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15 HP Johnson Outboard #5423003 05/06/20 08:08 PM
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mobilaltima Offline OP
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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?

Last edited by wwillson; 05/07/20 06:35 AM. Reason: subject clarification

2006 2500 Dodge 5.9 Cummins Mobil Delvac 15W40, Fleetguard Stratapore 90k miles
Early '99 F250 ECLB 7.3 Stroker, 223k miles
Re: 15 HP Johnson Outboard [Re: mobilaltima] #5423022 05/06/20 08:29 PM
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JohnnyJohnson Offline
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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.


2004 Corolla 140120
Out: Havoline Pro DS 10w-30 Purolator PureOne 10-29-19 136457
In: Pennzoil Platinum HM 5W-20 ST 4386
2006 Duramax 77077
Out: T6 5W-40 XG9100 73909
In: Rotella Dino PH9100 11-3-19
Re: 15 HP Johnson Outboard [Re: mobilaltima] #5423024 05/06/20 08:31 PM
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Bluestream Offline
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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

Last edited by Bluestream; 05/06/20 08:35 PM.

2000 VW Beetle 1.8T M5
2006 Pathfinder 4X4
1991 BMW 735iL
"A fool and his money are soon parted" - Thomas Tusser
Re: 15 HP Johnson Outboard [Re: mobilaltima] #5423102 05/06/20 10:26 PM
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whosmatt Offline
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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.

Re: 15 HP Johnson Outboard [Re: mobilaltima] #5423439 05/07/20 01:58 PM
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Tman220 Offline
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https://www.leeroysramblings.com/Outboard%20Motor%20Related/OMC%20outboard%20related%20articles.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


2012 Regal GS Turbo PP 5w30 90k
1994 Camaro Z28 LT1 355 CI, 430 RWHP PP 5W30 165k
2005 GMC Sierra 1500 5.3 170k
2004 Civic LX M5 190k
2007 Camry 2.4 250k
2016 Victory Vegas
Re: 15 HP Johnson Outboard [Re: mobilaltima] #5423525 05/07/20 04:30 PM
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joekingcorvette Offline
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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.


2005 Chevrolet Corvette
2014 Ford F-150 4x4 supercrew
2014 Jeep Grand Cherokee Limited (wifes)
2012 Honda Civic 4 door (my daily driver)
2007 Lund Tyee Grand Sport Mercury 115HP 9.8HP
Re: 15 HP Johnson Outboard [Re: mobilaltima] #5423634 05/07/20 08:02 PM
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Warlord Offline
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The Rudeson 9.9/15 are some of the best outboards ever made. Excellent power to weight and reliable as a hammer.


81 Ford 1100 - daily driver
07 GMC Canyon - 245000 km
08 Honda CRF230L - 5000 km
Re: 15 HP Johnson Outboard [Re: Warlord] #5423641 05/07/20 08:12 PM
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Bluestream Offline
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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/

Last edited by Bluestream; 05/07/20 08:14 PM.

2000 VW Beetle 1.8T M5
2006 Pathfinder 4X4
1991 BMW 735iL
"A fool and his money are soon parted" - Thomas Tusser
Re: 15 HP Johnson Outboard [Re: Bluestream] #5423867 05/08/20 07:28 AM
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Tman220 Offline
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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.


2012 Regal GS Turbo PP 5w30 90k
1994 Camaro Z28 LT1 355 CI, 430 RWHP PP 5W30 165k
2005 GMC Sierra 1500 5.3 170k
2004 Civic LX M5 190k
2007 Camry 2.4 250k
2016 Victory Vegas
Re: 15 HP Johnson Outboard [Re: Tman220] #5424664 05/09/20 10:56 AM
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Bluestream Offline
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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.


2000 VW Beetle 1.8T M5
2006 Pathfinder 4X4
1991 BMW 735iL
"A fool and his money are soon parted" - Thomas Tusser
Re: 15 HP Johnson Outboard [Re: Bluestream] #5424692 05/09/20 11:50 AM
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Tman220 Offline
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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.


2012 Regal GS Turbo PP 5w30 90k
1994 Camaro Z28 LT1 355 CI, 430 RWHP PP 5W30 165k
2005 GMC Sierra 1500 5.3 170k
2004 Civic LX M5 190k
2007 Camry 2.4 250k
2016 Victory Vegas
Re: 15 HP Johnson Outboard [Re: mobilaltima] #5426027 05/11/20 06:07 AM
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Warlord Offline
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I stand by my earlier comment. They’re a darn fine outboard.


81 Ford 1100 - daily driver
07 GMC Canyon - 245000 km
08 Honda CRF230L - 5000 km
Re: 15 HP Johnson Outboard [Re: mobilaltima] #5426825 05/11/20 09:05 PM
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mobilaltima Offline OP
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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?


2006 2500 Dodge 5.9 Cummins Mobil Delvac 15W40, Fleetguard Stratapore 90k miles
Early '99 F250 ECLB 7.3 Stroker, 223k miles
Re: 15 HP Johnson Outboard [Re: mobilaltima] #5427918 05/13/20 07:16 AM
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Tman220 Offline
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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?


2012 Regal GS Turbo PP 5w30 90k
1994 Camaro Z28 LT1 355 CI, 430 RWHP PP 5W30 165k
2005 GMC Sierra 1500 5.3 170k
2004 Civic LX M5 190k
2007 Camry 2.4 250k
2016 Victory Vegas
Re: 15 HP Johnson Outboard [Re: mobilaltima] #5427928 05/13/20 07:24 AM
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Tman220 Offline
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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]


2012 Regal GS Turbo PP 5w30 90k
1994 Camaro Z28 LT1 355 CI, 430 RWHP PP 5W30 165k
2005 GMC Sierra 1500 5.3 170k
2004 Civic LX M5 190k
2007 Camry 2.4 250k
2016 Victory Vegas
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