Nissan NS8B Main nozzle removal + bizarre intermittent spark on one side

CaptainYowza

Recruit
Joined
Feb 13, 2009
Messages
4
How in the name of foot-long chili dogs does one get the main nozzle out of the carb? Got the two jets out fine, but all I can do with the nozzle is push down the protruding top in the carb throat. The only solution I can think of is to shoot compressed air in the right place while covering up other right places, but there's gotta be a better way. Cursing at it certainly didn't work. It's properly soaking now, fully disassembled exceptin' fer the nozzle.

And here's the baffling one....first some history on the motor.

It was bought new, broken in properly, and used a handful of times before sitting for many years. Dad gave it to me, I did routine maintenance (carb kit, fuel pump, impeller) and have now run her happily for 2 years on a spiffy, unique 1957 15' Crestliner ("Ward Cleaver's Wet Dream"). Great motor, when warm it would start with a gentle 4" tug on the rope.

Last week, way back in the swamp (of course) at Caddo Lake, TX, I all of a sudden had half a motor and she smelled rich. I knew it was bad spark quickly. However, I could often coax, eventually, normal performance by feeling for the right moment and then busting thru with the throttle. Hard to describe.

Back at home lake got similar results and a timing light confirmed good spark on one cable and intermittent (no spark - irregular spark - normal spark) spark on the other. Since I love spare parts and the motor is about 20 years old, I had no qualms about replacing the ignition system on a motor I got for free. If the thing peters out on us at the wrong moment, we can end up deader than fried chicken (Houston Ship Channel, etc.). There's nothing like doing the Elmer Fudd Yank when a container ship is bearing down on you. And, I've seen enough bad coils that looked fine on a multimeter to not trust amateur testing all that much.

After carefully checking over everything on the near-pristine motor (she's just now finished the original gallon of oil), I replaced the exciter, CD unit, and the right NGKs. The exciter wires near the assembly were strangely "gooey", but it otherwise appeared unremarkable.To my astonishment, I got the same intermittent spark and harder starts on the hose in the driveway. Like with the carb nozzle, cursing at it helped none.

Did an obligatory compression test and results were as expected - 53 psi each (spec = 57). Buttoned her back up and she ran perfectly, still on the hose. Timing light normal both cables. Yeah, it's an intermittent problem, but after it began it always sparked poorly at idle speed. I'd have to get her running a bit, then catch the sweet spot to get it firing right and a smooth ride back to the dock would result.

So, I'm hopeful about the normal idle on the hose, but we're hitting the salty stuff next week and I really need to get this ironed out. After I get the carb back on I'll do another driveway test and a lake test Friday, but for now does anyone have a clue what the problem might be? My jaw about hit the floor when the ignition system replacement didn't set things right, and the apparent improvement after the compression test has my brow furrowed even more.

The only thing I can think of is to check for a nice, clean, paint-free ground. Otherwise I'm stumped. Even if the problem does not return, I'm baffled as to why it wouldn't run right for a half-hour amid a bunch of tinkering and head-scratching after the parts replacement, then it's suddenly find after compression testing.

The world sure is a big pain in the hindquarters sometimes.
 

pvanv

Admiral
Joined
Apr 20, 2008
Messages
6,509
Re: Nissan NS8B Main nozzle removal + bizarre intermittent spark on one side

Sometimes a warmer carb casting will expand a bit, allowing the nozzle out. Otherwise, patience wins.

Because of the siamese coil, if one is firing, the issue is typically a plug cap or wire, or defective plug.
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Re: Nissan NS8B Main nozzle removal + bizarre intermittent spark on one side

If you could finally remove the stuck main nozzle let me know the procedure, been tryining to remove same from a 2006 engine with no positive results whatsoever, have tried all removing methods. Seems the carb and myself will need to live with it forever and ever, amen!! You've made a costly parts replacement guessing, forgot ignition coils, which should have been the one to replace and test first as this part costs much less than a CD.

Happy Boating
 

CaptainYowza

Recruit
Joined
Feb 13, 2009
Messages
4
Re: Nissan NS8B Main nozzle removal + bizarre intermittent spark on one side

Paul, thanks a million for your fast response. I was gathering a junk saucepan and the ol' Coleman stove when I got an idea that I think Sea Rider will like.

I took a piece of insulated multi strand copper wire thin enough to fit thru the nozzle and ran it from the bottom of the nozzle into the carb throat. Then I grabbed the wire with hemostats in the carb throat, pulled it out of the carb and tied a single overhand knot at the very end. Take the opposite end of the wire on the float bowl and gently pull it until the knot hits the top of the nozzle, then pull straight and the nozzle popped right out.

The wire was one side from a 12v cigarette lighter plug I had laying around. This worked perfectly and is very gentle on the carb.

I have normal spark on each side now, just like last night, but still on the hose. I swapped my 8hp jets/nozzle for 9.8hp to try and scam up a little more mojo from the ol' gal. She started right up and is a little chuggy, but finally got a tach for it and the idle was at 690 rpm instead of the 900-950 in neutral my Nissan service manual calls for. I bet after a lake test Friday and some adjustment she'll be fine. The fact that she held idle at all under 700 rpm is a great sign.

Good luck, Sea Rider. I like Peru
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Re: Nissan NS8B Main nozzle removal + bizarre intermittent spark on one side

Capt. Yowza,

Thanks for the removal tip, brilliant idea, next time stripping my carb down will try, for the moment just squirting 1/2 carb cleaner through the nozzle to keet it clean. If your engine is a 2 strokes, swaping jets and nozzles is not the way to go. All (3) 6.8.9.8 B series engines use it's own carb model, including propietary jets and nozzles sizes for each model. Although you can swap jets and nozzles from the 9.8 into the 8 carb, keep in mind that each carb has different fuel passages sizes. More HP, more fuel passage diam.

The 9.8 runs at 950 RPM in neutral and 750 in gear and load, one thing is testing on a hose, other installed and running on a boat. Probably will need to place back original 8 jets and nozzles to perform as factory stated. If wanting an update from 8 to 9.8 will need to buy a new 9.8 carb. You could have hidden electrical issues inside Ignition Coil, like heating up under load and misbehaving.

Thanks for your kind words.

Happy Boating
 

pvanv

Admiral
Joined
Apr 20, 2008
Messages
6,509
Re: Nissan NS8B Main nozzle removal + bizarre intermittent spark on one side

Good technique to pull the emulsion tube nozzle!

Put your original carb parts back in the carb! If you swap in larger jets, etc, you will way too rich, and will drown in fuel to the point of fouling plugs. Depending on serial number, the 8B and 9.8B are different blocks, in addition to having different carbs, so even swapping to the 9.8 carb will not help you gain hp.

The 8B was a sweet motor just as it came from the factory; we have a few still in service, and they are excellent as is.
 
Top