2020 PS overheating warning

[lefty]

I think this may be a one off, spent a few hours at 10mph on a warm ish day wake foiling and noticed the warning the next day. 
engine did not shut down 

I cleared the error then did the usual and obvious things, cleaned the strainer(minor debris), checked intake through hull, looked for hose cracks leaks, checked impeller , see attached. Is this what they normally look like? Rubber felt supple as it should, impeller is 4 months 30hrs old. 
will watch Temp gauge closely for the next bit.
Skied the boat and was fine. 

Anyone else have this happen ?  Have heard these engines run warm but it lives in Ontario not Texas

thanks for any  insight

[jpwhit]

You have to pull the impeller out to tell if there are any issues. Sometimes there is chunk missing out of the middle of one or more of the vanes. Also check to make sure the rubber isn't spinning on the hub. Sometime the bond between the brass hub and rubber part of the impeller breaks free. When that happens the impeller work somewhat but will slip enough to allow overheating in certain conditions. 

It's likely the conditions you were running the boat did make the issue show up, but it's not normal and it shouldn't have happened. I'd say something is definitely wrong, but not something that's so wrong it'll show up in other scenarios. But it would be best to find and fix the problem now, before it gets worse.

A likely culprit is a small air leak somewhere on the suctions side of the raw water system. Something letting air in between where the water enters the hull fitting and the intake side of the raw water pump. Most MasterCrafts have clear fittings on the connections to the strainer. Look at those carefully when it's operating in the kind of conditions where it overheated. You shouldn't see any consistent pattern of bubbles in either of the two clear elbows on the raw water strainer. If you do, then that's a clear indication of air leaking into the system, at least up until the point of the strainer. 

[ColeGiacopuzzi]

@lefty That error can also be from the check valve at the back of the motor, an air bubble gets caught and water can't flow and the motor starts to creep up in temperature, but usually under power the bubble gets cleared and you can watch the temp fall instantly. It was a known issue on the 6.0L 2020 Prostars. The plastic check valve from the factory weren't very good and you can buy an aftermarket brass one. Might be worth checking at least and making sure the clamps are tight. Hope this helps. 

[Cnewbert]

What @jpwhit said "A likely culprit is a small air leak somewhere on the suctions side of the raw water system. Something letting air in between where the water enters the hull fitting and the intake side of the raw water pump" is exactly right.  We have the same boat and it developed an overheating problem out of the blue last fall. Turns out the sealant for the clear elbow at the inlet for the raw water strainer was faulty, admitting air into the water flow.  It never leaked a drop of water, but air was getting sucked in causing the overheating.  Quick and easy fix by resealing it.  Also, as @ColeGiacopuzzi said, the PRV can also be the source.  The Ilmor manual says they're meant to be replaced every 100 hours.  Replace it with a brass one like he said.  Another quick fix if that is the problem. Thermostats can go bad, rarely I'm told, so it's probably not the source of your overheating.

But there's one other possible culprit: Curiously we developed a second overheating problem 8 months after the issue with the bad sealant.  This one defied diagnosis as we did all the usual checks and replacements.  Nothing worked.  It turned out we had a plugged cross-over tube.  This is somewhat of an obscure part, and even when I had the new one to try, I couldn't find the existing one in order to replace it.  It's hard to even see at the front of the motor, as it's more or less hidden under the alternator on the left side of the motor, plus everything is painted blue making it even harder to pick out.   Once I found it, the replacement was relatively easy, except the alternator has to be removed and it's like a Chinese puzzle getting it completely out to expose the left end of the cross-over tube.  (The right end is exposed and easy to access once you know what you're looking for). Anyhow, this tube was plugged at one end.  I put the new one in and everything was back to normal.  So if nothing else works, consider the cross-over tube as a last resort.  You can take out the one you have, plug one end with your finger and blow through the top hose connection. Air should come out the other end.  Then reverse the process to see if either side is plugged.  

[lefty]

Thank you for the replies. I did look at the check valve, it has new looking Teflon tape and is brass so I expect it was changed recently. I did also look at the clear plastic elbow during idle but I will do that again and look more closely. Also will pull the impeller just in case. Failing any positive diagnosis I will try the cross over tube issue as @Cnewbert suggested. If I find the culprit I will post it 

[Cnewbert]

Because the cross over tube is rarely —  if ever — mentioned in overheating trouble shooting discussions for the Ilmor 6.0 in late model Prostars, and because it’s hard to even locate, I’ve included a photo of the plugged one I replaced, which instantly fixed my overheating problem after everything else in the system was either inspected or replaced. 
 

A descending rubber hose with a hose clamp on the right front of the motor connects to the vertical portion of the tube. That’s the easiest part to locate.  The rest of the tube is pretty much obscured from sight and the left side is under the alternator and can only be seen from certain angles. Once the alternator is removed and the rubber hose detached, the tube is very easy to replace with a single bolt on the left and right. 
 

I still don’t have a clear understanding of what this tube does or how such a small diameter tube when plugged could have such a dramatic effect on the engine cooling, but it does.  I hope this might help someone or save them a trip to the dealer. 
 

 

[BraceMaker]

It's usually called the steam pipe. With out it the heads can basically boil off some fluid and then that vapor expands and blows the antifreeze out 

[lefty]

I haven’t been able to get back into the boat for a bit but am curious @Cnewbert can the tube be unplugged instead of replaced?  Could you tell what plugged it?

[paul]

I unplugged mine with some vinegar

[Cnewbert]

@lefty I’m fairly certain it could be. I just put in a new one as it was a warranty replacement. I’ve saved the old one and will try and unplug it one of these days.l to have as a spare. Until then I have no way of knowing what plugged it, but the I.D. is quite small, so it wouldn’t take much.

 

[lefty]

Had a few runs in the boat last few days. This morning the engine icon was back. The analog gauge did not ever show over 170* in the last 3 uses since the initial warning. Am now thinking that I was not successful in clearing the error completely from the system. Also idled the boat  to look for air bubbles and saw none in the elbow or screening canister. Located the crossover tube in case that is the culprit.
So I guess to begin, am I able to clear the error message completely and if so how do I accomplish this?