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Nissan NS5B 5hp Fuel Tank replacement

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Myke66

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I bought an NS5B off Facebook and it was demoed, running, looked good. Took it home and noticed a few issues. The main was the fuel tank cap threads were stripped and so were the threads on the tank, reading online this seems common so I had a few questions if anyone can help.

Is there anything else needed aside from the tank and cap to do a swap?

Will the fuel cock transfer to the new tank? Anything I should know before removing?

I noticed the fuel cock rod was ziptied to the fuel cock, any suggestion what needs replacing there? It still works using the fuel on/off knob. Was it maybe to help it from slipping?

There was also a broken fuel tank rubber mount, I wanted to replace that too.

Thanks
 
You will need the tank, cap, whichever mounts, and the fuel cock takes a special clamp, not available separately from the valve. A good UV resistant tie wrap should be OK:
002-21005-6_FIG13.jpg
Item 13 is a piece of tubing:
353725441MTUBE$2.98

 
pvanv said:
You will need the tank, cap, whichever mounts, and the fuel cock takes a special clamp, not available separately from the valve. A good UV resistant tie wrap should be OK:
View attachment 21113
Item 13 is a piece of tubing:
353725441MTUBE$2.98

Click to expand...

Tyty for reply, so I will be able to move fuel cock over to new tank -- is there a certain way to remove it? I don't want to break it by twisting or pulling the wrong way.
 
Myke66 said:
Tyty for reply, so I will be able to move fuel cock over to new tank -- is there a certain way to remove it? I don't want to break it by twisting or pulling the wrong way.
Click to expand...
Just release the clamp and pull it out.
 
pvanv said:
Just release the clamp and pull it out.
Click to expand...

Fuel tank and mount replacement went smooth today, thanks for the help. One last question, should the motor be stored with the vent open or closed? And should the motor be run with the vent open or closed?
 
pvanv said:
You can dl a copy of your manual from tohatsu.com
Click to expand...

Thank you, I did do that and read it over.

I ran the motor today for the first time on the boat and it runs okay between 1-40% throttle but once it hits 40%+ the RPMs start surging and it loses power, I am assuming it hits rev limiter and I back down the throttle to bring it back under control. I have a tach that you wrap a wire around the spark plug and reads about 4k rpm when it surges to 6k+ RPM.

I did some research into the issue and I'm reading it could be related to fuel delivery. I looked up the parts for the on board fuel tank because I wanted to try changing the fuel filter to see if that helps but the parts catalog doesn't show a fuel filter for the integrated fuel tank.

Is there a fuel filter supposed to be on the integrated fuel tank (there is on mine) and if so is that a good starting point to fixing this?

Thanks

edit: Here are pictures of what I'm referring to, I put an arrow where the fuel filter is on mine and where it shows on the separate fuel tank.
fuel filter.jpgfuel filter 2.jpg
 
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My original though was it was related to the prop and not fuel related. When it surges there it feels like there is no load on the prop, like its almost in neutral and when i lower the throttle and the RPMs come back down you can feel the thrust engage again. I was also able to run it at full throttle for a while with no RPM surging but then it started again which had me back to thinking fuel. Want to give as much info as I can. I also took a video of it happening.

edit: Last update, spoke to some other folks about this and they mentioned it could be the rubber bushing in the prop. The prop looks aftermarket and feeling I get when it "surges" is its as if there are no blades on the prop. I think "surge" brings up a lot of google hits on fuel issues so I started there but now i'm thinking maybe a new prop is in order.

I would still like to know if there is supposed to be a fuel filter on the integrated fuel tank or if that should be remove as its rubbing on the fuel cock rod causing wear.
 
Last edited:
Myke66 said:
My original though was it was related to the prop and not fuel related. When it surges there it feels like there is no load on the prop, like its almost in neutral and when i lower the throttle and the RPMs come back down you can feel the thrust engage again. I was also able to run it at full throttle for a while with no RPM surging but then it started again which had me back to thinking fuel. Want to give as much info as I can. I also took a video of it happening.

edit: Last update, spoke to some other folks about this and they mentioned it could be the rubber bushing in the prop. The prop looks aftermarket and feeling I get when it "surges" is its as if there are no blades on the prop. I think "surge" brings up a lot of google hits on fuel issues so I started there but now i'm thinking maybe a new prop is in order.

I would still like to know if there is supposed to be a fuel filter on the integrated fuel tank or if that should be remove as its rubbing on the fuel cock rod causing wear.
Click to expand...


Couldn't edit previous post any longer, here is a picture of what my fuel line looks like and one that I found a picture of on the net.

My Fuel line that has a filter

fuel line.jpg

Reference I found online without a filter
fuel line2.jpg
 
The fuel cock for the integral tank has a fine mesh strainer filter, unless it was removed.
You likely have a spun prop hub.
 
pvanv said:
The fuel cock for the integral tank has a fine mesh strainer filter, unless it was removed.
You likely have a spun prop hub.
Click to expand...

Thank you for the confirmation, I've ordered a new prop and will inspect the fuel cock when I change out the fuel line. I assume it will be on the outside of the post that's inside the tank.
 
pvanv said:
The fuel cock for the integral tank has a fine mesh strainer filter, unless it was removed.
You likely have a spun prop hub.
Click to expand...

unfortunately this did not fix the problem, I changed the prop today and took it out and experienced the same issue where it will shoot up its RPM under higher throttle. I'm wondering if it could be pulling air from the surface somehow, it is a 20-in long shaft on a 21-in transom. I noticed that the deeper it was the less issue I had with the RPM shooting up, although it did still happen. Even when the RPM wasn't shooting up it was very variable as you can see in the video below.

I did not get a chance to remove the fuel filter that was on it, but after I got home I pulled the fuel cock and it did not have a screen filter.

It did perform better with a new prop however. Below is a video I took of the performance while it wasn't having the RPM shooting up but still chugging. I'm going to replace the fuel line and I'm assuming I will need to replace the fuel cock, but I'm doubting this is going to fix the issue.

https://youtu.be/GAmmtkOs-bU
 
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Sounds like you might be ventilating the prop. It should be deeper. Only other thing is to VERIFY that the shifter is going all the way into reverse.
 
pvanv said:
Sounds like you might be ventilating the prop. It should be deeper. Only other thing is to VERIFY that the shifter is going all the way into reverse.
Click to expand...

Is there any way to get this any deeper aside from using the lowest setting on the adjustment rod and having it in the fully down position?

This was in Forward, should I still check reverse?
 
Thank you for all of your help, I have decided to try and sell this motor and look into a bigger one. It was fun fixing it up and I learned a lot about outboards in the process but I see no easy way of making this work economically at this point. I hope to find a 9.9 with a long shaft for my next attempt.
 
pvanv said:
If you get ann ultra long 6 or 9.8 sail pro, that should take care of everything.
Click to expand...

Great to know, I was happy to learn the motor was working well so I felt good selling in favor of a bit more hp. I am looking into the 9.8hp Tohatsu MFS9.8BL.
 
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