Nissan 15hp 2 stroke Problems

[Technologic80]

I bought a Nissan 15hp, model #NS15B2 a few months ago... been using it on my 10' inflatable.

Lately when hot, the thing does not want to get up and go. It sputters and acts like its having fuel starvation or something. I changed the fuel filter, ran new gas through it, and have been using West Marines premium TCW3 oil at a 50:1 ratio. No change. However, when the engine is cold (just started) it flies up on plane and there is no sputtering at all.

There is water and exhaust coming from the triangular port in the rear of the outboard. I did not notice any coming from the 'telltale' hole though.

Does this sound like an overheat situation? And if so, any tips on changing the impeller?

 

[pvanv]

Re: Nissan 15hp 2 stroke Problems

Could be a number of things, even a cd or coil that is failing hot, but working cold. See if you can clear the telltale by pushing a stiff wire or monofilament into it while the motor is running... might dislodge some debris in there. Yes, it could be running too hot. If you don't know for sure that a wp kit was installed recently, it wouldn't hurt. Part # 362873220M $48.27. Also check the fuel pump, as it might be marginal. Full data is in the Factory service manual, available from any dealer, including me.

 

[Technologic80]

Re: Nissan 15hp 2 stroke Problems

Could be a number of things, even a cd or coil that is failing hot, but working cold. See if you can clear the telltale by pushing a stiff wire or monofilament into it while the motor is running... might dislodge some debris in there. Yes, it could be running too hot. If you don't know for sure that a wp kit was installed recently, it wouldn't hurt. Part # 362873220M $48.27. Also check the fuel pump, as it might be marginal. Full data is in the Factory service manual, available from any dealer, including me.

Thank you for your reply!

Would you be so gracious as to post, or PM me (or e-mail) the directions on diagnosing the CD or coil? Also, the directions on replacing the impeller if thats not too much to ask for!

I will try to stick a piece of strong metal up the telltale hole tonight, after I get home from work (5pm) and post back my results.

 

[pvanv]

Re: Nissan 15hp 2 stroke Problems

After you get your Factory service manual, the whole table of resistances will be available to you. Since the manual is copyrighted, it's not available online. You can get one at any dealer, including me. Ask for Part# 003-21035-1 $44.17

The wp kit is installed just like any other OB wp kit. Don't do just the impeller -- do the whole kit. Much better results.

 

[Technologic80]

Re: Nissan 15hp 2 stroke Problems

Ok yesterday I replaced the impeller - it did have all of its vanes, but the impeller was dry rot and cracked in several places, Im sure it was just a matter of time before the vanes started breaking off!!

Replaced the impeller and didnt have the pee stream, come to think about it, I havent ever had the pee stream but water and exhaust always came out of the exhaust port. Took a paper clip and unclogged the pee stream - water started coming out immediately. Score!!

However, Im still having the sputtering problem, only when hot and only when on plane for a while, maybe after 15 minutes of operation, if I come off plane and go to get back on plane it sputters very badly for a few seconds before it gets back up. It feels like its misfiring, like an old car would if the aged plug wires got wet. Funny thing is, it does this randomly. It may sputter and struggle to get on plane on a trip, and only do it 5 out of 10 times. All of the other times, it GOES. And when it goes, man that 15hp really goes.

Thinking of replacing the spark plug wires as a start. Spark plugs (NGK) are brand new. Has anybody else had their spark plug wires go bad? Could this be a coil or CDI too?

 

[pvanv]

Re: Nissan 15hp 2 stroke Problems

Ok yesterday I replaced the impeller - it did have all of its vanes, but the impeller was dry rot and cracked in several places, Im sure it was just a matter of time before the vanes started breaking off!!

Replaced the impeller and didnt have the pee stream, come to think about it, I havent ever had the pee stream but water and exhaust always came out of the exhaust port. Took a paper clip and unclogged the pee stream - water started coming out immediately. Score!!

However, Im still having the sputtering problem, only when hot and only when on plane for a while, maybe after 15 minutes of operation, if I come off plane and go to get back on plane it sputters very badly for a few seconds before it gets back up. It feels like its misfiring, like an old car would if the aged plug wires got wet. Funny thing is, it does this randomly. It may sputter and struggle to get on plane on a trip, and only do it 5 out of 10 times. All of the other times, it GOES. And when it goes, man that 15hp really goes.

Thinking of replacing the spark plug wires as a start. Spark plugs (NGK) are brand new. Has anybody else had their spark plug wires go bad? Could this be a coil or CDI too?

Exhaust from the telltale is bad... Means you aren't getting cooling water. Since that's fixed now, you may be OK, but you may have already overheated so severely that you did other damage. Go through the carb thoroughly. Always replace the entire wp kit when servicing the water pump. Your symptom could be a number of things -- almost anything -- but the carb is the most common area to check first.

 

[Technologic80]

Re: Nissan 15hp 2 stroke Problems

Exhaust from the telltale is bad... Means you aren't getting cooling water. Since that's fixed now, you may be OK, but you may have already overheated so severely that you did other damage. Go through the carb thoroughly. Always replace the entire wp kit when servicing the water pump. Your symptom could be a number of things -- almost anything -- but the carb is the most common area to check first.

Bahhhh! Its like no matter what I say on this big internetz, I always leave out a detail! Lol. I should clarify that a water spray has always come out of the exhaust port and what I assume to be actual exhaust, but never just exhaust gases alone. It always spat water, just never out of the weep hole. The water that came out of the exhaust port was never HOT either, just warm, even before I replaced the impeller. Exhaust has never came out of the telltale.

With that being said, I will turn to the carburetor for answers. I bought a SELOC manual last week which aided me in the impeller replacement greatly.

 

[Sea Rider]

Re: Nissan 15hp 2 stroke Problems

Won't hurt to check for thermostat condition, maybe not operating properly, place your hand at exhaust port while engine is on at idle speed, check to feel water cascading warm/cold, warm/cold intervals, if so, thermo is working correctly. If always constant cold or warm with no temp fluctuation change thermo.

Happy Boating

 

[Technologic80]

Re: Nissan 15hp 2 stroke Problems

Won't hurt to check for thermostar condition, maybe not operating properly, place your hand at exhaust port while engine is on at idle speed, check to feel water cascading warm/cold, warm/cold intervals, if so, thermo is workin correctly. If always constant cold or warm with no temp fluctuation change thermo.

Happy Boating

Thanks for the reply!

I went home on my lunch hour and ran the motor for a while, went for a little spin on the inflatable.

There is a cold/warm water mix coming out together at the exhaust port.

Today it didnt act up at all. The last time it acted up (Saturday), I put my hand at the water coming out of the exhaust port and it felt the same way it did today, lukewarm with some cold water mixed in.

Im seriously leaning towards the CDI or spark plug wires. My 1st theory is, after a while of cruising, moisture somehow gets its way under the cover and the wires start to arc. Again, just my theory and I could be way off. My 2nd theory is the CDI is suffering from a thermal failure and after a while of cruising when it gets warm, it shorts. Because it feels like its misfiring and I lose (what feels to be) about 25% off the top end speed.

Do either of those theories make sense or am I beating a dead horse here...LOL

 

[Sea Rider]

Re: Nissan 15hp 2 stroke Problems

On my horse you can feel the warm/hot/cold temp fluctuation well differenced, not mixed as you say. When thermo works ok at closed position will feel cold water exiting, when openning warm/hot water. Thermo conditions depends on how well you rinse engine after daily uses to avoid salt formation on thermo. Could be wire plugs caps, check interior terminal to see condition, replace caps if found rusty. Being a relative new engine could be anythig, including a failed thermo. If it's still under warranty take to dealer and stop guessing.

Happy Boating

 

[pvanv]

Re: Nissan 15hp 2 stroke Problems

You can try running with the cowl off to see if the cool air changes anything. If it does, you are 1 step closer to diagnosing the issue.

 

[Technologic80]

Re: Nissan 15hp 2 stroke Problems

You can try running with the cowl off to see if the cool air changes anything. If it does, you are 1 step closer to diagnosing the issue.

Thanks for the reply! I will do this when I get back home (5pm) and report back.

 

[Technologic80]

Re: Nissan 15hp 2 stroke Problems

On my horse you can feel the warm/hot/cold temp fluctuation well differenced, not mixed as you say. When thermo works ok at closed position will feel cold water exiting, when openning warm/hot water. Thermo conditions depends on how well you rinse engine after daily uses to avoid salt formation on thermo. Could be wire plugs caps, check interior terminal to see condition, replace caps if found rusty. Being a relative new engine could be anythig, including a failed thermo. If it's still under warranty take to dealer and stop guessing.

Happy Boating

Well, its a 1992 model year so its looooooong out of warranty! Also, the motor is only used in freshwater, on the Great Lakes.