# another Johnson 15 horse question



## doc1976 (Jan 16, 2017)

1985 johnson 15 horse. replacing water pump, got the sierra 18-3327 kit. 2 questions. first, the small o ring in the kit, where does it go? I have matched up all parts with the existing pump installed except for the small o ring. Maybe the kit fits multiple models and maybe others use the small ring? Second, what is the purpose of the water restrictor under the seal in the water pump housing? It shows that it is only used in the 15 horse model, not the 9.9. If you look at the schematic for the gearcase it is number 40.


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## Pappy (Jan 16, 2017)

The small O-ring is used as a driveshaft seal and is placed in the groove just under the splines at the top of the shaft on driveshafts with the o-ring groove. Regardless, always liberally coat the splines with Triple Guard grease prior to re-installing the gearcase. 
That restrictor was only used for a period of about three years and was gone around 1988. I have yet to see one come out of a pump and honestly never knew what they were for. By far the biggest restriction to flow in those engines is the grommets at the top of the water tubes. With any heat they melt and close up pretty bad. You have no indication of this as the overboard indicator looks like normal at an idle and all the way up to WOT. On any of the 15hp engines I purchase for resale I replace these before I ever sell the engine.


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## timsmcm (Jan 21, 2017)

Pappy that is the best advise you can give someone who owns an old omc 9.9 or 15 hp. That's solid advice.


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## doc1976 (Mar 22, 2017)

Pappy said:


> The small O-ring is used as a driveshaft seal and is placed in the groove just under the splines at the top of the shaft on driveshafts with the o-ring groove. Regardless, always liberally coat the splines with Triple Guard grease prior to re-installing the gearcase.
> That restrictor was only used for a period of about three years and was gone around 1988. I have yet to see one come out of a pump and honestly never knew what they were for. By far the biggest restriction to flow in those engines is the grommets at the top of the water tubes. With any heat they melt and close up pretty bad. You have no indication of this as the overboard indicator looks like normal at an idle and all the way up to WOT. On any of the 15hp engines I purchase for resale I replace these before I ever sell the engine.



so pappy, I understand there are two different styles of these grommets, and my model year should have the later and less desirable style. after a little reading im not quite sure on the proper way to install this style. any tricks for a more successful install?


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## Pappy (Mar 22, 2017)

They aren't exactly easy to get in place but they will go. 
As far as tricks go you can remove the rubber material that sticks up above the copper tube a bit. That will keep it from collapsing over the tube opening.


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## doc1976 (Mar 23, 2017)

sounds good. the ones that came out were actually in pretty good shape, weren't blocking the passage at all. took the powerhead off for ease of replacing t stat and head gasket and figured might as well go through things while its off.


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## Pappy (Mar 23, 2017)

Good deal. I do that with every one I buy before re-selling it. Better safe than sorry.


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## doc1976 (Mar 23, 2017)

as far as flushing, i was toying with the idea of using something like a CLR or similar to aid in cleaning out the water passages. some kind of pressurized adapter with a corrosion cleaning solution that i could fill the passages with and let sit for a bit and then flush out. Any thoughts? my only worry would be damaging any rubber or seals or anything it might contact.


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## Sinkingfast (Mar 23, 2017)

I have read several good outcomes using that method on several forums. Mix as for coffee maker cleaning. Flush with water after. You..or your motor might suffer a stroke if a chunk breaks off though...

I'd run it enough to fully open thermo as to not catch debris as might happen on a partly opened thermo. 

Thats all I's got on the subject.


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## Pappy (Mar 23, 2017)

A simple fresh water flush has been working for decades. If you do that and put your powerhead and gearcase back together using something like Tripleguard grease on the bolt threads or Tef-Gel plus spray down the powerhead with a WD-40 or something that should be all you need.


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## doc1976 (Apr 4, 2017)

Does anyone here know how long the water outlet tube should be? I have a feeling the one on my motor was damaged at some time and cut short. I wonder if this would cause any problems.


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## Pappy (Apr 5, 2017)

Doc, nobody here is a mind reader. List what issues you think you are still having for a better understanding by those who read this. 
Secondly....YOU can do the math on the water tube yourself. 
Measure from the edge of the exhaust housing down to the beginning of the water tube. 
Measure from the edge of the gearcase housing up to the water tube inlet on the pump. 
Take your two measurements and see how deep the tube enters the grommet. Pretty simple.


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## doc1976 (Apr 5, 2017)

Pappy said:


> Doc, nobody here is a mind reader. List what issues you think you are still having for a better understanding by those who read this.
> Secondly....YOU can do the math on the water tube yourself.
> Measure from the edge of the exhaust housing down to the beginning of the water tube.
> Measure from the edge of the gearcase housing up to the water tube inlet on the pump.
> Take your two measurements and see how deep the tube enters the grommet. Pretty simple.



I am talking about the water OUTLET tube from the motor. I got my answer though, someone before me cut more than 3 inches off the tube. I am guessing they bent or crimped it last time they had the power head off.


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## Pappy (Apr 5, 2017)

The outlet tube is pretty short anyway. No reason to cut it shorter as it really does not go anywhere. Still didn't mention what issue? Or did I miss that?


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## Pappy (Apr 5, 2017)

doc1976 said:


> sounds good. the ones that came out were actually in pretty good shape, weren't blocking the passage at all. took the powerhead off for ease of replacing t stat and head gasket and figured might as well go through things while its off.



You did not find a crimp or anything when you had the powerhead off and replaced the grommets as you listed above?


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## doc1976 (Apr 5, 2017)

yeah, it wasn't till I got things cleaned up that I noticed it wasn't even long enough to go into the little hole it it supposed to go into in the mid section of the motor. I also noticed a pinhole in the the incoming water tube as well. not sure if that was drilled from the manufacturer or not, still trying to figure that one out too. I am not currently having an issue, just working on the inspection phase of the job. I am asking questions here as needed as I go along if my other research doesn't give me answers


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## doc1976 (Apr 5, 2017)

oh, sorry. I guess a better answer to what my issue is, would be to reference this post which is about the same motor in regards to water circulation. Pappy, you offered help on this one too.

https://www.forum.tinboats.net/viewtopic.php?f=4&t=42711


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## Pappy (Apr 5, 2017)

That short one does not even need to be there....the water will find its way out if it were lost or not installed. Not telling you to take it out by any means but it is just a water dump.
The "Pin hole" is supposed to be there. It will spray the megaphone and inner exhaust.


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## doc1976 (Apr 6, 2017)

I kinda thought that's what the pin hole might be for, as far as the small tube is concerned, I've got a thing for using correct parts on an engine so I think I will replace it with a new one.


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