1957 Johnson 35 horse problems

[tgissel]

I have a 1957 RDE-19 Johnson 35 hp. Was running excellent last week. I changed plugs (same type, gap etc.) Motor now backfires and will not start but every once out of every ten tries. I tried the old plugs same effect. Good spark and gets fuel to carb. W/ the cover off of the motor there is a puff of smoke coming from behind the carb where the reeds are. Is this a bad pressure plug that the smoke is coming from? Or do I have other problems? Thanks

 

[Paul Moir]

Re: 1957 Johnson 35 horse problems

Put the plug wires on the other way.<br /><br />When I get a backfire now on I2's, it's like a light bulb going off. <br />(Pull, Pull, Pull, Yank, (swear), Yank, YANK, BANG, Dooohhh! (switch wires), Pull, Starts. )

 

[tgissel]

Re: 1957 Johnson 35 horse problems

Paul this motor still has the little brass tag on the plug wire that says "up". They are on the same way I have always run it. Thanks

 

[Paul Moir]

Re: 1957 Johnson 35 horse problems

Well so much for easy answers.<br /><br />The smoke, is it coming out of the carb throat or is it outside of the carb? If it's starting lean, it'll pop back through the carb (blowing past the reeds which naturally don't make a perfect seal).

 

[tgissel]

Re: 1957 Johnson 35 horse problems

Outside the carb, on the reed plate cover it looks like a tube is built into this at the very end is this supposed to be a bolt or a plug? Because the smoke looks to be coming from this area. It was running perfect last weekend.

 

[Paul Moir]

Re: 1957 Johnson 35 horse problems

Oh, you mean the hose nipple on the 'intake manifold', between the carb and the reeds? That should hook up to the vaccum cutout switch. If yours is missing it should be plugged for now until you get a new one. If it's open, you'll run excessively lean and have the exact problems your talking about.<br /> Cutout switch pic.

 

[tgissel]

Re: 1957 Johnson 35 horse problems

Paul, Okay I see the two hose nipples that are on the 'intake manifold' the one right behind the carb goes to the safety switch and the one below the carb goes back to the fuel tank conn. This is to the right of the bottom hose nipple and looks like a little brass knock-in plug. I think this is where the 'puff' of smoke is coming from.

 

[tgissel]

Re: 1957 Johnson 35 horse problems

The red paint job is nice though

 

[Paul Moir]

Re: 1957 Johnson 35 horse problems

I've got to post the rest sometime. <br /><br />Ok, I think I'm on the same page now - it is a plug to cover a drilled recirculation passage. If it's like the one I'm looking at, it's in on a 'tube' cast into the part.<br />If that's the case, then the passage it plugs is directly vented into the top crankcase chamber. It should be sealed, but I don't think that's what's causing your problem. It sounds to me like the engine has a lean sneeze, and it's blowing out through that plug. If that's the case, then spraying premix down the carb's throat from a windes bottle will make it run a bit or better.<br />It's possible that a bit of disintegrated hose or something is plugging up the carb. You won't know until you have it apart though.

 

[tgissel]

Re: 1957 Johnson 35 horse problems

Okay thanks Paul, I have not adjusted the carb (recently) and it was just rebuilt about two months ago, I will tear the carb apart and see what is in there. You are on the right page, that is the part I am talking about, but smoke should not come from this when the engine backfires should it? And the area around the plug has some paint missing like gas has eaten a little of it off. Thanks alot

 

[Paul Moir]

Re: 1957 Johnson 35 horse problems

No, it should be sealed well. If anything you'll run a bit better when it's tight. To fix it up, I would degrease it really well, and probably push some epoxy or 'Seal All' or some other gas resistant goo into it. I can't think of a really good way to fix it.<br />Double check that it's a fuel delivery problem before tearing apart the carb, and make sure fuel is actually getting up to the carb.<br /><br />Oh, by the way, I called that a recirculation passage, it's actually a fuel drain passage for puddled fuel. It ends up going into the drain valve in the bottom right of the block, and then dumped overboard next to where the driveshaft enters the crank. <br /><br />Good luck!

 

[tgissel]

Re: 1957 Johnson 35 horse problems

Thanks alot Paul, I was already planning to try to seal that up in some way. I am trying to determine the fuel problem currently. Thanks

 

[tgissel]

Re: 1957 Johnson 35 horse problems

Paul wouldn't a pressure gas tank have this same result 'lean-sneeze'?

 

[G DANE]

Re: 1957 Johnson 35 horse problems

If your motor ran well recently, I would pull the flywheel and check if it sheared the key, making spark way out of time.

 

[Paul Moir]

Re: 1957 Johnson 35 horse problems

It's fed through a check valve, so it can spurt out fuel/air, but it can't draw in fresh air which would modify the fuel/air ratio. Plus I think they have an oriface on it to prevent it from allowing too much fuel/air to escape each pulse. As a side note, I've seen outboards where the bottom crank seal has failed, and the bottom bearing got trashed from exhast particulates and water that got sucked in.<br /><br />Just to be clear, *don't* think that plug leak is causing the lean condition (if it even exists). It just can't have a great effect. Plus I think the engine would start or at least try to start on one cylinder.<br /><br />GDANE - since the timing on this engine is ultimately derrived from the cam on the crankshaft, a sheared flywheel key will only result in a weakened or lost spark, not bad timing.

 

[tgissel]

Re: 1957 Johnson 35 horse problems

Thanks GDANE, I think I discovered the problem the gas tank would not hold any pressure. I took the top off of the tank and the old cork seal was barely there, I don't know how it was ever holding pressure like this. If this does not fix it I will check the flywheel key. Thanks again,