Backfiring

[tpls63]

I need some more help with my 1956 Johnson 30 RDE18C.
I bought this boat/motor 6 years ago and at that time I purchased and installed new coils, points and condensers and fired it up but never really ran it. I parked it as I planned on restoring the boat someday. Well I've completed the boat and now I'm trying to get the motor running. I rebuilt the carburetor.
It fires good but also back fires and I can't get it to run at start or slow. There is a good ground through the mercury switch all the way to the slow position on the throttle. If I start it in gear with the throttle open a little more it starts and runs but misses.
I checked the point gaps and they're good and from the info I found on here the timing looks good as the scribe mark on the flywheel lines up with the mark on the brass piece behind that rubber wheel.
Any Ideas on what I'm missing or how to make it run slow?
Also there is a wire bundled up under the carb and the other end goes to one of the points. I imagine that was someones kill switch at one time?
Thanks again for your help!!

 

[RCO]

Sounds like you need to go through the carb again. The "backfiring" is probably a lean sneeze. The mercury switch has no bearing on how the engine runs. Don't worry about timing, just verify that the points are set at .020. The wire from the points sounds like it was hooked to a kill switch at some point, there should be a wire from the other set of points going to the vacuum switch which is where the other kill switch wire would be connected.

 

[tpls63]

Would it just be a matter of opening the slow speed screw more? The only thing i did in the carb is a new float and inlet valve

 

[tomhath]

Does sound like it isn't getting enough fuel. Float height might be too low, weak fuel pump going bad, or you need to open the low speed needle.

 

[F_R]

Mark on flywheel lines up with mark on brass cam??? Nah, that has nothing to do with anything. Look to the left of that rubber roller and you will see a pointer sticking up from the intake manifold. When the mark on the brass cam is aligned with that pointer, the roller should just barely be ready to start opening the carburetor shaft.

Open the slow speed needle 1-1/2 turns as a beginning point and adjust from there at idle.

Somebody has added that yellow wire for a kill switch. I notice it is laying on top of the moving points arm. May eventually wear through the insulation.

 

[tpls63]

I'm away til Wed so I'll remove that yellow wire then, check that pointer alignment and try adjusting the low speed screw and hope I get it to run. My book says to start with low speed screw one turn out so opening it more will probably help. Ill let you know, thanks!

 

[oldboat1]

Check to be sure the plug wires aren't crossed top to bottom. Usually a little brass reminder clip on the top wire, but might have been removed.

 

[tpls63]

The plug identifier is in place and on the right plug. First thing I thought of too.

 

[oldboat1]

Will add a point or two in case you haven't got it up and working yet. It looks like your link and sync might need adjustment -- wheel should contact cam at the line, not before it (engine runs at low or low-to-med idle without the wheel making contact with the cam). Additionally, I think I would disconnect any kill wires until you get it running right, just in case there is some ignition interference there.

Are you pretty good at carb rebuilds? Based on the pic, it looks like the domed plug at the top might not have been removed recently. I disassemble internals and soak everything metal (incl housing tops and bottoms), then poke around with small wire and finish with carb spray. That includes the idle passages up at the top, and the nozzle that runs up vertically in the middle of the carb. There should be a gasket at the bottom of the nozzle, most models anyway. Like the small holes up at the top under the plug, the holes in the nozzle usually have to be cleaned out with fine wire and sprayed out with carb spray.

Initial needle setting are 1 1/2 out for the idle mix, and 3/4 for the h.s. mix. Also, I'm pretty sure your model should have a throttle stop screw down at the bottom of the throttle tower (where the mercury switch is) -- plastic screw and spring. It's not absolutely necessary, but useful.

(Apologies if this is old stuff for you.)

 

[tpls63]

oldboat1 thanks for that. It's never old stuff for me, I always appreciate input. I'll double check everything before I try to start it again. Thanks again!

 

[tpls63]

Well I got it running and took it out in the water last Saturday. Gave a bunch or relatives rides and let the grand kids all drive it. It ran great for 2-3 hours and then all of a sudden some metallic clunking noise, I headed for the dock and about 100 ft short of the dock it locked up. Stuck tight now and won't turn over. It's in the power head, not the gear case.
Might have broken a rod or something like that to lock tight. Are hard internal engine parts available anywhere for these old motors? I'm thinking maybe a rod, rod and crank bearings, rings and seals.
Here's a short video of it running: https://youtu.be/OS5HGgK6qI0

 

[oldboat1]

Sorry to hear that. Pull off the l.u. if you haven't done that, to make absolutely sure it's the powerhead. Do a postmortem, hopefully premature -- 24:1 fuel mix, pumping water -- no overheating(?). Remove the head cover and bypass covers and begin looking.

 

[tpls63]

Not the LU. Pumping water fine and the head was not hot when it quit. Do you know if parts are available to rebuild it? Is the 1956 evinrude 30HP the same block? Mine is a Johnson rde18c 1956 30Hp

 

[F_R]

Evinrude and Johnsons are the same, as long as same year. When you find what parts you need, post a want ad on the Antique Outboard Club's website www.aomci.org The ad is free.