1992 18hp Nissan carb issues...

[dfrants]

trying to repair a 1992 2-stroke 18hp Nissan. Model number NS18C2. She leaks fuel through the carb and needs a new float needle. when I go to look up the part number it just shows "obsolete" and doesn't give the part number. Anyone happen to know the number and where to order one? Also, whoever worked on this before me has the rich/lean screw turned almost all the way out. Whats the recommended number of turns out from lightly seated for a starting point?

 

[pvanv]

Yes, it's obsolete, and generally NLA. There were two different carbs used, depending on serial number. One had a round bowl, and the other an octagonal bowl.
For serials up to 47610:

350031400M

VALVE SEAT ASS'Y-NO LONGER AVAILABLE

For serial numbers above that:

398031400M

VALVE SEAT-NO LONGER AVAILABLE

Only thing you can do is try to find something similar at a motorcycle or NAPA shop from a different application. Even the complete carb is NLA.
Pilot screw adjustment typically starts at about 2 turn out, then adjust from there... but it really doesn't matter until after you get the fuel level correct.

 

[dfrants]

no luck with the float valve needle I ordered... way too big. Got the motor to run and idle without dying out with the old parts but there is unburned fuel coming out of the exhaust at trolling speeds. Would that be from a misadjusted float?(besides a worn needle tip). It doesn't leak fuel from the front of the carb. I checked for spark and each cylinder has a good blue snap. And compression is over 140psi in each hole...

 

[Sea Rider]

Which needle model or HP did you ordered that was too big ? Can you measure current faulty needle valve length and diam ?

Happy Boating

 

[dfrants]

the one they ordered for me has a tohatsu part number 3E3-03147-0. the needle I need looks just like it but is skinnier.

 

[Sea Rider]

Why are you trying to replace a needle valve ? is the tip not round & pointy, it's square ? Post a pic to have a look. Have never replaced a single needle valve in any of my OB's ever...

Happy Boating

 

[brahart]

trying to repair a 1992 2-stroke 18hp Nissan. Model number NS18C2. She leaks fuel through the carb and needs a new float needle. when I go to look up the part number it just shows "obsolete" and doesn't give the part number. Anyone happen to know the number and where to order one? Also, whoever worked on this before me has the rich/lean screw turned almost all the way out. Whats the recommended number of turns out from lightly seated for a starting point?

Hi Dfrants! I am coming across this same issue as of today in 2021! What did you eventually get? do you have a part number, maybe a link for a new float needle/ valve. Thanks!

 

[dfrants]

Hi Dfrants! I am coming across this same issue as of today in 2021! What did you eventually get? do you have a part number, maybe a link for a new float needle/ valve. Thanks!

I got lucky and found a dealer that had one in a bin. Part no. 3E3-03147-0. Charged me $32 for it, good luck.