Nissan 15 NSF15B2 long warmup times

[jgibbs2037]

This has me stumped. Even when new, this outboard would sometimes sputter a bit til FULLY warmed up. Suddenly this years its much more prevalent.

Typical use case...
65F water, Air between 55 and 70.
Start the engine (starts right up and idles great.)
2 minutes or so while loading (still great)
3 minutes or so while idling out to the bay (great)
OPen it up, runs great at WOT.
About a mile later, it starts sputttering/popping, and I have to drop to 1/2 or less throttle.
About another mile later, it gradually starts running fine and I open it back up.
restarts are fine unless it sits a few hours, then it can repeat.

I have sprayed out the carb (not fully cleaned/dipped yet).
replaced the thermostat
Sprayed out and tested the enrichment solenoid.
Fuel Filter
Plugs
Fresh gas.

Squeezing the bulb does not help.

I plan to flush out the cooling circuit and replace the water pump and remove the carb for a full dip/rebuild.

But its always did this a little even when new. This fall it seems worse. I am tempted to try running no T-stat as a test, then trying one thats a higher temp. I run in Michigan, its not that hot here..

Any ideas on other things to check? I am stumped. It seems like its temperature/T-stat related. Like when the stat opens, its cooling too much, or maybe the stat is opening late and its too hot for a while. But like I said, i replaced it anyhow.

Thanks in advance for ideas!

 

[Sea Rider]

Some issues :

How old is that motor, how many hours would you say the motor has been run ?
Been used in fresh or salt water ?
How about the fuel hose, is it fexible, bit hardened ? Is it possible to try other fuel line in excellent working order ?
How about warming the motor up way less say 1 minute, openening the throttle say 1/2 to 3/4 throttle for 1 minute and then full throttle.

Does that motor counts with a flushing port (nut located side of the powerhead )? If so, remove thermo, put the thermo cap back on and flush as long as you want. Did you know that 4 stoke motors tend to make more oil and the oil level rise higher than it should be, check oil level amount, should be no higher than the max line allowed. If so, remove old oil and fill with new.

Happy Boating

 

[pvanv]

After you clean the carb properly (especially the passage in the bottom of the bowl), a lot should be better.

 

[Sea Rider]

According to the OP : I have sprayed out the carb (not fully cleaned/dipped yet) If sprayed through the carb's throat won't clean nor cure a thing....What's strange is that's been doing so or at least partially since new.....

Happy Boating

 

[jgibbs2037]

Yes, its always been a tough "warmup" but used to never really happen in summer, just fall. Now its all summer, and is worse in fall. Seemed to happen all of a sudden.

I also ran a Seafoam treatment thru (no change).

Its a 2004 or 2005 engine, lots of hours (maybe 700?)

Its always been well maintained, and always good gas. But maybe a good carb cleaning will get it back to as it was, where it was just a slight nuisance.

I wonder if I should be playing with jets or anything, but I Michigan is pretty standard temp/altitude. Maybe 700 feet above sea level, and I use it from 32F up to 85F air temps.

But for now, the winterization will include a good flush/check of all coolant circuits, and a carb teardown/soak.

 

[pvanv]

Seafoam is just mineral spirits. Waste of time and money. Never seen it do anything. Just my opinion.
If it ever sat for a week or two with fuel in the carb, it needs a Proper cleaning for sure.
Standard jetting is fine for the Great Lakes.

 

[Sea Rider]

Slight loss of performance starts at 3K feet or 1000 meter of elevation, 700 feet is nothing. Perform a carb cleaning to immaculate condition and before the motor is put into operation again spray some CRC decarbonizer through the carb's throat after the motor has been sufficiently warmed up, follow can instructions. Seaform will be effective if used regularly, if no other cleaning product has been used since out of the box CRC is the way to go to smooth anything with pistons fully guaranteed...

Happy Boating

 

[jgibbs2037]

Resurrecting an old post...I've done everything suggested and all I could think of (and used a service manual.)
For some reason it seems like it's t stat related. The choke solenoid works, and based on testing is done moving within 30 secs or so. It's after a few minutes that it runs poor.
The colder the weather gets, the longer it takes to start running poorly. On cold mornings, I'm almost to my hunting spot anyhow. But then it takes longer to clear up (like the colder air and water is slowing the whole warmup curve).
As a test, after warming up I removed the Stat, and it ran poor the whole time.
Is there any thing that should be restricting water flow thru the stat? (Replacing Stat made no change)
I'm considering a 20hp upgrade anyhow, so am interested in trying a non-factory Stat with higher temp rating as a test, or maybe figuring out how to add a little restriction. I don't want to wreck it, but am open to some experiments that I would not do to a new engine.
Any ideas on finding a higher temp stat that fits?

Thanks for all the ideas last fall!

 

[pvanv]

Only stat is one that starts to open at 150F. If the stat is stuck partially open, warmup could take a very long time, especially in colder waters. Still likely a carb issue.

 

[jgibbs2037]

Only stat is one that starts to open at 150F. If the stat is stuck partially open, warmup could take a very long time, especially in colder waters. Still likely a carb issue.

I did replace the stat (factory is 140 for start to open) it didn't help. Visually it's not stuck open.
I was going to disassemble and dip the carb (again), but it's been soaked overnight and then sprayed out 3 times (chem-dip soak, then carb cleaner then airhose)
If you could tell me how to find that 150f stat I'd appreciate it. I know it's going off chasing ghosts, but it's always done this a bit, even when new, so I'd like to try.
BTW, that CRC engine spray really got the crud out. I've been recommending it ever since.

 

[km1125]

YOU are not going to notice a difference in the running of an engine at 120F or 180F. You might be able to measure it in fuel consumption, emissions, or power available, but you're not going to notice it by the "seat of your pants".

If the problem happens at WOT after a short bit, then it's a fuel or ignition problem. Either you have some restriction in the gas (plugged jet, fuel pump issue, etc), you're sucking air somewhere (although if you pumped the priming bulb while this was happening it should have impacted the symptom), or you have some kind of ignition issue. The earlier comment about the oil overfilled might be a clue. I'm not sure on that motor if you get the same "foaming" problem you get on the smaller motors (which will lead to a loss in oil pressure and potentially triggering the 'low oil pressure' switch), but it's a possibility. There could be other ignition issues. Have you connected a tach to the system? If you're using one that's triggered by the spark lines, you'd see erratic readings if the ignition system is acting up when your symptoms appear.

 

[jgibbs2037]

YOU are not going to notice a difference in the running of an engine at 120F or 180F. You might be able to measure it in fuel consumption, emissions, or power available, but you're not going to notice it by the "seat of your pants".

If the problem happens at WOT after a short bit, then it's a fuel or ignition problem. Either you have some restriction in the gas (plugged jet, fuel pump issue, etc), you're sucking air somewhere (although if you pumped the priming bulb while this was happening it should have impacted the symptom), or you have some kind of ignition issue. The earlier comment about the oil overfilled might be a clue. I'm not sure on that motor if you get the same "foaming" problem you get on the smaller motors (which will lead to a loss in oil pressure and potentially triggering the 'low oil pressure' switch), but it's a possibility. There could be other ignition issues. Have you connected a tach to the system? If you're using one that's triggered by the spark lines, you'd see erratic readings if the ignition system is acting up when your symptoms appear.

I know I am really reaching on this one...Normally I'd also say that a 10F higher stat wont make a difference.
My theory is that maybe when the stat opens, the cold water is cooling the engine down enough that it needs more choke (but the choke is automatic, so its already fully open).
Then as I keep going, the engine gradually warms up and starts running good again.
So I was just wondering if delaying that stat opening would get me further into the warmup, and make it run better.
The low oil light does not come on when its running poor in this "mid warm up" stage.
I could be totally wrong as well. But I've gone thru pretty much everything, I did add a tach (but only tried it on one plug) but the stumper is that it runs great, then bad, then great again. Once up and running (fully warmed up), its a champ.

 

[pvanv]

Yeah, the 60C stat does begin opening around 140F. That's normal. I personally would revisit the carb.

 

[Sea Rider]

Is it possible to check if the automatic choke's internal parts are working closing/opening properly, could be jamming taking to much time for the carb to work properly ? See if can slight lube those mechanical parts ?

Happy Boating​

 

[pvanv]

Is it possible to check if the automatic choke's internal parts are working closing/opening properly, could be jamming taking to much time for the carb to work properly ? See if can slight lube those mechanical parts ?

Happy Boating​

Nah. It's a heater inside a wax capsule that extends a needle to lean out the carb. It's called ABS or auto by starter. They never fail.

 

[jgibbs2037]

I did remove and check the ABS (choke). I hooked it up to a 9v and after about 45 sec it was out position.