Overheat cause?

[UnfixedPyle]

I was out yesterday with some friends and about an hour into wake surfing got a port engine overheat. I was the one surfing and a friend was driving the boat. It happened right when he throttled back after I fell. He had it shut down by the time he got back to me and thanks to this forum I was sable to figure out how to reset that pesky check engine light that didn't want to go away. Anyway, I didn't really find a smoking gun for what caused it. It's possible the cooling flow was a bit weak when I started it back up but was fixed rapidly, oil level was fine and clean out ports were all good. Engines ran fine after letting it cool and we stopped surfing. I'm kind of hoping to find a definitive cause so I can try and avoid it in the future. Is there anything else I should check?

Surf setup included full internals and transom ballast on the port side. Engines were running between 6000 and 7000 rpm which I have done many times. It might not have had anything to do with surfing but including the info just in case it matters.

 

[Cobra Jet Steering LLC]

Possible cause is increased back pressure on your exhaust system with the back of the boat sitting so low there are posts on this like why the low side engine won't start after they let it sit and having to get the boat going on the high side engine first, and then starting it when the boat is moving just a possibility. So do a search

 

[UnfixedPyle]

Bumping this back up to the top. I'm out on the water right now and got the overheat within 10 min of surfing again. This time I wasn't even using all of the ballast. I ran all last summer no problem. I can't find any obstructions, cooling water is flowing the same on both engines. Oil level is fine (if anything it might be a bit on the high side). Any ideas what can be causing this?

 

[UnfixedPyle]

I finally searched the right thing and found some overheat posts that are similar to mine.... 2021 SX190 - overheat warning but reality seems unlikely - suggestions? | Page 2 | JetBoaters.net - The World's Largest Jet Boat Forum! . I also talked with a tech at the dealer who said if the water flows its probably a sensor or electronic issue which matches these other threads.

I can now make it "overheat" any time I'm not running on plane or idling, basically any time the nose of the boat is up no matter what the RPM is and the water is flowing cool. Dealer can't get me in to check it and hopefully fix it under warranty until June 7th and I have a bunch of family coming into town this week through next weekend with plans for boating. I'll have the IR temp gun ready to check it if it goes off again.

 

[Cambo]

Do you have any more cavitation than normal?
Any problems getting to the 11mph range while surfing ?

 

[UnfixedPyle]

Do you have any more cavitation than normal?
Any problems getting to the 11mph range while surfing ?

No, everything appears normal and drives just fine.

 

[Babin Farms]

Swap sensors with the other engine to see if the problem follows the sensor or not.

 

[UnfixedPyle]

Swap sensors with the other engine to see if the problem follows the sensor or not.

Question is which one? From what I see in the diagram there are three.

I kind of suspect the thermosensor in the exhaust because it appears that the wire was bent/kinked so I wonder about it's integrity. So I guess I could start there. The other 2 are much harder to get to.

 

[Babin Farms]

Question is which one? From what I see in the diagram there are three.

I kind of suspect the thermosensor in the exhaust because it appears that the wire was bent/kinked so I wonder about it's integrity. So I guess I could start there. The other 2 are much harder to get to.

One at a time and test.

 

[Beachbummer]

Do check your pump!!! water pressure is affected greatly by sealant dislodging or the smallest stick, just unluckly stuck in the wrong place.

 

[UnfixedPyle]

I have double checked everything. I can't see any damage or obstruction in the pump. I pulled the thermostat and tested it, opened right up at 140 and was full open by 155ish +- thermometer error. Double check flow through the engine without the thermostat installed and without the thermostat, flow is good and solid. If anything its actually better flow than the right engine, but either way full pressure coming out of the water discharge port by the pump. If there was a restriction, there isn't now. I'm headed out tomorrow with a bunch of family that is in town. I've got an infrared temp gun so I can check if/when the light comes on. Hopefully it doesn't make our day too awful. I might try swapping sensors between engine tomorrow if the temp warning pops up again. Depends on what we are doing at the time I guess. I might have this solved before I ever get it in to the dealer to see if the codes point out the correct sensor.

I do have one question, does anyone know what temperature the warning should come on at as measured with a temp gun?

 

[UnfixedPyle]

***UPDATE***

Just got the boat back from the dealer. They said they have seen this on one other boat. They updated the software on the ECU and ran full diagnostics and couldn't find anything wrong with the sensors. Supposedly the ECU update is supposed to fix it. I won't know until I can take it out again which won't be until the 18th or 19th. I am a bit skeptical, but they said the other boat that came in with similar problem hasn't been back since the software update.

 

[knoxboatin]

Well, I mentioned this in other threads you may have seen… If you have dual batteries with a switch that separates them, only Drive the boat using the battery that is also connected out of band to the bilge pump. Use the other battery as “house” if you like to run a radio and stuff when anchored. I have no explanation why other than me pissed many times with a bogus overheat alert and a process of elimination, no electrical science to share. You are better off with a single battery than electrical gremlins spoiling good boat times.

 

[UnfixedPyle]

Finally got to take it out today, and surprise, surprise the software update didn't fix it. Happened super quick this time, within about 2 minutes after getting up on plane.
One new thing this time, it managed to set the overheat alarm with none of the temp sensors plugged in. I also noted an ODB-M code of 521017. Anyone know what that is?

I charged both batteries tonight and we are going out again tomorrow, will see what happens I guess. Of note with the batteries, I am not able to run the boat on only one battery, it makes me turn both on before the connext screen will turn on.

 

[FSH 210 Sport]

Have you pulled the filter screen on the associated jet pump to make sure no debris is in there? I see you checked water flow on the engines with and without the thermostat..I assume that was on the hose?
Did you check the ground connections on the engines and or all electrical connections on the batteries and the battery switches?
Did you ever try swapping sensors?

 

[UnfixedPyle]

I have done all of things except swap sensors... Except I swapped the inlet temp sensor this morning because the one I pulled out on the left had some oil (not engine) on it. I brought tools out with me today. Only one I can switch on the water is the exhaust one but I might try it.

 

[tdonoughue]

What did you find with the IR gun? Is the engine actually overheating? You should be able to tell 'normal' for a location by the other engine that is not throwing an alert.

My money is still on a sensor. But on a 2022... shouldn't have sensors going out so soon. But then again, stranger things have happened.

 

[UnfixedPyle]

What did you find with the IR gun? Is the engine actually overheating? You should be able to tell 'normal' for a location by the other engine that is not throwing an alert.

My money is still on a sensor. But on a 2022... shouldn't have sensors going out so soon. But then again, stranger things have happened.

Yeah, I temp everything with an IR gun, the "overheat" engine is always 5-20 degrees cooler than the other one in every spot I compare.

I swapped the exhaust temp sensor today and nothing migrated, I'll swap the sensor on the rear of the engine tomorrow but unfortunately I am starting a new job this week and will be in training for ~50 days and probably won't be able to take it out.

I'm still confused how it can pop an overheat with the three thermo sensors unplugged?!?? Maybe the ECU is just bad, IDK. I'm trying to coordinate an on water evaluation with the dealer but the new job is making that difficult.

 

[Beachbummer]

I recently had to troubleshoot a weird overheat false alarm on an MR-1. Some sensors are analog and others are just a switch. The computer connection here would help greatly so you know which sensor the computer says it's reporting overheat.

I purchased a 250k potentiometer and used it to set it to the expected sensor value to test without the suspect sensor. (In my case exhaust, reads at 150k at 300C and 1K at 500C)

If at idle the pissers are showing water and the engine does not overheat, but it does overheat at higher temp, you may have a water flow problem. But you would notice it on water temp and exhaust manifold area with your temp gun.

Best of luck on your troubleshooting.

 

[tdonoughue]

Yeah, computers are magical things... if you know how they are programmed and if they are programmed correctly. If the sensors are the binary type (and I don't think that ours are) or analog, then an unplugged one is the same as either an overheat or cold condition. It is entirely possible that the computer is programmed to not register an overheat for the first bit after startup (because the sensor may generate noise on startup, which should be ignored, and certainly in the first 15 seconds or whatever there would not be an overheat). So, whenever the computer was programmed to finally look at the sensors, the open circuit (infinite resistance) could show up at that point as an overheat.

Note, this is supposition. I don't know exactly how they program the ECU on our boats. But it is certainly possible (obviously) to get an overheat with an unplugged sensor. That part does not surprise me.