Expert Diagnosis: Expertise genuinely appreciated

[rschrull]

Will post after this is approved youtube video links.  Have a Johnson RD-17 (1955 Johnson 25 HP “Big Twin). Just had an experienced fellow vintage outboard motor mechanic (Bobby Johnson) tune the motor. Did a super and knowledgeable job.  He could not at the moment help further, re what you are seeing in the first video (happened exactly the same in his tank).  It looks like a sneeze, however, notice at once instance (very short moment in the second video) where a tiny puff of white seems to come out from under the ignition plate. Notice in the first video, it’s like it’s sneezing.  When in the lake, under power, it’s even more pronounced. Can get up to speed, as it jerks too hard.  Going to test the area by first spraying something like WD in the area and see if it changes the sound, but also Dawn dishwashing to see if it bubbles anywhere.  Will do these tests this Friday. Wondering if anyone experienced here might have an idea of what is going on. Top crankcase seal is fine. No idea re the lower one, but again, the puff seems to be coming from and area just below the ignition plate and close to the crankcase.  Any guidance/ideas here would be most appreciated.  Having spent all summer restoring a Tee Nee trailer and the boat, very much desire to get this puppy running.  Thanks in advance…..

[rschrull]

https://www.youtube.com/shorts/Co47g5Iygjw

[rschrull]

https://www.youtube.com/shorts/3cqgMQO31O8

[PM T2]

The clutch dog is slipping which is a sign either it or the shoulder on the inner hub of the gear is worn., the “sneeze” is actually the gear quickly disengaging then catching again as the parts rotate. You might be able to fix it by flipping the gears around from front to back. You’ll have to disassemble the lower unit to find out.

To be honest, your motor doesn’t even SOUND good in the video, it almost sounds  to me like its only running on one cylinder. Maybe its just how the camera makes it sound. At any rate, what I see is that the white smoke isn’t really coming from under the mag plate, its exhaust smoke/steam being recirculated from the back to the front. Maybe there’s a leaky hose or or seal or fitting somewhere, because either there’s an air leak or  the mixture needle needs to be fattened up a little. Just my deux centavos.

PM T2

He's livin' in his own private Idaho..... I hope to go out quietly in my sleep, like my grand-dad did..... and not screaming, like the passengers in his car...

1 user thanked author for this post.

rschrull

[rschrull]

Thanks PMT2, Another person shared that also. And yes re the running on only 1 cylinder. It likely was in the video. Since then Bobby Johnson worked on the ignition and we solved that issue, but not the bump/sneeze like thing.  This might seem off, but would it make sense so as to definitively determine, to first remove the prop and run it engaged, so see if it stops doing the bump thing simply because there is no strong load, the prop having been removed….., or just take the time to remove the lower unit and check the clutch dog?  You know, what I would REALLY like is to learn about these motors alongside someone who has worked on them for years. I’d love the learning. Heck, I’d drive a couple of hundred miles to be able to spend a few days leaning into something like this, perhaps more for the learning than the fix. Wish I could link up with someone who wants to pass along the knowledge. Here is something else that might be important? In that second video, the skip/sneeze or whatever it is, happens but in that video the engine is not engaged/in gear in forward. So it’s doing this even in neutral. Would that point to it not the dog and something else?

 

[JACQUES]

to understand and service your oldy the johnson bible is free for download   450 pages covers everything you need .i will send you the link later today as i no access to my home pc now.

 

in the mean time…

Magazine Articles | Western Reserve Chapter

found  it with chat..

johnson_service_manual_10th_edition.pdf

 

Joining AOMCI has priviledges 🙂

1 user thanked author for this post.

rschrull

[Tubs]

.

A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.

1 user thanked author for this post.

rschrull

[rschrull]

Thanks Tubs. I did in the original post (Bobby Johnson tuned the motor but did not go further and note that what happened in the video also happened in his tank). Reading carefully the post, one would usually conclude the running on one cylinder is solved. Post question was focused on what the tump/jerk is. But anyway, turns out it is not the clutch dog. Removed. It’s fine. All lower unit checks out with little to no play anywhere. No worn gears, or metal in the gear oil. Ignition absolutely perfect thanks to Bobby. Other things done. Packers replaced. Carb is service/checked and fine. Bobby adjusted the low and high speed in his tank under and in gear, although not on the water, so should be a final adjustment under power as I have done with another boat and motor I have. This is entirely something different and all I’ve been able to research points to some kind of leak in the crankcase. But the internet, reddit posts and FB groups isn’t the best place to research this kind of stuff. It’s like the wild west. That’s why I’m here on this forum, as I’m told experience resides here.  “AI (Claude) research concludes that because there is no change in RPM when this occurs, a clutch skip can’t happen without the engine briefly losing its load. That if the prop shaft disconnects, even for a fraction of a second, the engine always reacts to that with a momentary flare. Flat RPM through the clunk means drive was never interrupted. Whatever is banging, it’s downstream or outside the driveline.  I don’t buy it, my gut is, that it is upstream in the powerhead.  Maybe this forum isn’t the place to resolve this challenge? I openly wonder. Perhaps the ideal place is to be side by side with an older someone who has lived with these engines and is willing to and earnestly desires to take the time to go through it all with someone new to the engines, to pass on what they have learned over the years, while at the same time fixing the problem.

 

[Don]

Watched both videos.  The engine is jumping out of gear in the first video.  You better get that gearcase back off and check the shift rod connector.  Recheck the fine adjustment on the shift handle as well.  Continued running like this will do permanent damage to the clutch dog and gear lugs, if it is not too later already..

The second video shows that you are pushing the carb butterfly open without advancing the throttle/timing….  This will normally created a  lean condition and a lean spit, so perhaps there is nothing wrong.    The puff coming under the mag plate is from the excess pressure caused by the back/fire lean spit.  The pressure may be more than the upper seal can handle….

1 user thanked author for this post.

rschrull

[rschrull]

JACQUES wrote:

to understand and service your oldy the johnson bible is free for download   450 pages covers everything you need .i will send you the link later today as i no access to my home pc now.

 

in the mean time…

Magazine Articles | Western Reserve Chapter

found  it with chat..

johnson_service_manual_10th_edition.pdf

 

Thanks Jacques. Those are great resources. Downloaded the manual. Lots within it and pictures one can actually see clearly, (compared to SELOC manual). Thanks again.

[Author]

Posts