Johnson 6RL72D - From Biohazard to Boat Motor in a Hundred Not So Easy Steps
Don't look directly at it.
I actually found this motor several months ago on Marketplace. I had recently rebuilt a 6R70B which was a 1970 model 6hp. I thoroughly enjoyed that build/flip and kept my eyes open for another. So when this one popped up, I acted quickly.
It was ugly. Really ugly. Like, "give-you-an-infection-just-by-looking-at-it" ugly. And it looked like it was in rough shape mechanically, and the seller advertised it as "not running".
Nevertheless, I'm stupid, so I gleefully dove in head first...messaged the seller...asked if he still had it and if the shifter was broken.
Yes, he still had it, he said. No comment on the shifter. And he wanted me to call him.
Now, I use Marketplace because it accommodates my loathing of talking on the phone. I can do all my transactions without having to talk to people. We have local trader's guides that operate solely off of phone usage. But, I avoid those so I won't have to use the phone. And this guy was trying to intermingle the two worlds, which was totally unacceptable. So, I gave up.
But, the motor kept coming up on my Marketplace feed. Eventually, I messaged him again, this time late at night. Again, he asked me to call.
I made an excuse. "I'm in bed on my phone. Wife's asleep next to me. Can't call you right now."
Sometimes my genius astounds even me.
So, he had to type stuff, and he probably felt the same way about typing as I do about talking on the phone. But, I had established dominance in this conversation and was taking it in the direction I wanted to go.
It was obvious from the pics that the gear shifter had been broken. But, despite my establishment of dominance, the seller didn't want to talk about that, or anything else.
I asked about it again, and again, he avoided the question. "I've never messed with it." he said. I did drag some details out of him, including an asking price: $125. I figured the carb alone was probably worth that. So, I set up a meeting. Made the trip, paid the money.
When I got it home, I began tearing it apart. The tiller handle was messed up and incorrectly assembled to the point that it would not turn the throttle control. Someone had tried to fix it and left it completely non-functional. Separated the halves, put new hardware on it, and got it working.
Next was to see if the lower was healthy. I pulled it and it looked good...impeller was intact, oil was clean, etc.
But when I started it, it ran poorly, and only on one cylinder. I pulled the flywheel, and found that someone had "worked" on the engine. The coils, points, and condenser all looked new and correctly installed, which was good. But, one of the spark plug wires wasn't even touching its coil. Someone had worked on it, and left it completely non-functional.
I asked about it again, and again, he avoided the question. "I've never messed with it." he said. I did drag some details out of him, including an asking price: $125. I figured the carb alone was probably worth that. So, I set up a meeting. Made the trip, paid the money.
When I got it home, I began tearing it apart. The tiller handle was messed up and incorrectly assembled to the point that it would not turn the throttle control. Someone had tried to fix it and left it completely non-functional. Separated the halves, put new hardware on it, and got it working.
Next was to see if the lower was healthy. I pulled it and it looked good...impeller was intact, oil was clean, etc.
But when I started it, it ran poorly, and only on one cylinder. I pulled the flywheel, and found that someone had "worked" on the engine. The coils, points, and condenser all looked new and correctly installed, which was good. But, one of the spark plug wires wasn't even touching its coil. Someone had worked on it, and left it completely non-functional.
I fixed that, then spent the rest of the day learning the hard way about suppression core wires and why they are garbage for old outboards...they're designed to limit interference to the radio and car electronics by reducing the intensity of the spark. Well, the old Johnson is a points and condenser system, so it doesn't produce a ton of spark to begin with, and the suppression core wire was killing what little fire I had.
Finally found some mag-core agricultural wires at the local parts store, installed them, and that solved the problem. I assume that this was a large part of why the motor was sold to begin with. It had a new cheapo aftermarket fuel pump on it, new plug wires, etc. Someone had made an attempt to get it running and had failed.
By the way, if you ever pull the lower on one of these, do NOT ignore the roll pin in the driveshaft. Without it, you have no lower crank seal, and best case scenario, you have a mess in the exhaust housing. At worst, you'll burn up your engine, because your engine will always run lean, as the gas/oil will leak out the bottom crank instead of making it into the cylinders. That little pin compresses that whole contraption above into place and makes the difference in whether your engine will ever run correctly. No need to get the OEM model...in fact, I bought an assortment of stainless metric roll pins and one of them works just fine. I don't know the diameter or length. I just try different ones until one fits. According to the AI's, it's 3/4" long by 3/16" in diameter, so find one close to that. Oh, and you have to have the pin facing side to side (perpendicular to the line of travel when going straight) when installing the lower/driveshaft or the pin will never go into place. Ask me how I know, lol.
Probably one of the most fun endeavors you will ever undertake is simultaneously threading the roll pin through the slot way up in the exhaust housing while lining up the water tube and making sure the shift shaft goes into place correctly, then holding the whole thing while you tighten down the shift coupler and start the first bolt through the lower and into the exhaust housing. Those OMC engineers knew that people like a challenge. So many hours of entertainment.
As a bonus, in the process of removing the power head, I cracked a bolt and had to remove the stub through some torque and "thermal persuasion". Eventually, I was able to replace it with another bolt that had the same thread size. I put all of the bolts, which were stubborn to the last one, back in with anti-seize.
But now, it was alive. Not the smoothest in the world, but it ran.
I noticed that it seemed to never get up to temperature, always running in the low 100s. I pulled the thermostat and found my answer...
So, obviously, some new parts would be needed.
Over the course of the next two weeks, I did all sorts of repairs and upgrades...fuel pump rebuild, new fuel lines, new fuel coupling, new spark plugs, Sierra carb kit, among other things. It was dumping a LOT of oil into the exhaust housing, so I knew I would have to pull the powerhead and replace the crank seal. The old one, made of cork and pressed against the bottom of the engine by a Rube Goldberg spring mechanism, had been mashed flat until it no longer sealed anything, so I made a new one out of some 1/8" thick Fel-Pro 3019 cork gasket material to replace it. This is some good stuff and I've since found a few other uses for it.
I noticed that it seemed to never get up to temperature, always running in the low 100s. I pulled the thermostat and found my answer...
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| They're not supposed to come with a salad. |
So, obviously, some new parts would be needed.
Over the course of the next two weeks, I did all sorts of repairs and upgrades...fuel pump rebuild, new fuel lines, new fuel coupling, new spark plugs, Sierra carb kit, among other things. It was dumping a LOT of oil into the exhaust housing, so I knew I would have to pull the powerhead and replace the crank seal. The old one, made of cork and pressed against the bottom of the engine by a Rube Goldberg spring mechanism, had been mashed flat until it no longer sealed anything, so I made a new one out of some 1/8" thick Fel-Pro 3019 cork gasket material to replace it. This is some good stuff and I've since found a few other uses for it.
 |
| Seems like a reasonable design. |
Probably one of the most fun endeavors you will ever undertake is simultaneously threading the roll pin through the slot way up in the exhaust housing while lining up the water tube and making sure the shift shaft goes into place correctly, then holding the whole thing while you tighten down the shift coupler and start the first bolt through the lower and into the exhaust housing. Those OMC engineers knew that people like a challenge. So many hours of entertainment.
As a bonus, in the process of removing the power head, I cracked a bolt and had to remove the stub through some torque and "thermal persuasion". Eventually, I was able to replace it with another bolt that had the same thread size. I put all of the bolts, which were stubborn to the last one, back in with anti-seize.
Removing the power head was also the only way to get to the shift coupling. It's no wonder the guy didn't want to talk about the shift lever. Not only was it broken, it was also disconnected. The piece that connected the shift handle to the shift rod was cracked and partly missing. I managed to find another one on eBay for around $10, and when I put it back together, it shifted just fine.
About that shift handle...I ended up having to re-make half of it out of PVC, which I molded using a heat gun. It ended up being quite sturdy and it looks and functions like it was made that way.
About that shift handle...I ended up having to re-make half of it out of PVC, which I molded using a heat gun. It ended up being quite sturdy and it looks and functions like it was made that way.
Redneck engineering.
Then, I installed a new water impeller housing and impeller. I'm still not sure I made the right decision on this. The old design has a much larger impeller, simpler housing, and no gaskets. It also pumps water in greater volume, if you ask me.
The new impeller kit is designed to use the updated OMC style impellers, which , IMHO, are not as robust. I did put the new housing and impeller on, and when I took it back apart to chase down the leak, I found that it had chewed up the gasket underneath. Had any of that come loose and gotten sucked up into the engine, I would be in a bad situation, likely dealing with an overheat. I made a new gasket and put it back together, but if the same problem occurs again when I go to swap out the driveshaft seal, the old impeller and housing will go back in temporarily and I'll just order a new impeller for the old housing.
After that, new oil in the gear case, which unlike before, now showed signs of contamination after running it in a barrel. Pressure testing revealed tiny bubbles around the drive shaft seal, and I have one on order, which hopefully solves the problem.
Finally, it was time to do water testing. This video shows the motor at every step of the restoration process except for the final cosmetic overhaul.
Speaking of that, it was time to do something about the way the thing looked. One previous owner had done a ham-fisted attempt at painting the cowl. It was bad...he didn't have replacement decals, so he just taped over the old logos and didn't paint that part. Are you seeing a pattern here? The cowl gasket was shot, as it was cracked, weathered, and in pieces. The "olive gold" paint on the lower was worn down to the red primer.
I tried on the previous Johnson 6 to restore a factory appearance using what was available on eBay and at WalMart, with mixed success. I was never happy with the way it ended up looking but really didn't want to put any time into correcting it, so I sold it as it was. It wasn't that it was bad, it just looked like someone had tried to make it look original and had failed. This is because I had tried to make it look original and failed.
This time, I decided to skip any claim to authenticity and instead tried to bring the Johnson into the 21st century with a modern paint scheme. I used a sand colored semi-gloss on the cowling (I think the name for that color is "Fossil"), and Rustoleum Appliance Paint in black on everything else but the prop, which also got the fossil treatment. I can't say enough about the Rustoleum Appliance Paint. It's an epoxy that goes on easy with an amazing gloss, and is tough as nails after it dries. It does take a little longer to harden, but it's worth the extra time. Afterward, I replaced the cowl gasket with one from AliExpress, and the Johnson decals came from AliExpress as well.
The new impeller kit is designed to use the updated OMC style impellers, which , IMHO, are not as robust. I did put the new housing and impeller on, and when I took it back apart to chase down the leak, I found that it had chewed up the gasket underneath. Had any of that come loose and gotten sucked up into the engine, I would be in a bad situation, likely dealing with an overheat. I made a new gasket and put it back together, but if the same problem occurs again when I go to swap out the driveshaft seal, the old impeller and housing will go back in temporarily and I'll just order a new impeller for the old housing.
After that, new oil in the gear case, which unlike before, now showed signs of contamination after running it in a barrel. Pressure testing revealed tiny bubbles around the drive shaft seal, and I have one on order, which hopefully solves the problem.
Finally, it was time to do water testing. This video shows the motor at every step of the restoration process except for the final cosmetic overhaul.
Speaking of that, it was time to do something about the way the thing looked. One previous owner had done a ham-fisted attempt at painting the cowl. It was bad...he didn't have replacement decals, so he just taped over the old logos and didn't paint that part. Are you seeing a pattern here? The cowl gasket was shot, as it was cracked, weathered, and in pieces. The "olive gold" paint on the lower was worn down to the red primer.
 |
| Man, was it ugly. |
I tried on the previous Johnson 6 to restore a factory appearance using what was available on eBay and at WalMart, with mixed success. I was never happy with the way it ended up looking but really didn't want to put any time into correcting it, so I sold it as it was. It wasn't that it was bad, it just looked like someone had tried to make it look original and had failed. This is because I had tried to make it look original and failed.
This time, I decided to skip any claim to authenticity and instead tried to bring the Johnson into the 21st century with a modern paint scheme. I used a sand colored semi-gloss on the cowling (I think the name for that color is "Fossil"), and Rustoleum Appliance Paint in black on everything else but the prop, which also got the fossil treatment. I can't say enough about the Rustoleum Appliance Paint. It's an epoxy that goes on easy with an amazing gloss, and is tough as nails after it dries. It does take a little longer to harden, but it's worth the extra time. Afterward, I replaced the cowl gasket with one from AliExpress, and the Johnson decals came from AliExpress as well.
Finally, she was (mostly) done. Not only does the engine start and run easily, it pulls very well and can push a 1542 jon at 8 mph with two big guys and a dog in it. And it looks fantastic.
Can't ask for more than that from a 54 year old motor.
Here's the list of everything I've done to it...
- Sierra carb kit
- Thermostat
- Paint, hood gasket, decals
- Tiller handle ring (PVC)
- Fuel pump rebuild
- Fuel lines
- Fuel fitting
- Powerhead gasket
- Shift lever repair
- Shift linkage replacement
- Crank seal replacement
- Impeller and housing
- Lower unit oil
- Spark plugs and wires
- Cleaned points
- Pull rope for starter
- Decals for shift, choke, throttle, mixture, etc
Watch the Wrench and Rod store. This one may be for sale at some point.
As always, as an Amazon affiliate, I earn from qualifying purchases. All products that I have linked are products that I have purchased directly, or that I am familiar with through other means, unless noted otherwise. I will never suggest you purchase products of poor or unknown quality.
As always, as an Amazon affiliate, I earn from qualifying purchases. All products that I have linked are products that I have purchased directly, or that I am familiar with through other means, unless noted otherwise. I will never suggest you purchase products of poor or unknown quality.
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