there are (4) 18 hp FD11 versions.
For 1958 there are (4) FD12 18 hp versions.

Any easy way to narrow it down with the photos?
Thanks.

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Attachments:

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[fleetwin]

OK, what you have there is either an replacement powerhead, or a replacement crankcase, the color is close to the colors used from 56-58, but this is a 60s model FD 18hp. The thermostat and lack of pressure nipple on the intake manifold. So, I’m thinking this was used on a 1960-66 FD 18hp. I’m basing this year range by the white paint on the parts swapped over from the original powerhead.

[ede]

Paint looks like red primer

[fleetwin]

quote ede:

Paint looks like red primer

Yes, you are right, that is the primer not a coat of paint.

[chris-p]

yeah, I would say that is a factory replacement powerhead that never got painted, 60s vintage. cool score. Might have low hours on it.

[Buccaneer]

Thanks for the replies. It looked maroon to me in the
garage, but will have to take it outside in the natural
light to tell if it’s red primer.
I guess the impulse port on the upper by-pass cover
normally dates a Johnson after 19 __?
Looks like a touch of blue on the head…… perhaps
a true morphadite?
I’ll try looking at some of the 60’s diagrams.
Thanks!

Prepare to be boarded!

[Author]

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