Topic: 1929 Johnson A-45, 3 hp – Antique Outboard Motor Club,Inc

This topic has 7 replies, 4 voices, and was last updated 1 month, 2 weeks ago by Buccaneer.

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September 20, 2026 at 5:09 pm #328810
Buccaneer
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I guess it ran fair for being a 97-year-old motor.
The fuel adjustment needle is “touchy”.
Before the video it backfired so hard it blew the
core-plug out of the front of the carb!
Anyone had that happen before?
Luckily, it landed in the boat.
To make matters worse, when it backfired, it would slam the throttle
spool to “Choke”. After the first time, I was quick enough to “un-choke”
it before it died.

It seems to run better at slower speeds, and sometimes it seems to have
an ignition “miss” at high speed.
It got me “there”, and then “back”, so I’ll give it a “B”.

VIDEO….
https://youtu.be/XIU9xpwmU5A

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September 20, 2026 at 10:58 pm #328844
Tubs
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Did you leave the backfire suppressors in or were they breaking up like the ones in this motor. They say you don’t need them and you should take them out as the pieces can end up in the crankcase. The one with the arrow pointing at almost made it. I believe that its the backfire that breaks them up. I’ve run 2 Johnson’s with this power head and find the mixture touchy as well so its easy to get to the lean side and – BANG!!!

A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.
September 21, 2026 at 8:26 am #328860
GARY
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I have several A45s and run them all.One thing common to them all is that the compression relief valves have all leaked.That plus the fact that there are no crankshaft seals,means that the more use the motor has had,the harder it is to get it properly tuned.I don’t know that’s your problem,but something to consider.
September 21, 2026 at 8:43 am #328861
Buccaneer
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Gary, thanks for the input.
I did remove the compression release assembly
and lapped the valve, which was in good order.
Compression is seemingly good, and no side-play
in the flywheel, but other than that, she’s not
revealing her past.

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September 21, 2026 at 8:48 am #328862
Buccaneer
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Tubs, good point on the baffles.
I didn’t “open up” this motor, and it was,
at least cosmetically, gone through in the past,
and it looked like it was pretty much ready to go.

I have ran into those deteriorated baffles in the past,
perhaps on my other A-45. Perhaps I’ll add it to
my winter’s “To-Do” list to check them.

Thanks!

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September 21, 2026 at 11:52 am #328867
GARY
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You’re an old hand and I’m sure you’ll figure it out.
September 21, 2026 at 12:10 pm #328868
JOSEPH BRINCAT
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I never had an appreciation for the backfire suppression screens until I happened to be reading an old book about two cycle marine engines. Looking at the section drawings and descriptions for the various two port 2 cycle engines they all seem to have baffle screens in the by-pass passages to prevent firing into the crankcase. … just saying !

Joe B
September 21, 2026 at 3:57 pm #328875
Buccaneer
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JOSEPH BRINCAT wrote:

I never had an appreciation for the backfire suppression screens until I happened to be reading an old book about two cycle marine engines. Looking at the section drawings and descriptions for the various two port 2 cycle engines they all seem to have baffle screens in the by-pass passages to prevent firing into the crankcase. … just saying !

Joe B

Maybe that core plug it blew out of the carb was the Relief Valve!

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