TOPIC: 56 Johnson 15HP(good first motor?)

OK, starting a new thread here as I'm sure I'll have some more Q's on this project. Last night I checked the compression after a little seafoam soak to loosen things up in the cylinders. Compression came out right about 92 on both cylinders, but I beleive I forgot to open the throttle plate all the way. Checked for spark, and seemed like only one lead was firing. Pulled the Manual starter off the flywheel, and through the flywheel window, I could see one of the coils is different than the other, so possibly one is still original and bad. Points were tight at.017, and I think the points and condernsers might have been replaced with the coil, obviously there has been some work done, as the engine has clear fuel lines as well, and I think tough up paint. I'm guessing over ten years back at least. I have a bunch of stuff ordered up with a carb rebuild kit, new lower seals and impeller, and coils points etc.. Also went ahead and ordered everything up for the Lark 2 which is coming into my shop as soon as this one is up and running.

Sark

Good deal! Take your time and have FUN!

Allright, recieved all my parts and got to work this weekend! Yesterday I pulled the flywheel and replaced all coils, condensors and points. The condensors were very loose and in one of the coils the needle looked rusty. Not to mention one coil was black and the other was blue, the blue one looked older and I suspect was part of the no spark problem on one cylinder.

Question on the spark plug leads. Do I need to cut them back a little so the new needles in the coil seat nicely making good contact or just put them back in(what I did)?

Also on reinstalling the flywheel, I was very careful aligning up the key, but it seems like the flywheel isn't perfectly straight level that I've mostly tighened it down, I think there is maybe 1/16" difference or a tad more ? Should I pull and redo, or just continue with torqueing it and it should level out?

Having fun and hoping to get to the carbs next.

Oh yeah one more thing, the spring washer under the armature plate, I didn't saee it in there but maybe I missed it, is that because this was used with a remote? Should one go back in if using a tiller? Help appreciated greatly!!

Ok, messed with the flywheel last night and I think it's the armature plate that is slightly off kilter, going to replace the spark plug leads(they are a bit crusty anyway) and reinstall everything hopefully level this time. Any tips or thoughs would be appreciated. Thanks.

Sorry I havent been able to log onto FG in a while .. THis am it finnaly worked! Sounds like you have made lots of progress and gotton good advice from others here. Hope all works out.
Jesse

Thanks, yeah lots of good avice so far and having a blast. Read from cover to cover cheap outboards over the past few days. I'm still working on the shift seal, I might try tapping it tonight. I Also need to pull the powerhead I guess due to a seal between the crankshaft and driveshaft being in poor shape. I was planning on practicing first on my frozen 57 18hp johnson that I grabbed for a couple parts(mainly the tiller).

Speaking of which is the lower end from the 18 compatible with my 15 hp 56? They look pretty similar, the 18 looks like maybe the cavitation plate is a tad bigger but it hould have same gearing no?

Planning on joining aomci next week.

Not sure.. never worked on either of those models... Some one should chime in. Sorry.

Ok finally back at this after getting sidetracked with way too many things.

I have rebuilt the carb,and magneto,changed impeller and lower unit oil.almost finished with a separate completely rebuilt lower unit as well. Had a heck of a time finding copper core spark plug wire, none of my local auto parts carried it. Everything is done now but I'm confused on where the flywheel should be when adjusting the points? Its it where it is marked top, or I have seen reference to the marks on the flywheel? Ready to test fire once I get this done and go through the two line tank. Also started on on Lark 40 HP, that one should be a breeze in comparison. Much better shape.

You can use the timing marks ( 2 vertical lines ) on the magplate and the 2 marks on the flywheel to " accurately " set the points using an ohmeter.--This gives you maximum spark intensity at the correct time.

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Having said that most folks just find where points are open the maximum amount and set them to 0.020" for good results.

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Both methods it does not matter where magneto plate is as the points are timed to the rotation of the magneto plate relative to the magnets and that is why it is called a magneto.

Thanks for chiming in! I found this video and then I understood why where the mag plate is doesn't matter. I just didn't get it without seeing it. You rotate the drive shaft! I was trying to do it by just rotating the mag plate/turning the throttle.

There is more than one video explaining how to use the timing marks for setting the points the best way possible.

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Results may vary as some video makers are better than others.

Copper core spark plug wire is easily found at the nearest lawn mower repair shop.

Those are some the best motors! Shot coils are the norm. Do new coils, etc, and with solid internals will last for decades!

On the compression check a 2 stroke, there is no need to open the throttle plate. When a 2 stroke is going to BDC, exhaust port is open to atmospheric pressure, so with the throttle plate open or not, still the same the up stroke.

On a 4 stroke, yes on open plate as it has valves.

And 90+PSI is great! Seen great runners with 60!

Wow that was much easier. Thanks for the tips professor. Got me going in the right direction and once I saw them rotate the shaft in the video what you said made total sense. I knew I was misunderstanding something. Can't wait to fire this bad boy up and see what happens. Hopefully this weekend.

I ordered a lower unit seal kit from sierra but it seems it has everything except the prop shaft oil seal. Not sure if I ordered wrong thing or what?

Glad to see you made progress! I got sidetracked as well! Good Luck this weekend!

Making me miss the 1957 Johnson 18 I rebuilt a few years ago...it was a great runner.

Enjoy!

nice Triumph on the bench built a few but a lot of Harleys
Charles

Thanks Charles, I built a few brit bobbers back in the early part of the millenium, when they were hot. The craze died off. This was my favorite.

Might recognize the short Sporty front end and Dyna rear wheel....

Bernie

I'm back, still haven't fired this guy up. Didn't really get into my wrenching mode last winter.... This year it's a priority, my father in law past this year and I really want to complete some of the motors he gathered through the years but never worked on. This was the first one, still need to get the new plug wire and that's it. Anyway hoping to wrench on a great condition Lark next that should just need the basics- Then a fisherman that is beautiful but I think is burned up based on the discoloration on the exhaust cover. Might grab one or two other johnnyrudes from the stack before we sell what's left off if something pops out at me, but I don't have a ton of room and have a bunch of big white mercs I know I want a poke at someday.