NS5B idle trouble

Aug 30, 2016
34
Hunter 23 Tyler
Hi all, working on my old Nissan NS5B, and was trying to get idle smoothed out, but it’s behaving odd... I turned adjustment all the way in, and backed it out only a fraction (any more than that, and it would roar and not come back down). I’ve attached a video of how it’s reacting. When I hit the gas, it takes forever to come down again.
Now, this is my first outboard, so bear with my inexperience. Oh, last thing, carb is brand new.
 
Nov 6, 2006
9,885
Hunter 34 Mandeville Louisiana
Couple of things to look at.. one would be an air leak at carb base or the fuel pump pulse drive.. other would be the spark advance.. too much spark advance will sound like that .. something with the linkage when carb was replaced?
 
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Jun 6, 2006
6,990
currently boatless wishing Harrington Harbor North, MD
Check the air filter. If it is dirty then the carb can need cleaning. Specifically the air jets in the intake before the venturi. Disassemble and blow out with air. Run into this all the time with chainsaws
 
Aug 30, 2016
34
Hunter 23 Tyler
Check the air filter. If it is dirty then the carb can need cleaning. Specifically the air jets in the intake before the venturi. Disassemble and blow out with air. Run into this all the time with chainsaws
Well, carb is brand new, and I cleaned filter at the same time...
I do need to look at the seal. I don't recall if it came with a new one when I installed it...
How do I check the spark advance on this motor? (sorry, I don't have a service manual)
 
Apr 27, 2010
1,236
Hunter 23 Lake Wallenpaupack
You can also post on the iboats outboard specific forum. I get a lot of good advice on my Honda 8HP there and they have a couple of pro mechanics who often give good advice, and these guys specialize in Nissan, Tohatsu, etc.
 
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Nov 6, 2006
9,885
Hunter 34 Mandeville Louisiana
spark advance... usually there is a mechanical linkage that advances timing when you open the throttle.. I am not familiar with that engine, but many/most two stroke outboards have that.. A quick look at a parts drawing and I see no such linkage for that engine, so the advance is probably electronic, programmed in the ignition module.. Chances are good that that is not the problem since it is making sparks. but do check all of its connections to be sure they are clean and tight.
 
Jun 8, 2004
10,024
-na -NA Anywhere USA
are you using ethanol gas and if so are you putting in an additive to combat the ethanol. Is the gas you are using ethanol or ethanol free? I use to be a tohatsu/Nissan dealer and you have the old two stroke. This is the first thing anyone should be asking.
 
Aug 30, 2016
34
Hunter 23 Tyler
are you using ethanol gas and if so are you putting in an additive to combat the ethanol. Is the gas you are using ethanol or ethanol free? I use to be a tohatsu/Nissan dealer and you have the old two stroke. This is the first thing anyone should be asking.
I honestly don't remember if it has ethanol in it or not. Will this affect the way it runs, or will it do damage in the long run? Right now, I'm just trying to get it running right. I'll be happy to change the gas before I actually head to water... If I need to fix the gas now, how do I accomplish that?
 
Aug 30, 2016
34
Hunter 23 Tyler
Just did some googling, and it looks like the biggest issue is the water buildup and hoses that aren't happy with the ethanol. Most outboards seem fine with e10, just not 15. I also read that many stabilizers are not legit.

Bleh, once this weather clears up a bit, I am going to remove carb, clean it all out, clean out gas tank, and replace the seal. -- and pray.

https://www.westmarine.com/WestAdvisor/Busting-Ethanol-Fuel-Myths
http://www.ybw.com/forums/showthread.php?461159-Ethanol-E10-fuel-in-a-2-stroke-outboard
 
Apr 27, 2010
1,236
Hunter 23 Lake Wallenpaupack
If you can access the low speed jet by itself, try that - it may just work if it is the culprit. You may also want to change the fuel hoses on the engine if they are old, possibly also including the ones from the fuel tank to the engine (I assume an external tank). They can evidently shed small particles as they age.
 
Jun 8, 2004
10,024
-na -NA Anywhere USA
Corn syrup clogs up jets in the carb. I would take down the carb and clean out the jets in particular. That generally was the culprit using ethanol gas. Use only ethanol free gas in any small engines to include lawn mowers
 
Aug 30, 2016
34
Hunter 23 Tyler
Ok. Apologies necessary. I found the issue:
gasket.png
What's wrong with this picture?
I can't believe I didn't see this.

So after I fixed this, she purrs like a kitten:

I noticed the water was only dripping out (and I just changed the impeller), so I cleaned out the pee hole with a wire... Wow what a difference!
 
Aug 30, 2016
34
Hunter 23 Tyler
Thank you all very much for your help on this.

My next and final step on this is to make the tank external. This old metal tank is shot. I need a U shaped turn to make the connection to the carb work.

IMG_6994.JPG

If anyone has any ideas or links, let me know. The external kit for the NS5B is pretty pricey for what it is, I'm hoping to find a cheaper solution.
 
Nov 6, 2006
9,885
Hunter 34 Mandeville Louisiana
Good that it was an easy one !
Go on line or Bass Pro for external tank and hose primer assembly.. Local hardware for brass fittings/nipple adaptors for making the "U" bend and for new inside cover fuel hose.... Extend hose out of cowl through old hose connection port a few inches; add quick disconnects.. ya done.. New low permeation tanks are a lot more expensive than they used to be so you'll have around $100 invested in the external tank conversion before you are done..
 
Last edited:
Aug 30, 2016
34
Hunter 23 Tyler
Good that it was an easy one !
Go on line or Bass Pro for external tank and hose primer assembly.. Local hardware for brass fittings/nipple adaptors for making the "U" bend and for new inside cover fuel hose.... Extend hose out of cowl through old hose connection port a few inches; add quick disconnects.. ya done.. New low permeation tanks are a lot more expensive that they used to be so you'll have around $100 invested in the external tank conversion before you are done..
Yeah I noticed those tanks aren't cheap. I also found this:
https://www.hopgoblin.com/1-4-inch-stainless-steel-u-bend-p/kg87634.htm
for the bend. I think I'll grab this, as it will cost 4x that amount to rig that at the depot. As much as I'd love quick connects between it all, I think I may run the hose straight from the motor to the tank, and put quick connect there at the tank. Thoughts on this?
 
Apr 27, 2010
1,236
Hunter 23 Lake Wallenpaupack
It is interesting that a blocked telltale caused idle problems. I thought they just let water trickle past the cooling circuit and that if blocked the cooling system still worked as intended and did not cause any back pressure.
 
Aug 30, 2016
34
Hunter 23 Tyler
It is interesting that a blocked telltale caused idle problems. I thought they just let water trickle past the cooling circuit and that if blocked the cooling system still worked as intended and did not cause any back pressure.
LOL, not the blocked pee port, but the dropped carb gasket... Take another look:
IMG_6987.JPG