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Nissan 4-stroke 6HP (NSF6BS) Water/Exhaust Question

C

Chris_FL

New member
Hello,

My name is Chris and I live in Tampa, FL. I signed up to ask a question regarding a Nissan 4-stroke 6HP (NSF6BS) outboard that I purchased for my son a couple of weeks back. The outboard is a 2006 or 2008.

We have used the outboard a couple of times now and everything seemed fine. After use, we flush it by connecting a garden hose and letting it run on a wooden stand for a couple of minutes. Whenever we connect the garden hose, the little pee hole starts showing water. So far so good.

This weekend I noticed, that while running on the stand, not only did we have water coming from the pee hole, but also from the three little rearward facing openings/holes just on top of the cavitation plate. I had never seen that before. The water coming from there is really hot and it seems to be mixed with the exhaust gases. I removed the rubber grommet on the midsection and I can see the gear-shift-rod and water running inside the mid section exhaust. My question is, if that is normal. So when I flush, I see water coming from the pee hole, the three holes on the back just above the cavitation plate and little through the prop.

It just seems strange that the entire midsection, including the axle and the gear shift rod are under constant water and exhaust gas.

So far, I have replaced the thermostat and the thermostat gasket and replaced the drive shaft gasket. Now I am at a loss where all this water makes its way into the midsection and the exhaust. Could someone help me, please?

Here are some pictures:

38810363zb.jpeg


38810364nn.jpeg


38810365ej.jpeg


38810367hk.jpeg
 
Of course that is normal. 99% of cooling water travels out with the exhaust. The 1% that goes out the telltale only shows that the cooling system is pressurized. Those weep holes allow the water to drain so trapped water doesn't stay there and freeze in colder weather.

Why did you change the thermostat? Was it overheating? Probably not, so you threw your money away.
 
Paul, thank you very much for your reply. I guess I never noticed the weep hole activity and only saw the telltale. I appreciate your explanation. And you are correct, changing the thermostat was probably unnecessary maintenance. But I have learned so much about the engine in the process, that it is totally worth it.

Please allow me to follow up with two questions: When flushing on a stand with a hose connected, is there any noticeable/visible change in the water flow depending on whether the thermostat is open or closed? It seems to be the same through all holes, no matter if the engine is running and/or the thermostat is open or closed. Secondly, do you flush on the stand with the hose with the engine running or not?

Thank you for your time and help,

Chris
 
Thermostst open or closed should make no difference.
OK to idle. You are supposed to block off the water inlet per your owners manual.
 
Thank you, Paul. I downloaded a manual today and will block the water inlet in the future.

The manual also says to remove the prop every time I flush with the hose.
Could you enlighten me, if this a technical/mechanical requirement or a safety concern?

Chris
 
Paul, may I ask you one last question regarding this motor, please?

As preventive maintenance, I am replacing the impeller and the metal Water Pump Case Liner.

Could you tell me if there is a trick to removing the old Water Pump Case Liner from the Water Pump Body?
I wanted to check with you first, so I have not tried to remove it with much force yet, but it seems to be quite tightly in there.

Thank you very much

Chris

PS: For everybody else, here is a picture of the upper Water Pump Housing with the metal Liner in it, that I am trying to remove:

38864179wv.jpeg
 
Definitely tine for a new cup. Sometimes they are quite stuck. When installing, I usually use grease or antiseize so that isn't a factor next time. You can warm the housing with a heat lamp. Otherwise, you will end up digging it out. If you damage the housing too much, you will end up replacing that as well.
 
Just completed the impeller change. Got the liner out with a bit of force.
The inside of the plastic casing (behind the liner) had some slight damage (heat I think), but it still works fine.
I'll replace the upper housing during the next impeller service.

And it's working just fine.

Thank you again, Paul!
 
Hi Chris! when you had the grommet on the side out, was water coming out of there, also? I just replaced the impeller on my Nissan/Tohatsu 5hp and fear I've reassembled it incorrectly. I did not think that chamber should have water in it, but it sounds like from your experience and feedback-received that it's normal. I do get glow from the tell-tale and from a few tiny holes toward the prop.

I don't want to disassemble - it took a while to get it lined up correctly!
 
Hi smosh! Yes, when I removed the 1 inch grommet on the side of the drive shat housing, I had exhaust gas and water coming out of there. I think Paul also said that this is normal, and when you have a look at the water's pathways while replacing your drive shaft gasket (I did), you will realize that this is the "normal" way for cooling water and exhaust gases to exit the motor. They then push downwards to the three holes (under water) above the cavitation plate. I was initially irritated when I removed the grommet and looked inside the drive shaft housing. I saw the drive shaft and the gear rod and could not imagine this area being "wet" all the time from cooling water. But given that the three holes at the cavitation plate are under water anyway during operation, of course they also let water in when the engine is not running. So apparently this area is designed to work with water. I hope this helps. Chris
 
Chris_FL said:
Hi smosh! Yes, when I removed the 1 inch grommet on the side of the drive shat housing, I had exhaust gas and water coming out of there. I think Paul also said that this is normal, and when you have a look at the water's pathways while replacing your drive shaft gasket (I did), you will realize that this is the "normal" way for cooling water and exhaust gases to exit the motor. They then push downwards to the three holes (under water) above the cavitation plate. I was initially irritated when I removed the grommet and looked inside the drive shaft housing. I saw the drive shaft and the gear rod and could not imagine this area being "wet" all the time from cooling water. But given that the three holes at the cavitation plate are under water anyway during operation, of course they also let water in when the engine is not running. So apparently this area is designed to work with water. I hope this helps. Chris
Click to expand...

this helps -so- much, thanks! I thought maybe I didn't seat the elbow correctly in the impeller housing. It struck me as odd it was wet with all the linkage and all in there. But there's no gasket or seal between the lower unit and the shaft anyway, and the thing's in the water a lot.

ran it for a while after I saw this last night: so far, so good. Doesn't like to return to idle after revving, but hopefully just some easy adjustment vs. carb rebuild/replace.
 
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