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  1. #1

    Overheating Gremlin

    Hi everyone,

    I own a 2010 RXT-X 260 and back in February 2013 my ski filled with salt water whilst riding offshore. The sinking of the ski in salt water was caused by the ski's mechanic forgetting to tighten a hose clamp. The ski was under water for about an hour until it was towed to the nearest beach ramp where I was able to drain the salt water out of the hull. Ever since the sinking in salt water the ski has developed the following problem.

    After launching the ski I warm up the engine for a few minutes at idle speed to 84-89 degrees Celsius (engine temp can be displayed on dashboard). Now, when the ski is ridden at continuous Wide Open Throttle (WOT) on flat lake/river water the displayed temp gradually rises above 89 degrees (normal operating temp) and after three to four minutes at WOT this reading reaches 110 degrees at which point the overheating warning light and alarm/buzzer come on. At 111 degrees the ski goes into Limp Home mode. When displayed temp falls below 100 degrees the warning light and alarm/buzzer turn off. The speed at which the ski is ridden determines how much the displayed temp rises. For example, cruising at 75km/h causes the displayed temp to only rise to 95 degrees. Riding the ski faster than this speed results in a higher temp being displayed.

    Mechanic has confirmed, by installing an aftermarket engine temperature monitor/gauge and by pointing an infrared heat gun at engine after alarm/buzzer sounds, that engine is not actually overheating. For some reason, only the displayed temp on the dashboard is indicating temperature is high. Ski is not leaking oil or coolant, nor is there any cross-contamination of these fluids. Ski is not burning oil. Everything else on ski works perfectly and engine runs/sounds smooth. Acceleration, max RPM and top speed are all normal. There are no blockages in any water, coolant, air or oil hoses or the jet pump. Accepting responsibility for the loose hose clamp, mechanic has replaced/rebuilt engine. During the past 19 months the parts listed below have either been checked, replaced or temporarily swapped out by the mechanic to try and solve this issue:

    Wiring loom (main)
    Wiring loom (steering)
    Wiring loom (engine)
    Engine ECM
    Exhaust temp sensor
    Engine temp sensor
    Exhaust manifold
    Exhaust resonator
    Exhaust muffler
    IBR motor/actuator
    Ride plate (flow tested)
    Head gasket
    Oil cooler
    Coolant cap
    Intercooler
    Coolant
    Cluster (aka dashboard)
    Thermostat
    Water pump/impeller

    I believe the mechanic is close to running out of ideas and would really like to hear from anyone who may know what is causing this issue and how it may be fixed.

    Thanks in advance.


  2. #2
    k-dub's Avatar
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    I'm having a similar issue. I can run the boat all day but if I run hard for a time it throws the engine over temp alarm.

    I have read that this is sure to be a bad head gasket, but there is no coolant loss at all and it doesn't look terribly contaminated. I would like to be sure before I yank the head obviously.

  3. #3
    JT jpt7779's Avatar
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    Are you 100% sure that you are getting water from the pump ok? The hose in the picture has split on several of us with this ski. BRP came out with a stronger reinforced hose after many complaints. It is possible your supply hose has a split in it or loose clamp and no one has discovered it. Raise the iBr gate, look at the left side of the pump and you will see this hose going from the pump to the iBr thru hull fitting. You guys have replaced everything else……..

    Click image for larger version. 

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  4. #4
    Quote Originally Posted by k-dub View Post
    I'm having a similar issue. I can run the boat all day but if I run hard for a time it throws the engine over temp alarm.

    I have read that this is sure to be a bad head gasket, but there is no coolant loss at all and it doesn't look terribly contaminated. I would like to be sure before I yank the head obviously.
    Hi k-dub,

    Sorry to hear you've got a similar issue, very frustrating.

    My mechanic thought it might have been a bad head gasket too. He replaced it after realising the original one was fine.

    Coolant and oil has been replaced. There's no cross-contamination of these fluids nor are they leaking from the engine.

    Regards.
    Last edited by Tangles; 10-04-2014 at 05:48 AM.

  5. #5
    Quote Originally Posted by jpt7779 View Post
    Are you 100% sure that you are getting water from the pump ok? The hose in the picture has split on several of us with this ski. BRP came out with a stronger reinforced hose after many complaints. It is possible your supply hose has a split in it or loose clamp and no one has discovered it. Raise the iBr gate, look at the left side of the pump and you will see this hose going from the pump to the iBr thru hull fitting. You guys have replaced everything else……..

    Click image for larger version. 

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ID:	343415
    Hi jpt7779,

    Mechanic has confirmed engine is not overheating but I will ask him to check that water hose to make sure it's not leaking or split.

    Thanks.
    Last edited by Tangles; 10-04-2014 at 09:24 PM.

  6. #6
    Hi everyone,

    Finally worked out what was responsible for this issue, the CLCS ride-plate. The coolant circulating through it was flowing well, a little too well (ie. quickly/freely). One of the internal channel walls/seals had broken/split which created a shortcut for the coolant, allowing it to flow through the plate too fast, not allowing it to cool down enough, causing the engine to overheat. Below is a diagram of a CLCS ride-plate with its top removed.

    After my ski's ride-plate was replaced I took it for a water test. Rode ski for about 20 minutes at full speed (WOT) and the engine temp displayed on the dash remained between 89-90 degrees - perfect !

    So, if your engine ever overheats remember this thread (and the other one I created). The fact that your ride-plate might be flowing freely is not enough, the coolant has to remain inside these plates for a certain length of time for it cool down properly.

    Thanks for your replies - all the best.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Last edited by Tangles; 12-12-2014 at 01:21 AM.

  7. #7
    JT jpt7779's Avatar
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    Good find!

    All the Open Loop cooling guys are saying, "won't happen to me".

  8. #8
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Tangles View Post
    ... Mechanic has confirmed, by installing an aftermarket engine temperature monitor/gauge and by pointing an infrared heat gun at engine after alarm/buzzer sounds, that engine is not actually overheating. For some reason, only the displayed temp on the dashboard is indicating temperature is high.

    ... mechanic is close to running out of ideas ...
    Quote Originally Posted by Tangles View Post
    ?.. Finally worked out what was responsible for this issue, the CLCS ride-plate... One of the internal channel walls/seals had broken/split which created a shortcut for the coolant, allowing it to flow through the plate too fast, not allowing it to cool down enough, causing the engine to overheat...
    So the engine really was overheating, and the mechanic mis-diagnosed, correct?

    Any idea what caused the ride plate to internally fail?

    Was it simply coincidence that you first noticed the overheat after the sinking, or did something happen during/after the sinking that hurt the ride plate?

  9. #9
    Quote Originally Posted by jpt7779 View Post
    Good find!

    All the Open Loop cooling guys are saying, "won't happen to me".
    Hi jpt7779,

    Yep the open-loop guys are probably saying that. No brand/design of ski is perfect, they all have flaws and issues.

  10. #10
    Quote Originally Posted by K447 View Post
    Quote Originally Posted by Tangles View Post
    ... Mechanic has confirmed, by installing an aftermarket engine temperature monitor/gauge and by pointing an infrared heat gun at engine after alarm/buzzer sounds, that engine is not actually overheating. For some reason, only the displayed temp on the dashboard is indicating temperature is high.

    ... mechanic is close to running out of ideas ...
    Quote Originally Posted by Tangles View Post
    ?.. Finally worked out what was responsible for this issue, the CLCS ride-plate... One of the internal channel walls/seals had broken/split which created a shortcut for the coolant, allowing it to flow through the plate too fast, not allowing it to cool down enough, causing the engine to overheat...
    So the engine really was overheating, and the mechanic mis-diagnosed, correct?

    Any idea what caused the ride plate to internally fail?

    Was it simply coincidence that you first noticed the overheat after the sinking, or did something happen during/after the sinking that hurt the ride plate?
    Hey K447,

    Correct, the 2nd moral of this story (for me) is never to believe everything your mechanic says, no matter how well you think you know him. Whilst I didn't remind him he said that to me (ie. engine's not actually overheating) I'm sure he's now aware of the egg on his face.

    When the exhaust manifold's cooling hose came off the IBR actuator (because clamp wasn't tightened) I was riding in pretty big seas. I can only imagine the huge chop must have damaged the ride plate internally. Or it's just an amazing coincidence it happened on the same day as the sinking.
    Last edited by Tangles; 12-13-2014 at 02:09 PM.

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