Cutting out and stalling

[BOWTECH.JUSTICE]

2002 50hp Nissan NSD50A TLDI. Runs great at first then after a while, mostly at low idle it will start cutting out and eventually stall. Also at high RPMs it will start missing at the higher temp. It seems to be a fuel issue. New fuel line and primer bulb last year. Bulb is secured vertical for fuel flow. New thermostat, plugs. Checked all fuel lines and filters. Also check the fault codes and one time it will say overheat and next time it will be low charge on battery. I'm at a loss at this point so waiting to hear what the experts have to say. Thanks in advance.

 

[pvanv]

I would verify the temperature is OK using an IR thermometer. Also verify battery is in great shape. You need a bigger battery than you may think. Then reset fault codes and reset TPS initial setting.

 

[BOWTECH.JUSTICE]

I would verify the temperature is OK using an IR thermometer. Also verify battery is in great shape. You need a bigger battery than you may think. Then reset fault codes and reset TPS initial setting.

Thanks. I will check these. Maybe the battery is failing. What is the adequate temp? If I remember right, doesn't the Nissan's tend to run hotter than others? Also, could the compressor drive belt have anything to do with this?

 

[MattFL]

Not to go off on too much of a tangent, but do you guys who work on boat motors find yourselves having to set the TPS often? If so, would this tool be helpful:

 

[BOWTECH.JUSTICE]

Manual says TPS should not be adjusted but can be replaced. Temp is within spec except when running at idle. There never has been much water flowing through the tell tale at low RPMs. Water pump is also new. I did get a reading in the mid 170s at low RPMs but as soon as I reved it up a little, the temp dropped back to normal. Also checked compressor drive belt and it seems to be ok

 

[MattFL]

Look in the manual where it explains replacing the TPS. There are 2 ways they work. The first is the TPS is manually adjustable and they'll have a little procedure for adjusting it. In this case you can check to be sure the TPS is set properly. This is where the meter I linked above would help. The second way is the TPS itself is not adjustable, and after replacing it they'll have you do some procedure where the motors ECU will "learn" the idle and full throttle positions of the TPS.

In either case, you can test to make sure the TPS is not going bad. Use a meter like the one above, or a multi-meter (the manual will have instructions) and slowly open and close the throttle. Since your problem is at or near idle, concentrate on that area. Watch the reading and make sure it changes smoothly and doesn't have any sudden jumps or drops.

All of that said; if the motor is hotter than spec when the problem begins, is it possible the motor is going into a limp mode? It's not uncommon for some motors to go into a reduced power mode when they get too hot, in an effort to prevent catastrophic failure. This mode can appear like the motor is missing, similar to how it sounds when it hits the rev limiter, but at a much lower rpm.

 

[BOWTECH.JUSTICE]

It could possibly be shutting down because of temp but then again, sometimes it seems like a fuel issue. This thing never has had much pressure from the tell tale at idle. Actually water only comes out sporadically.
Also it occasionally sputters at WOT. Not often but it does do it. It's kinda like a miss for just a second then back to running fine. I just need to keep testing things and narrow down the search.

 

[MattFL]

Some motors dribble water and others spray with a lot of pressure, maybe someone here can say what's normal for that specific motor. Also if you're wide open and it stutters, it's going to be difficult to say if that's a real problem or if you're hitting the rev limiter, unless you can connect a tachometer. You can get a combo hour meter and tachometer on Amazon for around $20, and if you get the right one it will remember the max RPM's that the motor ran. You can use that to figure out if you're hitting the rev limiter.

 

[pvanv]

Also check fuel and air pressures at the rail.

 

[BOWTECH.JUSTICE]

Also check fuel and air pressures at the rail.

That's a question I have and I'll look for it in the manual. What's required temp and what if it's low?

 

[BOWTECH.JUSTICE]

TPS readings are within spec

 

[Sea Rider]

That's a 19 year oldie, was always run in fresh or salt water which will determine how salted or dirty are all the water passages inside the powerhead. The issue is don't expect to read the same temp say on the cylinder or exhaust chamber measured when out of the box compared to your motor which has been in use for that long time...

Happy Boating​

 

[BOWTECH.JUSTICE]

That's a 19 year oldie, was always run in fresh or salt water which will determine how salted or dirty are all the water passages inside the powerhead. The issue is don't expect to read the same temp say on the cylinder or exhaust chamber measured when out of the box compared to your motor which has been in use for that long time...

Happy Boating​

Fresh water. Yeah, just trying to see if it's a simple fix to keep it alive. Overall it's still a good running motor. Something I failed to mention is that this is a rental pontoon. It's rented to regular cottage renters every year but trying to explain to all of them the scenario is difficult at times. Everyone nowadays likes turnkey operations so I know eventually this motor will need replaced but I'm just trying to make it last as long as I can. I think these issues happen when the motor is run constant for a considerable amount of time so I'm just going to have to make it known to not do that. I myself can take that boat out and not have any issues but that's not always the case with my renters.

 

[pvanv]

Temps should be about 150F. Did you reset TPS initial setting per the FSM? What are the fuel and air pressures?

 

[BOWTECH.JUSTICE]

Temps should be about 150F. Did you reset TPS initial setting per the FSM? What are the fuel and air pressures?

Didn't check the air/fuel yet. Will have to wait till the weekend.
Did not reset the TPS because the readings were within spec but I'll read into that.
The temps are always good until it sits in idle. When in idle, not much water pees out and the temps will go up to as high as mid 180's.
Thanks again

 

[MattFL]

Just throwing ideas against the wall; when you replaced the water pump, did it get a whole new pump or just the impeller? Also did you double check the seal between the pump and the tube that takes water up to the motor? It sounds as if the motor might not be getting enough water flow at idle (and maybe full throttle) so I'm trying to think of things that might decrease pump efficiency.

 

[BOWTECH.JUSTICE]

Just throwing ideas against the wall; when you replaced the water pump, did it get a whole new pump or just the impeller? Also did you double check the seal between the pump and the tube that takes water up to the motor? It sounds as if the motor might not be getting enough water flow at idle (and maybe full throttle) so I'm trying to think of things that might decrease pump efficiency.

Just throwing ideas against the wall; when you replaced the water pump, did it get a whole new pump or just the impeller? Also did you double check the seal between the pump and the tube that takes water up to the motor? It sounds as if the motor might not be getting enough water flow at idle (and maybe full throttle) so I'm trying to think of things that might decrease pump efficiency.

2 years ago I rebuilt the lower unit so all the seals were changed. Plus, the water flow now is the same as before the rebuild.

 

[BOWTECH.JUSTICE]

Also check fuel and air pressures at the rail.

Been a few days but I finally got to the boat again. Just checked rail. Air is 80 psi/ fuel is 90 psi. Both within spec.

 

[BOWTECH.JUSTICE]

I changed low pressure fuel pump. I took it out and after a while of just idling around, it stalled. No sputter as in running out of fuel. More like the key was turned off. Primer bulb was still tight. I cranked it a couple times and it started right up.

 

[pvanv]

What led you to replace the low pressure pump? When it stalled, were the plugs wet or dry? Any issues since?