# Johnson 15HP Outboard



## TMonter (Jun 10, 2013)

I have sort of an odd problem on my used 15HP (J15RCIS) Johnson outboard for my boat and wondering if anyone else has run into this.

Most of the time the motor runs beautifully and starts and runs very well. Twice this year though when I've been out on the lake it runs fine most of the day but then you'll start it, head off get the boat onto plane and the motor will just dies like it's not getting gas. At that point I can pull start it and it's won't catch unless I choke the motor and even then it won't stay running.

Both times it's happened when I took the cover off the top of the motor it's finally started and run okay even when I put the cover back on.

The plugs look good and are a light tan and were just replaced (It's done the same thing on two different sets of plugs).

I'm leaning towards either something in the carb bowl or a float sticking closed, or some type of electrical issue, possibly a bad powerpack.

Anyone familiar with this series of motor have any ideas? I might just bite the bullet and do a carb rebuild and go from there.


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## Jags (Jun 11, 2013)

T - water in your fuel will do that.  You can either pull the carb down and clean the ENTIRE fuel system, or if you want to try it, run a heavy mix of seafoam in it.  Sometimes that is all it takes, but often it will take several tanks of fuel/seafoam to really get the job done.

Obviously this is not the ONLY thing that can cause your issue, but fairly common.


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## TMonter (Jun 11, 2013)

Jags said:


> T - water in your fuel will do that. You can either pull the carb down and clean the ENTIRE fuel system, or if you want to try it, run a heavy mix of seafoam in it. Sometimes that is all it takes, but often it will take several tanks of fuel/seafoam to really get the job done.
> 
> Obviously this is not the ONLY thing that can cause your issue, but fairly common.


 
Thanks Jags, that is a good thought as some of the gas is from last fall but it was Ethanol free and stabilized with marine stabil. I'll try completely fresh gas in one of my gas tanks for the motor and give it a shot.


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## Jags (Jun 11, 2013)

The seafoam will help also.  It will actually absorb water and allow it to get burned up.


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## TMonter (Jun 11, 2013)

Jags said:


> The seafoam will help also. It will actually absorb water and allow it to get burned up.


 
I'll have to stop by Napa and pick up a fresh bottle of SeaFoam and do that as well.


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## semipro (Jun 11, 2013)

Sounds like you might have a fuel supply problem to me. If choking will get it to fire off then die then I doubt it has an ignition/electrical problem.
I'd suggest:

Making sure the tank vent is actually venting; not clogged or malfunctioning. When the problem occurs unscrew the fill cap on a portable tank an listen for a rush of air flowing in. The tank may also collapse a bit as vacuum builds inside. Not sure you're using a portable tank though.
Check the fuel filter in the tank and at the engine. The fuel pump may have a screen on the inlet that can get clogged.
Vapor lock can also be a problem on outboards. You might look into how to diagnose/prevent that.
If you have water in the fuel system it will settle in the low spots (tank, carb bowl, fuel pump housing). It can take quite a bit of time to work it though the system using fuel drier (i.e.,,alcohol) alone. It helps to remove what you can mechanically first.

BTW:
Seafoam is a mixture of naptha (very similar to kerosene) light fuel oil, and isopropyl alcohol.
http://www.mta.ca/administration/facilities/safety/msds/Grounds/Seafoam Auto Marine Engine treatment - SeaFoam Sales Co. 2010.pdf

If interested in making it yourself instead of paying what seems like an outrageous price for such cheap ingredients:
http://hildstrom.com/projects/seafoam/


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## WeldrDave (Jun 11, 2013)

I'm not a outboard mechanic by any means, "BUT" everybody that has mentioned seafoam is on the track!  what I've seen with the mechanics in the USN and the CG is 1 cup of K1 kerosene, and 1 shot glass of acetone in 3 gals of gas.  Run it through the engine till it's done then start with your normal mixture, usually 50 : to 1  this should kill the bug's!


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## TMonter (Jun 11, 2013)

Well it turns out it was indeed an electrical problem which was sort of unexpected but given the nature of the intermittent problem understandable. The previous owner of the motor has done some work and neglected to put some spacers under the coil packs and the plastic casings had melted and they were arcing and intermittently shorting out. I'll be ordering new coils for it in the morning. I'll still likely buy a can a seafoam to treat my gas but it's nice to find out what my issue was. I'll try and post some pictures of the issue later.


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## Jags (Jun 12, 2013)

Good diagnosis.  Some electrical problems are a biotch to get figured out.


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## TMonter (Jun 12, 2013)

Jags said:


> Good diagnosis. Some electrical problems are a biotch to get figured out.


 
What led me to it was when I was running the motor in the driveway with the hose on it and the cover off I could hear some popping by the coils occasionally.







You can see the coil on the left has been melted from not using a heat-resistant spacer to prevent it and the coil on the right has started as well. I ordered two new coils at about ~$27 each






You can see where the heat has damaged the casing and stray sparks were actually popping out of this crack occasionally.






This coil didn't have the extended heat damage.

Still considering I got the motor for $350 because it had a improperly adjusted recoil starter assembly which was fixed for free I'm doing pretty well.


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## Jags (Jun 12, 2013)

Yeah - that coil on the left is looking pretty toasty.  Is the spacer for air circulation?

$350 for a good 15hp is a pretty decent deal.


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## TMonter (Jun 12, 2013)

Jags said:


> Yeah - that coil on the left is looking pretty toasty. Is the spacer for air circulation?
> 
> $350 for a good 15hp is a pretty decent deal.


 
The spacer is so that heat from the engine block which the coil packs mount to doesn't damage the coils like this I suspect. I'm also going to install some small insulating pads made of heat resistant fiber between the coils and the engine mount and the spacers. I'll take another couple pictures when I get the new coils and get things reassembled.

So far I'm liking the Johnson/Evinrude design on this motor, it's simple and easy to work on.


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## Todd 2 (Jun 13, 2013)

Hows your water pump impeller (cooling system) if that coil was on top thats where the head gets the hottest.
Ive seen coils melted even with the spacers when there running hot, just a thought if it hasn't had a new impeller in a while.

Todd


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## TMonter (Jun 14, 2013)

Supposedly the impeller was changed last year but after I get the new coils on it tomorrow, I plan on running it with the muffs on it and see how hot the engine gets. The impellers are cheap ($15) so I should be able to get one no problem. I do get water out of the overflow hole when it's running so I know water is getting in the motor okay. I should likely check the thermostat as well when I look at things tomorrow.


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## Dune (Jun 16, 2013)

We just put in a new water pump every spring as rule of thumb.


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## semipro (Jun 16, 2013)

Dune said:


> We just put in a new water pump every spring as rule of thumb.


 
I'm curious.  Do you also replace the sacrificial anode often when operating in a salt water environment?


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## Dune (Jun 16, 2013)

semipro said:


> I'm curious. Do you also replace the sacrificial anode often when operating in a salt water environment?


Of course. On many motors it needs to be removed to replace the water pump anyway.


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## semipro (Jun 16, 2013)

Dune said:


> Of course. On many motors it needs to be removed to replace the water pump anyway.


 
I've only operated outboards in fresh water so I've never had one corrode away.  Was just wondering how often they're replaced for salt water use.


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## TMonter (Jun 16, 2013)

TMonter said:


> Supposedly the impeller was changed last year but after I get the new coils on it tomorrow, I plan on running it with the muffs on it and see how hot the engine gets. The impellers are cheap ($15) so I should be able to get one no problem. I do get water out of the overflow hole when it's running so I know water is getting in the motor okay. I should likely check the thermostat as well when I look at things tomorrow.


 
I didn't have to change the impeller as the motor is pumping water very well. The new coils are installed and working very well. Some of the rough starting and the problems with the motor running smooth at trolling speeds is now fixed but I still have a fuel issue with the motor. Yesterday at the lake it worked great for about the 20 minute run to the fishing spot and then when I restarted the motor it ran fine for about 20 seconds until it conked out like it wasn't getting fuel. I was able to restart it by pumping the primer bulb until the carb was full so I'm pretty certain I'm getting some sort of vaporlock. I may have either have a sticky float needle, or possibly a fuel pump that is starting to fail. I also noticed the connection on my hose to the motor may need a new o-ring.

So a few more things to do to this motor but at least it's easy to work on. It runs like a champ, other than the hot restart issue and that can currently be worked around while I slowly get things fixed. I'll likely order a new fuel pump, spare impeller and fuel connection later this week on Amazon.

By the time I'm all said and done my move from a 9.5HP to a 15HP is going to cost me about $200


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## Ehouse (Jun 16, 2013)

Check fuel line and connectors.  Even though they look identical, OMC and Merc etc. are not the same.  If you switched motors but not lines you may have a misfit.  Even a small amt. of fuel leakage at a connector indicates air getting in ,and can stop you cold.


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## TMonter (Jun 16, 2013)

Ehouse said:


> Check fuel line and connectors. Even though they look identical, OMC and Merc etc. are not the same. If you switched motors but not lines you may have a misfit. Even a small amt. of fuel leakage at a connector indicates air getting in ,and can stop you cold.


 
Old motor was a Johnson as well but I did replace the fuel line connector today and I know the ones on the tank are good. Now it's basically down to the fuel pump and the carburetor. If I do anything with the carburetor it's going to be a complete service and cleanup.


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## Jags (Jun 17, 2013)

Yep - even small fuel "sealing" issues can have weird effects on a boat motor.  The smaller the motor, the more drastic the effects.  Make sure all connections have a proper fit and seal.  I have a 6 gallon tank that needs a new o-ring.  The engine runs fine if you are above idle or get'in it, but if you try to idle on that tank - no go.  No problems with the 12 gallon tank, so I know it is a tank issue.


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## TMonter (Jun 17, 2013)

Here is a few more pictures of the new coils installed.










You can see the new coil pack and I put fiber spacers under both packs where they used to touch the engine block. The block should never get hot enough to damage them but this should give me some extra insurance.

I think this winter this may become a cleanup project for me. I'm sort of a fanatic about keeping my equipment in a "like new" condition and this motor while decently maintained was not kept very clean. Mechanically it's sound but it's a bit dirty for my tastes.


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## TMonter (Jun 17, 2013)

Jags said:


> Yep - even small fuel "sealing" issues can have weird effects on a boat motor. The smaller the motor, the more drastic the effects. Make sure all connections have a proper fit and seal. I have a 6 gallon tank that needs a new o-ring. The engine runs fine if you are above idle or get'in it, but if you try to idle on that tank - no go. No problems with the 12 gallon tank, so I know it is a tank issue.


 
Well what is strange Jags is that if I pump the carburetor full when it does this whole issue and then keep pumping the carb full for about 15 seconds after getting the motor to full throttle it stays running. This is why I suspect some type of fuel pump or float issue although I am leaning more to a fuel pump issue. I'm still not sure if the pump can be rebuilt on this one or if I need to just buy a whole new pump. I'm hesitant to take it apart until I have the new pump in hand since I want to get out fishing a couple evenings this week.


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## Jags (Jun 17, 2013)

Shoot - I would slap the lid back on it and run it for the next 20 years, but thats me.

My bad tank acts the same, but at an idle.  At an idle it can't pull enough vacuum to over come the air leak.  Priming the bulb does.  If you question the tank, start there. It is possible that the fuel pump could have issues, but a simple o-ring is an easy thing to eliminate.
And from experience I can tell you that even a small air leak in the fuel line can and will cause some weird behavior.


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## TMonter (Jun 17, 2013)

Jags said:


> Shoot - I would slap the lid back on it and run it for the next 20 years, but thats me.
> 
> My bad tank acts the same, but at an idle. At an idle it can't pull enough vacuum to over come the air leak. Priming the bulb does. If you question the tank, start there. It is possible that the fuel pump could have issues, but a simple o-ring is an easy thing to eliminate.
> And from experience I can tell you that even a small air leak in the fuel line can and will cause some weird behavior.


 
I have two tanks and it does the same thing on both tanks so it's definitely not a tank issue. The other indicator is that it only seems to do this when the motor is hot. I replaced the connector to the motor yesterday so we'll see how it goes later this week.


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## Jags (Jun 17, 2013)

I don't remember if that is a vacuum operated pump or mechanical.  If vacuum - make sure you don't have any other leaks to deal with.


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## TMonter (Jun 17, 2013)

Jags said:


> I don't remember if that is a vacuum operated pump or mechanical. If vacuum - make sure you don't have any other leaks to deal with.


 
It's a vacuum operated diaphragm pump operated off of crankcase vacuum. I sort of wish it were mechanical but this design looks simple enough. A whole new pump is about 40 bucks it looks like:

http://www.amazon.com/gp/product/B000N9LCH8/ref=ox_sc_act_title_4?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

Or I can rebuild it for about 1/3 the cost:

http://www.amazon.com/gp/product/B0009TOBTI/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

I'll likely go for the rebuild but as I understand it they are sort of a PITA to rebuild.


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## TMonter (Jul 8, 2013)

TMonter said:


> It's a vacuum operated diaphragm pump operated off of crankcase vacuum. I sort of wish it were mechanical but this design looks simple enough. A whole new pump is about 40 bucks it looks like:
> 
> http://www.amazon.com/gp/product/B000N9LCH8/ref=ox_sc_act_title_4?ie=UTF8&psc=1&smid=ATVPDKIKX0DER
> 
> ...


 
Well I finally solved the problem this last week and it turned out to be a old diaphragm in the pump that had gotten soft and wouldn't suck hard enough when it got air in the line. I bought a rebuild kit online for 12 bucks, got it running good and then promply sold it after I bought a mid-90's 4-stroke mercury on craigslist.

The bonus is I sold it for a couple hundred more than I bought it for. (Bought for $350, sold for $550)


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