RDE-17 Johnson tuning issues

[chris-p]

No installing the boss gasket will cause no ill effects.

It is primarily used on fixed high speed jet motors. However, I install it in all of the carbs I service.

[Buccaneer]

Thanks Chris, good to know about the boss gasket.
I just tried test running the motor again, and
while it did "lean sneeze" at first, after I got it
running steady for a few seconds, it sounds like it has
a "spark" knock. Took a video, and am uploading now.
If I get time before my son shows up for boating,
I’ll add it.

quote Chris_P:

No installing the boss gasket will cause no ill effects.

It is primarily used on fixed high speed jet motors. However, I install it in all of the carbs I service.

Prepare to be boarded!

[fisherman6]

Buc, If you out a boss gasket in the carb, your initial setting will have to be farther out than 1/3 turn. There is not a problem with putting one in and I always do. They did not come with one though. The thought was that the fuel consumption was sufficient that proper adjustment could still be achieved without it. Since you put one in, start with that high speed needle 1 turn out. It will be rich, but you will be able to tune it right in.
-Ben

OldJohnnyRude on YouTube

[Buccaneer]

Ben, that’s what I "thought" would be needed with the boss gasket installed,
so I opened it up about 1-1/4 open. After the last run, and my previous
post say I think there is a ignition miss, I was tightening some screws
on the crankcase covers and noticed a little piece of copper wire laying
in the pan. You can tell that it’s been flattened by as screw, so it made
me think "magneto". Perhaps a wire broke inside. Anyway, while
I was out "boating", my video finally uploaded.
What do you guys think?
https://youtu.be/UEAIxP8Di10

quote Fisherman6:

Buc, If you out a boss gasket in the carb, your initial setting will have to be farther out than 1/3 turn. There is not a problem with putting one in and I always do. They did not come with one though. The thought was that the fuel consumption was sufficient that proper adjustment could still be achieved without it. Since you put one in, start with that high speed needle 1 turn out. It will be rich, but you will be able to tune it right in.
-Ben

Prepare to be boarded!

[outbdnut2]

That does sound like a lean sneeze, but you had a fast idle going so maybe you were in an area where it was starting to transition from the low speed to the hi speed jet and none of the RDs run smooth at that throttle setting, especially when cold. I’d first try backing the throttle off a tad so you are definitely fully on the low speed needle, then turn it richer and see if the sneezing stops. At the point where sneezing just stops, turn the low speed needle 1/4 turn richer, but do this again with it fully warmed up for your best setting – when done this way, it may still sneeze while warming up unless you leave the choke part way on. Note that most of these RDs (25 to 40 HP), when properly adjusted, will still sneeze at an idle when first started up cold, but that should stop as it warms up. I have about a dozen of these motors, and so far have worked over 4 of them to good running condition. It doesn’t take much of an RPM increase from slow idle to get some gas going in the high speed venturi, and if you have that happening, you will never get a good low speed needle setting. I also put a boss gasket in all of them if they didn’t have one – and, as has been mentioned, the hi speed adjustment has to be made richer. I’m sure you already know that the low speed gas goes up a passage on the side of the carb bowl to the low speed needle above the bowl – spraying carb cleaner through this passage insures it is unobstructed.
Dave

[Buccaneer]

Thanks Dave, I won’t have much time tomorrow to work on it, but
I may pop the flywheel back off just to satisfy my curiosity and
make sure a wire on the mag plate didn’t break or get ripped off.
It’s kind of aggravating trying to tune an outboard when
you can’t even put it in gear to warm it up!

Prepare to be boarded!

[outbdnut2]

quote Buccaneer:

Thanks Dave, I won’t have much time tomorrow to work on it, but
I may pop the flywheel back off just to satisfy my curiosity and
make sure a wire on the mag plate didn’t break or get ripped off.
It’s kind of aggravating trying to tune an outboard when
you can’t even put it in gear to warm it up!

I worked on a ’59 35 HP Lark today that killed when I put it in gear and gave it any throttle at all above idle on a boat. Had it idling good in a tank, and idled good on the boat at low RPMs. Had to readjust the points a couple times to get it to idle good – maybe because I used Sierra points. After that, the culprit was the hi speed jet was set too lean. I found that by trial and error, restarting several times. The high speed adjustment is very touchy on these and sometimes if you are off 1/8 turn, they run terrible.
Good Luck!
Dave

[Buccaneer]

I remember when I tore the carb apart, looking at the HS needle, thinking,
"what happened to the point on it"! After seeing the needle, I can understand
why they’d be "touchy" to adjust.

Have a couple of hours to "play" this morning, so I popped the flywheel back
off. I see absolutely no sign of anything broke, loose, or arcing.

Had the thought a while ago that I should have disabled the "high speed cut-out".
The only test I did on it was via an ohm meter and "mouth" for suction,
and it would easily close the contact.
Could this cut-out switch cause my symptoms?

Also had regrets this morning that I didn’t pull off the front cover
and inspect the reeds. There again, would a reed issue
match the symptoms in my video?

I have the flywheel off yet, should I keep tearing things back apart,
check the reeds, re-visit the carb, etc., before test starting / running again?
What would be your approach be…….. now?
I know you old wise men with whiskers, achy joints, and greasy fingernails
would have checked "everything" when it was apart the "first" time, lol.

quote :

I worked on a ’59 35 HP Lark today that killed when I put it in gear and gave it any throttle at all above idle on a boat. Had it idling good in a tank, and idled good on the boat at low RPMs. Had to readjust the points a couple times to get it to idle good – maybe because I used Sierra points. After that, the culprit was the hi speed jet was set too lean. I found that by trial and error, restarting several times. The high speed adjustment is very touchy on these and sometimes if you are off 1/8 turn, they run terrible.
Good Luck!
Dave

Prepare to be boarded!

[outbdnut2]

I ran your video again, and I think your problem is carb-related because you had a few seconds of smooth running before it coughed and quit. First, I’d back down to a slower idle and see if you can get it to run smooth by adjusting the idle needle. Next thing I’d try is setting the high speed needle richer in 1/8 or 1/16th turn steps. If you do this and find a spot where it doesn’t die at throttle setting somewhere above slow idle, even though it may cough, then I’d put in on a boat and further adjust the high speed needle. You will also find that changing the idle needle a bit may mean readjusting the high speed needle because quite a bit of gas is sucked through the low speed passage when running at high speeds.
I don’t think it’s reeds because it ran smooth for a few seconds.

You may also see if it stays running with the choke part way on – this also tells you the high speed knob needs to go richer.
Don’t ever expect really smooth running just above idle speed, especially with a cold motor – it’s the way all the RDs I’ve had are – you can get smooth running a bit above idle by turning the idle needle richer, but then it probably won’t slow idle good when warmed up.

Another thought – I’m wondering if your tank is getting pressurized enough to keep the carb full? Will it stay running if you keep pumping the tank primer?
Dave

[garry-in-michigan]

I know I have answered this question before – In the 1950s when these classics were build, it was thought that the percentage of the fuel that could bypass the high speed needle valve through this route was so small that it could easily be compensated for with a fractional turn of the adjustment knob. Since this percentage grew as the outboards demand for fuel decreased, the smaller motors required that the small gap at the junction of the upper and lower carburetor castings be sealed. This changed with the introduction of the fixed jet carburetors. This reduced the number of complaints from people with misadjusted carburetors while increasing the numbers of motors damaged from running too lean. For those who trusted themselves more than they trusted the engineers, a kit was offered for the high speed needle valve. These were a necessity for motors used at differing altitudes. . . 😎

[Author]

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