1962 Johnson RDS-24M no fire upper cylinder

[reavesga]

I just purchased a 1962 Johnson 40HP RDS-24M for use on a 1961 boat. The goal is a restored classic. So, before I start taking the motor apart I thought I would check a couple of things. See if we have fire on both cylinders. So I disconnected the wire harness from the junction box so that the motor just has wires hanging out the front of it and removed the plugs. I hooked up a ground so that I could easily see the plug and check for spark. The motor pulls through nice and easy with the plugs out. Lower plug bright blue spark. Upper plug nothing. So I start looking at wiring diagrams and there are vaccum cutout switches, and interrupt switches, etc and they all appear to ground one of the magneto lines. So, the question is with a dead cold motor is spark on the lower plug only normal, or is there a wire I need to hook up some where to get spark on the upper plug. Or disconnect to check for a bad cutout switch and or vacuum switch or do I have a dead coil. Manuals are on the way. So far info on the web not conclusive as I just want to see if I have spark. And what is the purpose of the vacuum and cutout switches anyway. All my experience to date is with Mercruiser sterndrives so this is a new adventure.

The good news, the motor has compression on both cylinders 140psi or so best I can tell. Looks clean.

 

[reavesga]

Re: 1962 Johnson RDS-24M no fire upper cylinder

Think I followed the wires and disconnected the vacuum switch after confirming it was connected to ground. Still no spark on the upper. Starting to think upper coil or points is bad.

 

[lindy46]

Re: 1962 Johnson RDS-24M no fire upper cylinder

The vacuum cut-out switch cuts spark to the lower cylinder during a runaway situation. It does nothing to the upper cylinder. You will have to pull the flywheel to see what's going on. Most likely worn/dirty/misadjusted points or bad coil.

 

[kfa4303]

Re: 1962 Johnson RDS-24M no fire upper cylinder

Here are some handy links to get the old beast running again. You can get coils and/or a tune up kit right here at iboats for about $25 each.

http://www.duckworksmagazine.com/04/s/columns/max/24/index.cfm

http://www.outboard-boat-motor-repa...on 3 HP 1952-1967 Ignition System Tune-up.htm

 

[reavesga]

Re: 1962 Johnson RDS-24M no fire upper cylinder

Thanks....Great info. After reading that info I am betting on a cracked coil. WIll update once the flywheel is off.

 

[reavesga]

Re: 1962 Johnson RDS-24M no fire upper cylinder

Got the fly wheel off. Everything has been previously replaced. The coils look great. I pulled out the ohm meter and started checking things. What I found is that the coil that fires measures a dead short across the condensor, lead to case. The coil that does not fire reads 2kohms. Everything else is identical between the two ignition systems. I pulled the points on the none firing coil and they were some what pitted. So my guess is bad condensor, lead to failed points. Also high tension leads look some what worn as well as the grounding leads. Was thinking of replacing everything including the coils on both systems that way I know everything is new.

 

[reavesga]

Re: 1962 Johnson RDS-24M no fire upper cylinder

Firing one is open not short. None firing is high resistance, but still circuit to ground. So that mag is grounded thus no fire.

 

[tx1961whaler]

Re: 1962 Johnson RDS-24M no fire upper cylinder

Points and condenser kit here: http://www.iboats.com/mall/partfind...gd_poid=111574&gd_row=26&session_id=547307675
Coils: http://www.iboats.com/mall/partfind...d_poid=109172&gd_row=149&session_id=547307675

 

[Willyclay]

Re: 1962 Johnson RDS-24M no fire upper cylinder

The good news, the motor has compression on both cylinders 140psi or so best I can tell.

Wow! Keep the battery charged up so you don't have to pull that beauty over by hand since it does not have the compression release feature. Nice find. Good luck with the project.

 

[reavesga]

Re: 1962 Johnson RDS-24M no fire upper cylinder

So I figured that the coil was good and the points and condenser were bad. So I replaced the points and condenser. Put it back together and, still no spark on the upper cylinder with the p-leads just hanging so I know they are not grounded. Lower is still sparking just fine. So, I am using an ohm meter to try to ring everything out. I am really confused everything seems to ring to ground on both the firing and non-firing. Then I notice that the coils have a little metal piece sticking through the center. I figure this must be the wiring connection inside the coil for the high tension side. On the firing coil it rings to ground. On the non-firing coil it does not ring at all. Not to ground, not to any lead coming out of the coil. Not even to the metal frame of the coil. So, is the coil bad? I really do not want to take apart the firing side to put the known good coil on the system. I have ordered a coil. Hopefully that is it.

 

[Daviet]

Re: 1962 Johnson RDS-24M no fire upper cylinder

If you have any doubts, swap the coils, if the spark follows the coil, you have a bad coil.

 

[oldman570]

Re: 1962 Johnson RDS-24M no fire upper cylinder

I had the same problem with a FD 22 A 20hp I have been working on. I was using the old plugs that were in the motor and were only 1 moth old. One of the plugs is bad and will not fire on the one plug wire but would on the other. Used a spark tester and only spark on #2 cyclender. Replaced the points and condensors and gap new points and new plugs and Bingo things work. I metered both coils and they were the same readings on both. If the coils read diffrent and ALL the coil wires are disconected from the points and ground, then one of the coils is bad on the winding in the coil. Using a spark tester for testing spark, is the only way I'll test for spark again.
Oldman570

 

[kfa4303]

Re: 1962 Johnson RDS-24M no fire upper cylinder

Here's a great magneto link.

http://www.outboard-boat-motor-repa...on 3 HP 1952-1967 Ignition System Tune-up.htm

 

[reavesga]

Re: 1962 Johnson RDS-24M no fire upper cylinder

All new parts on the way including plug wires. Will report back. My coil checks prr the articles procedure.

 

[reavesga]

Re: 1962 Johnson RDS-24M no fire upper cylinder

Points Points Points !!! Don't do no good if they are not set correct. The new points were gapped open correct but they were not actually closing. The voltmeter check described at http://www.outboard-boat-motor-repai... Tune-up.htm showed the problem. They sure looked closed to me, but they were not. Now I have spark.

Next question, how do you get the new spark plug wire through the new boot? I got it through the old boot, but the boot split. I have a new boot but can't seem to get it in there. Any suggestions? Is it ok to lub the wire with some grease or vaseline?

Also, can you put a hose on the lower unit somewhere to run the motor on the hose. Water ears will not fit due to the really small lower unit relative to modern units. I don't have a test tank.

 

[Daviet]

Re: 1962 Johnson RDS-24M no fire upper cylinder

Yes, you can lube the boot, I just use WD-40.
No, you need to put it in a trash can or barrel, make sure the water is almost up to the exhaust port.

 

[samo_ott]

Re: 1962 Johnson RDS-24M no fire upper cylinder

Buy a garbage can. You can not put muffs on that engine.

 

[kfa4303]

Re: 1962 Johnson RDS-24M no fire upper cylinder

+1. No mufs on these old motors as the waterpumps are NOT self-priming. Instead, you'll need a big trash can, or 55 gallon drum to use as a test tank. You'll then need to fill it with water to about and inch or two below the main exhaust port on the back of the motor. Here's a handy link with pics.

http://www.duckworksmagazine.com/04/s/columns/max/24/index.cfm

 

[reavesga]

Re: 1962 Johnson RDS-24M no fire upper cylinder

Trash can it is. Discovered that the motor will go horizontal on the stand so getting the can under it should not be a problem.

Now for the confession. I need a long shaft motor instead of the short shaft !!! I would have sworn the boat would work with both but it will not. So I go dig into the parts manuals and find out there is a kit. Any ideas on where to get the kit. Seems like there is a pluther of short shaft motors of this vintage but not that many long shafts.

 

[kfa4303]

Re: 1962 Johnson RDS-24M no fire upper cylinder

What makes you think you need a long shaft? The leg length on these old OMC motors is around 18", but most transoms are around 15". As a result, these old motors usually need to be raised a few inches, if anything. Unless you have a 20" transom you shouldn't really need the long shaft version. I have mine on a transom riser myself so that my antivent plate is level/lightly higher than my keel. However, it's not a big deal to convert it. All you need to do is get a longer drive shaft. water uptake tube, and lower shift rod. You simply swap out the old/short versions for the new/long versions and that's it. You can check ebay, aomci.org or some of the salvage years listed in the top secret file at the top of the forum for the parts.