Exhaust High Temperature alarm

hpg4815

Cadet
Joined
Jul 23, 2014
Messages
10
Hi All,

Last Saturday I was taking my 2012 Chaparral Xtreme out and I put the boat in the water and started it up. I usually let it warm up a bit before leaving. The dock slip sits in a no wake zone, so when I pulled out I was just at idle speed. About 150 yards from the dock, and still moving at idle speed the entire time, an alarm went off. It took me back, but with in less than a minute we discovered it was a alarm for high temperature. I shut it off. The temp cooling gauge stating 213 deg. After we shut if off, I opened the engine lid, and immediately saw that I left the cap off that hose you use to flush the engine. I clearly forgot to put it back after last weekends engine flush. I'm really beating myself up over this mistake.

I of course put the cap back, and let the engine cool off. I waited until it got down to 173 deg and started back up to see if the raw water pump will now be able to do its job and cool the engine. The temp started rising, and when it got to 206 deg, i shut it off again. I then took the sink sprayer and sprayed some fresh water down that same engine flush hose. I then waited until it got down to 139 degs. When it did I started it up and go on a plane, the temp got up to mid 170's and then went down to its normal operating temp of 150's. I was very happy and thought everything was good. While driving from that point on, I never really went over 30 MPH and was just cruising. I ended up having to go through another no wake zone and everything still seemed fine. It wasn't until I go on a plane in the bay and was moving at speeds around mid to upper 30's MPH. Another alarm went off, I say another because although the alarm sounded the same the technician's display was saying something different, something about the exhaust temperature? The water temp or engine temperature which I was monitoring the whole time since the incident was still at a good temperature. The manual stated that when these alarms when off, that the RPMs of the motor will automatically be reduced, which they did, so the provisions put in place did work. I was able to drive back to the dock at around 25-29 MPH and less than 3000 rpm without the alarm alerting.

My question(s) are, and the main one is. What serious problems did I cause myself after leaving this cap off? Am I looking at internal engine damage? Do the audible alarms need some sort of resetting after being set off? I would like to mention that earlier this year I had to get a new raw sea water pump because the other was leaking. I'm assuming it came with a new impeller too. If that is the case, could I have messed up that impeller? Even if it wasn't replaced the previous service I had done didn't mention anything about replacing it. Could it have messed up the impeller in some manner? I only have 100 hours on this boat. I checked the oil level and that was fine, but I read on other post about the risers sucking in water when overheating? I don't recall seeing any water on the dip stick, and like I said earlier the boat ran fine up until I got it above 3k RPM and pushing 40 MPH. I took it back to storage and flushed the engine like I normally do and put it up. I was planing on taking it out again to see if the problem went away. I realize that sounds silly, but would it be possible there was a air pocket stuck somewhere? Or that everything was just so heated up at the time that a thermostat was stuck? Speaking of stuck, in regards to the starter, there was a couple times I started the engine so that it would pull cooler water in the engine (because the water that was in there was really hot), and it appeared the starter stuck trying to start the engine. I think, it was a sound that continued after the motor started. When I waited until it cooled to the 139 deg the starter functioned at normal. My assumption was that everything was overly hot, resulting in the starter to stick open.

I have that gut wrenching feeling in my stomach that I really blew it here, but at least no one died.

Thanks
 

hpg4815

Cadet
Joined
Jul 23, 2014
Messages
10
Thanks for that. can you elaborate on why that would be? What actually caused the impeller to go out?
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,454
Maybe I should ask a question first.

Is your flush fitting before the impeller? Basically, do you need to have the engine running to use the flusher? If the answer is yes, then there was air entering the impeller and it lost its prime allowing it to run dry.
 

hpg4815

Cadet
Joined
Jul 23, 2014
Messages
10
I would have to confirm, but I don't think that is the case. If I hook up the hose to the flush fitting water will immediately start pouring out of the exhaust and water intakes from the outside lower unit. Then i start the boat. It is not like a wave runner I had where I was instructed not to leave the hose on and pumping water into the flush fitting without having the engine turned on. I see! Maybe your right though. Maybe despite the fact the boat was in the water, and that the flush fitting is after the impeller it still got hot enough to dry out and cause enough damages to it where it doesn't cool properly during high loads. (3500 plus RPM/ max speed). What do you think? I'm really contemplating tying to inspect the impeller. You think it would be OK if I run the boat first to see if it was just a air pocket or something was causing the water not too exit the exhaust fast enough during that day? Do you think its possible these alarms need to be reset?
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,454
Ok..good thing I asked. If it's on the back side of the impeller, then you wouldn't suck air into the impeller by leaving the cap off. You probably did have a lot of water enter your engine compartment right?
 

muc

"Retired" Association of Marine Technicians...
Joined
Jul 7, 2004
Messages
2,064
You need to replace your impeller.
Your symptoms point to a worn impeller. Do not run the engine until you inspect --- read replace --- your impeller. If any pieces are missing from your present impeller you should find them, disassemble hoses and thermostat housing and find them. You do not have an "air pocket".
 

muc

"Retired" Association of Marine Technicians...
Joined
Jul 7, 2004
Messages
2,064
You don't need to reset your computer, it did that when you turned the key to the off position.
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,454
I just read the engine flushing procedure in a 2012 owners manual. The engine needs to be running to flush the engine so it IS on the input side of the impeller. The water you see when you turn the hose on is just water going back out the drive and it isn't actually flowing through your engine.

You haven't been flushing your engine if you haven't had it running.

Read your owners manual in the section "After Engine Shutdown, Engine Flush"

VolvoFlush.JPG
 
Last edited:

hpg4815

Cadet
Joined
Jul 23, 2014
Messages
10
@bruce58 not a lot of water in the engine compartment. When I first had the boat serviced, the guy warned me about leaving that cap off, and stated it would suck in air then heat the engine (yes. I was warned, just screwed up and forgot). So I can see why water was not coming out of the flush fitting. Some did come out when I filled it up with water, and when I periodically open the cap while we were just waiting for the engine to cool down to see how hot the water was at the time.

@Muc Ok, your right, I will either look at the impeller myself or take it in to the shop.

Do either of you think I caused any major damage based on my story? What about the horror stories of sucking water in through the risers to the engine? Something about water locking? Do gaskets and seals shrink at 213 degs? if you know if course.
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,454
213 is not that hot if that's all it got to. Automotive engines can run hotter than that with a pressurized anti freeze cooling system.

The things that can have a problem are the rubber hoses after the riser since they are cooled by the water coming out the exhaust. Inspect them to see how they look. If it got hot enough, they would actually have a hole in them.

No problem with the water getting into the risers. Not only is that not a problem but your pump wasn't pumping any water up there!!! :)
 
Last edited:

hpg4815

Cadet
Joined
Jul 23, 2014
Messages
10
@bruce58, I see what your saying. I was thinking of that example in regarding to the wave runner I used (thinking the engine was required to be on in general). Yes, I do need to turn on the engine to actually initiate a flush. I did read somewhere that if the hose has too much force that it could cause some damage to a particular seal in the raw sea water pump, so I never really turned it on full blast. So it sounds like after this discussion that I did cause damage to my impeller.
 

skydiveD30571

Lieutenant Junior Grade
Joined
Feb 13, 2012
Messages
1,042
After you check the impeller, visually check both exhaust elbows and the rubber bellows that connect the exhaust elbows to the y-pipe (same thing Bruce is talking about). The exhaust temp sensors are on the aft side of the exhaust risers and can get hot enough to melt and start intermittently sounding the alarm. Ask me how I know. Hint: I did the same thing you did....left the flush cap off.
 

hpg4815

Cadet
Joined
Jul 23, 2014
Messages
10
Thanks Skydive.. I'm going down this weekend to address the boat. I'm mechanically inclined so I'm thinking about changing the impeller and conducting the inspection on my own. DO you think its better I just tell the mechanic what I did and have them do the inspection. My concern is I don't inspect everything properly. I don't know what the exhaust elbows and the rubber bellows are, or if I'm looking at the right thing. I'm assuming the risers are the big arching exhaust manifolds on each side of the motor? Since you did the same thing (left flush cap off) did you do any serious damage? Do you still have the boat and is it running fine now? I realize it most likely not apples-to-apples, but it gives me faith.
 
Last edited:

skydiveD30571

Lieutenant Junior Grade
Joined
Feb 13, 2012
Messages
1,042
What engine are we talking about here?

Take a look at the linked diagram. It is for a 5.0GL but the exhaust parts are pretty standard:

PN #8 = manifold
#1 = riser
#14 = elbow
#6 & # 16 = rubber exhaust boots
#4 = temp sensor

Check to make sure the rubber boots are not cracked and leaking water. They can melt pretty easily during an exhaust overheat. The wire on the temp sensor just pops off and then the sensor can be removed with a socket.

I did not cause any serious damage to mine. I caught it pretty quick like you did. The first thing after an overheat is to ALWAYS replace the impeller. Just because it looks OK does not necessarily mean it is. Being such an important part, it's worth it to just change it out. When you remove the old one, make sure no rubber pieces are missing. If there are, you'll have to go searching for them (most likely in the thermostat housing). After impeller replacement, run the engine and check for leaks and proper running temp. The exhaust elbows should never get too hot to touch. If they stay cool but the alarm still sounds intermittently, the sensor is most likely bad now but it is a cheap replacement. Pulling the wire off the sensor will quiet the alarm. If all is good, shut her down and check the oil for signs of water.

There's no way to tell from here, but I think you'll be ok. The horror stories you read about gasket failure etc usually involve more extreme overheats for longer periods of time.
 

vinnie1234

Petty Officer 2nd Class
Joined
Jul 7, 2014
Messages
161
213 is not that hot if that's all it got to. Automotive engines can run hotter than that with a pressurized anti freeze cooling system.

It is worth noting that; when an engine loses coolant, the temperature guage (coolant temperature sensor) may not be reading block or coolant temperature accurately. If the sensor is placed near the top of the engine, once the coolant drops below that level, then it is only reading the temperature of the air in the coolant passage and it therefore offers a false temperature reading on the low side. You can't always rely on engine temperature readings when loss of coolant is involved.

Don't think it really matters here, but I thought I would mention that little tidbit if for nothing other than future reference. It has come in handy for me a few times being aware of this fact.

If (in this case) problems persist after the impeller change, this may help you to save further damage. In the event that the overheat caused a gasket failure or crack in the head, combustion pressure can drive gases into the cooling system and displace the water, causing an overheat. Depending where the sensor is located, you could make matters worse because you would be unaware of this otherwise. If you had a leaky headgasket as a result of the overheat, a more severe overheat could cause a warp in the head or cracks.

Once this problem is all fixed up, I would be checking the coolant hoses regularly during operation to ensure that they are full of water.

Good luck .
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,454
It is worth noting that; when an engine loses coolant, the temperature guage (coolant temperature sensor) may not be reading block or coolant temperature accurately.
Yep, that's true.

What actually saved him is the exhaust temp sensor likely.
 
Last edited:

hpg4815

Cadet
Joined
Jul 23, 2014
Messages
10
meaning that my engine actually got hotter than it was reading? ...*stomach turning*....
 

vinnie1234

Petty Officer 2nd Class
Joined
Jul 7, 2014
Messages
161
Not necessarily. It's just something to be mindful of after the repair to the cooling system. Not trying to freak you out.
 
Top