Nissan 9.8 4-stroke Carburetor

[JDusza]

Working on a new-to-me Nissan 9.8 hp 4-stroke. Not sure of the year. The model is NSF9.8A3 3V2-1. It's very clean and hasn't run in a couple years. Last few times out the owner complained of erratic and rough running. They thought it might have had some bad fuel and that the carburetor needed cleaning.
I took it out and found the fuel line leaking at the in-line fuel filter. The filter is cracked and sucking air.
I replaced the filter and low and behold, there is another problem!
Raw fuel is now literally dripping off the carburetor. I guess the fuel pump is working.
I could use some advice on what year this unit is, where I can find an exploded view parts list and what might be wrong with the fuel delivery system to make it leak so bad.
Thanks,
J

 

[pvanv]

Year is irrelevant; model/serial is critical. The needle is not seating. Clean the carb properly and check float height. You can get the SERVICE MANUAL - NISSAN - 8/9.8A3 4STR

Part # 003N210561
List Price (MSRP): $40.00

from any dealer, including several forum members -- even me... (sorry, not directly from iBoats). The owner's manual is available for free download from nissanmarine.com.

 

[JDusza]

I am surprised. This is also the first Nissan I have worked on. Are they good engines or is this a harbinger?
I should also tell you that after a few minutes of running at the dock, the cylinders build up enough fuel to stop the recoil starter from spinning the crank. Stalls out and you can't even pull it over. If I pull the plugs and spew the gas with the recoil and reinstall the plugs, I have a chance to pull the engine over. Not impressed so far.....Nissan....
Thanks,
J

 

[Sea Rider]

Well that's the issue of badly seating any engine brand model for sooooooo long time period. There are procedures for doing so properly. Previous owner was real careless doing so and passing problems to you.

Minimum you should do is have a extensive carb clean, inspect any internal carb parts, fuel pump parts that could have been damaged inisde, change oil + filter, lower unit gear oil and plugs, check impeller cond, throw previous gas leftovers if any left on tank, use fresh fuel. That's a excellent HP model, beats any 8 any time, any day, any place. When fully serviced, will start liking it.

Happy Boating

 

[pvanv]

If you are flooding so much that fuel is dripping from the carb, it's surprising it will even run... and of course that gas will get into the combustion chambers. Service the carb, install a new wp kit, change oil (do not overfill, use non-synthetic FC-W 10w-30) and change LU lube, The 9.8A3 Tohatsu is the absolute best in its class. I own one personally, and service a lot of them. Almost indestructible if reasonably cared for -- which yours wasn't.

 

[JDusza]

Thanks for the support. It's good to hear that this will be a good little engine. I am in Evinrudes and Mercs all the time but this is new to me.
I am also surprised it is running. I can't say for certain where the gas is leaking from. It is very tough to see in there. It is either at the fuel line inlet nipple or out of the carburetor. I inspected and reseated the fuel line last night without positive result. Sounds like I'll be okay with a little more patience and a rebuild kit. By the way, which carburetor kit is for this engine? I talked to marineengine.com and they couldn't positively ID the right kit for me. I'm calling iboats now. This is a NSF9.8A3.
I have to say that when it is running it is very fast. At first, I found the steering incredibly loose and with this power, very dangerous; toss you right out of the boat. I tightened up the steering and am back in control. And, it does look like carburetor removal will be pretty easy. Two ten millimeters straight out the front...
Thanks for the help and support! I'm looking forward to working on this now!
J

 

[pvanv]

3V1871220M CARBURETOR REPAIR KIT MSF8/9.8A $52.64 available from any dealer... even several forum members, including me. If you are careful and lucky you can re-use the 2 carb base gaskets and the thermal spacer. Pull the air silencer and carb as a unit. Then disconnect the fuel line, and set the silencer aside. Fully disassemble the carb (including the emuksion tube nozzle and both jets... soak all non-rubber bits at least 4 hours in carb dip and then blow all out with generic carb spray. You may or may not need the kit, but if the needle is flooding, best to install it.

 

[JDusza]

Thank or hanging in with me, Paul. Sad news... I might be ready for a dealer. I cannot find the source of this leak and I'm at wits end.
I went into the carburetor today, without the kit, just to see of things were corroded or sticky. I found a pretty clean interior with all parts seemingly working well. The float is mechanically linked to the needle so the needle cannot stick. Parts are clean, jets are open. I tried the float valve by blowing into the fuel inlet holding the body right side up and up side down. Air flows right side up and does not flow upside dowm. So, I think the valve is working. I also tried a new hose clamp on the fuel inlet to ensure the hose connection isn't leaking.
I'm beginning to wonder of the brass fuel inlet tube junction into the aluminum housing is the problem. I also tried a little gasket sealer around the bowl seal to see if I could affect the leak. No success.
The unit floods so bad the spark plugs drip. You can shake fuel off them. Now the engine won't even start because the cylinders are soaked.
The money I'm going through may be better spent with a certified tech. I know that'll double or triple the cost, but, right now I'm shooting in the dark.
J

 

[pvanv]

The correct fuel hose almost doesn't need a clamp. Maybe someone used a piece of incorrect fuel line? Still, that would just make a mess OUTSIDE the motor. Is the brass block-off plug (goes in the same bore as the slow jet) missing? If the bowl gasket failed at the fuel inlet area (the fuel routes through to the upper casting at that point), that could allow fuel to leak both inside and outside, resulting in both a mess and severe flooding.

 

[JDusza]

I think all the parts are correct. The interior doesn't look like it's ever been serviced. I know the carburetor was taken off last year by another and cleaned. I don't know if any parts are missing. I can't imagine they are. Everything LOOKS great.
The leak is in the rear in the vicinity of the fuel hose. Raw fuel drips off the carburetor housing and down the fuel hose and drips into the lower housing.
It doesn't leak immediately at start-up. It takes a few seconds like the system is filling. After a few seconds of running, here it comes!
The fuel line looks good, no splits or cracks, nice and pliable, can't see any holes. It should not be leaking. Aside from looking and feeling right, right now it has both the original hose clamp and a ty-wrap strangling it. I can try another hobby hose I have and see if that changes anything.
The gasket seal I used should have at least changed the way the unit leaked. Even if it didn't stop, it should have changed.
Maybe I'll blow the short money on the rebuild kit and see what happens with a new float (maybe the float's dead?) and a new bowl gasket. I can try sealing the brass inlet tube with nail polish. If it still leaks after the kit, I'll go pay the oracle.
J