15 HP Johnson Outboard

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Feb 3, 2011
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Golden Meadow, LA
Came out ahead on the 20 Mariner with low compression, sold it for $300 and picked up a 1976 15 Johnson from an old man who hadnt used it in 2 years for $200. Took it to one of my friends who is pretty good with outboards who said the carrier bearing behind the prop needs to changed, and I'll put a new impeller also. We sprayed some gas in the carb and it fired up with 3 pulls. So just how good are these small Johnson outboards from the 70's? I heard theyre near bulletproof. I plan on running non ethanol gas, for oil would Supertech be fine or should I use a different 2 stroke oil? 50:1 ratio or 40:1?
 
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50:1 I'd get the QuickSilver or Johnson's current synthetic. I just gave my 65 Evinrude to my Son-in-law and Grandson best trolling motor I ever owned.
 
They're ok. What year is it? 74-76 had the infamous OMC "low tension" Magneto. Not the best design, hopefully someone swapped it out for the CDI version
 
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They're pretty bulletproof, or in my case, idiot proof. I had one, I think it was an '81, that I picked up with a boat and trailer for $400. I had no idea what i was doing at the time. The motor wouldn't turn over so i just wrestled the flywheel until it did (no lube in the cylinders). Dumb, I know. It was missing a fuel pump and once I installed that and rebuilt the carb it ran like a top for years; I put many hundreds of hours on it with nary a problem. 50:1, any TCW-3. The supertech oil will be great; I ran that more than anything else.
 
https://www.leeroysramblings.com/Outboard Motor Related/OMC outboard related articles.html

Here is a great website for researching these engines.

I have a 1975 9.9 myself and it's a great engine. The ignition systems are really not so bad once you make some adjustments to spark plug use and oil fuel mix depending on your usage.

If you plan on running the sucker wide open all day stick with 50:1 mix. If you plan to do a bunch of trolling or using it as a kicker there is nothing wrong with dropping it down to 75:1
 
Yes those old Johnson's and Evinrudes are great engines. I have gone to the 4 strokes now but the those motors run forever. I never had any problems other than replacing a coil once on a 35 HP Evinrude/Johnson.
 
Originally Posted by Warlord
The Rudeson 9.9/15 are some of the best outboards ever made. Excellent power to weight and reliable as a hammer.


I've owned many over the years, and also an OMC guy, but the Mercury/Mariner 9.9/15 hp 1986+ 2-strokes are so far ahead of those OMCs its incredible. Having said that, if you've picked up and old outboard, and it meet your needs, go for it.

Here's your 1974-76 low tension magento gremlins

https://aomci.org/forums/topic/low-tension-magneto-question/
 
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Originally Posted by Bluestream
Originally Posted by Warlord
The Rudeson 9.9/15 are some of the best outboards ever made. Excellent power to weight and reliable as a hammer.


I've owned many over the years, and also an OMC guy, but the Mercury/Mariner 9.9/15 hp 1986+ 2-strokes are so far ahead of those OMCs its incredible. Having said that, if you've picked up and old outboard, and it meet your needs, go for it.

Here's your 1974-76 low tension magento gremlins

https://aomci.org/forums/topic/low-tension-magneto-question/

I doubt the OP gives a crap about those mercury's because he already stated he acquired the 15 hp OMC. The site you linked is mostly about someone piecing together an outboard from 10 other parts engines with unknown quality and unknown mechanical ability. Hardly transferable, other than showing the possibility of having bad 45 year old original parts. In the case with my 1975 9.9 I had weak spark on one of the cylinders, it turns out one of the two external ignition coils cracked and was allowing voltage to ground directly to the head. 40 bucks later and the thing has been completely flawless.

If someone wants to restore an outboard from this era it's hard to go wrong with this particular OMC. OMC owned the market back then, made quality stuff, parts are still available and cheap in comparison to a lot of stuff from mercury back in that time frame. The site I originally linked is a no bullcrap here are the quirks, here's how you fix them, here is what works. If you haven't had a chance to check it out you should.
 
Originally Posted by Tman220
Originally Posted by Bluestream
Originally Posted by Warlord
The Rudeson 9.9/15 are some of the best outboards ever made. Excellent power to weight and reliable as a hammer.


I've owned many over the years, and also an OMC guy, but the Mercury/Mariner 9.9/15 hp 1986+ 2-strokes are so far ahead of those OMCs its incredible. Having said that, if you've picked up and old outboard, and it meet your needs, go for it.

Here's your 1974-76 low tension magento gremlins

https://aomci.org/forums/topic/low-tension-magneto-question/

I doubt the OP gives a crap about those mercury's because he already stated he acquired the 15 hp OMC. The site you linked is mostly about someone piecing together an outboard from 10 other parts engines with unknown quality and unknown mechanical ability. Hardly transferable, other than showing the possibility of having bad 45 year old original parts. In the case with my 1975 9.9 I had weak spark on one of the cylinders, it turns out one of the two external ignition coils cracked and was allowing voltage to ground directly to the head. 40 bucks later and the thing has been completely flawless.

If someone wants to restore an outboard from this era it's hard to go wrong with this particular OMC. OMC owned the market back then, made quality stuff, parts are still available and cheap in comparison to a lot of stuff from mercury back in that time frame. The site I originally linked is a no bullcrap here are the quirks, here's how you fix them, here is what works. If you haven't had a chance to check it out you should.


I've spent a lot of time on Leroys ramblings. I even sent an email to him to thank him for the effort he put in, never received a replay, so assume he's passed, or busy. Never said OP outboards was junk, just said they were ok, which they are. As far as the link I posted, that fact that guy is piecing an outboard together from parts is irrelevant to the reliability and desirability of the OMC low tension magneto. It was a poor design and only lasted a few years. I can post 50 threads to support that, and speak from experience.
 
Originally Posted by Bluestream


I've spent a lot of time on Leroys ramblings. I even sent an email to him to thank him for the effort he put in, never received a replay, so assume he's passed, or busy. Never said OP outboards was junk, just said they were ok, which they are. As far as the link I posted, that fact that guy is piecing an outboard together from parts is irrelevant to the reliability and desirability of the OMC low tension magneto. It was a poor design and only lasted a few years. I can post 50 threads to support that, and speak from experience.


Actually it is relevant, you put junk into an equation you get junk out of it. I don't disagree that better ignition systems were used on that engine in later years, and the fact is, the early years are the least desired from an ignition stand point. My point is this, the OP acquired this outboard, he desires to fix it, I'm simply stating it's worth fixing and they do run well when you set them up correctly.

On these early 9.9/15 OMC's it's very important you take the time to set the points correctly, gap the coils under the flywheel properly, stabilize the the timing advance mechanism. check your external coils because it is common for them to crack. Replace the thermostat, it's likely original because they aren't easy to replace on the early models, but it's worth it because they will idle 10 times better when they are warm and not freezing cold due to a stuck open thermostat. Get rid of the surface gap spark plugs and go with something with ground straps and a .030" gap. I've done this on many of outboards from this era, and if you do so, you will be rewarded with an outboard that will idle all day without having to worry about fouling plugs, will start easy, and will troll down to very slow speeds.

It's a 45 year old outboard, if you think you can slap anything like that on your boat and expect it to be flawless you're barking up the wrong tree.
 
Took apart the foot today, I need to replace the bearing right behind the prop. The bearing is obsolete. Part Number 0386213, does anyone know where maybe I can find a NOS bearing?
 
Originally Posted by mobilaltima
Took apart the foot today, I need to replace the bearing right behind the prop. The bearing is obsolete. Part Number 0386213, does anyone know where maybe I can find a NOS bearing?

[Linked Image]

I assume it's #4 you need?
 
If #4 is what you need, it appears maybe a little dyslexia was involved because here is the number, very close to what you posted
[Linked Image]
 
Originally Posted by Tman220
Originally Posted by Bluestream


I've spent a lot of time on Leroys ramblings. I even sent an email to him to thank him for the effort he put in, never received a replay, so assume he's passed, or busy. Never said OP outboards was junk, just said they were ok, which they are. As far as the link I posted, that fact that guy is piecing an outboard together from parts is irrelevant to the reliability and desirability of the OMC low tension magneto. It was a poor design and only lasted a few years. I can post 50 threads to support that, and speak from experience.


Actually it is relevant, you put junk into an equation you get junk out of it. I don't disagree that better ignition systems were used on that engine in later years, and the fact is, the early years are the least desired from an ignition stand point. My point is this, the OP acquired this outboard, he desires to fix it, I'm simply stating it's worth fixing and they do run well when you set them up correctly.

On these early 9.9/15 OMC's it's very important you take the time to set the points correctly, gap the coils under the flywheel properly, stabilize the the timing advance mechanism. check your external coils because it is common for them to crack. Replace the thermostat, it's likely original because they aren't easy to replace on the early models, but it's worth it because they will idle 10 times better when they are warm and not freezing cold due to a stuck open thermostat. Get rid of the surface gap spark plugs and go with something with ground straps and a .030" gap. I've done this on many of outboards from this era, and if you do so, you will be rewarded with an outboard that will idle all day without having to worry about fouling plugs, will start easy, and will troll down to very slow speeds.

It's a 45 year old outboard, if you think you can slap anything like that on your boat and expect it to be flawless you're barking up the wrong tree.



It is relevant what the poster in my thread is doing with his franken-board. The point was to show the weakness of the low tension magneto, that has nothing to do with his project The other posters clearly demonstrated that weakness. I've owned these OMC 9.9's and they're an ok outboard. Nothing wrong with playing around with one as a project. Given my choice, I would take the 1986+ mercury 9.9/15. Even if they were a few hundred more.
 
Originally Posted by Bluestream

It is relevant what the poster in my thread is doing with his franken-board. The point was to show the weakness of the low tension magneto, that has nothing to do with his project The other posters clearly demonstrated that weakness. I've owned these OMC 9.9's and they're an ok outboard. Nothing wrong with playing around with one as a project. Given my choice, I would take the 1986+ mercury 9.9/15. Even if they were a few hundred more.

Again, that BS isn't relevant. MobilAltima, who owns this 15 HP OMC is getting help from others in this thread finding parts for it. He doesn't give a crap that some guy on some other thread has johnny cash's frankenrude and cant get the sparks to fly when MobilAltima is trying to fix his lower unit.
 
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