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350 Monsoon "conditional" Overheating


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21 minutes ago, wakeparadise said:

I just consulted with my mechanic, he says it’s most likely the raw water pump. It may look like it’s moving a lot of water at idle but it could be just an illusion. The other thing he says is to check where the water exits the block; if that’s partially blocked it would affect the needed-flow of water. Check the elbow of the 90 degree valve, make sure there’s no blockage along that route. 

You could disconnect the hoses from the thermostat housing to the exhaust manifolds, at the manifold, and run the engine for less than a minute with the water dumping into the bilge to check flow.  At this point you could check the water temp to see if it's hot, is bypassing the motor and is cold.

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Another clue might be the 210 degrees is suspiciously close to the boiling point of water (not under pressure, like at idle).  That's the max temp liquid water can be.

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Update, and clue...

As many are saying parts (impeller, pump, thermostat, temp switch, etc.), I've changed them all, and condition does not change (note, I've lived with this for about 4 years intermittently, just seems worse now).

Tonight, i checked and cleaned every part up to and including the thermostat housing. After about two hours of removal and reassembly, all good.  Cleaned the intake port, heater port and temp switch port on intake. No kidding, took it all off and checked and cleaned. No issues found, Put it all back together.

Here is my latest question, and theory / clue....

I was poking around with the infrared thermometer, when rising temp issue occurs.  I recorded all the temps at the water impeller pump, all the way through to the thermostat housing, and each of the lines of the housing, and the intake.  Surprisingly (at least to me) there is a big difference in the temps on each of the lines coming from the housing, and the difference grows as the temp rises. Temps are all about 100' after trans cooler and hold steady. 100' going into housing (front right). 110' leaving t-stat housing to circulating pump (front left). 

The middle outlets- things get a little crazy...  Normally (when boat temp is 160') Temps on lines from the housing to the upper cat exhaust manifolds are about 118' - 125', yet when boat temp is rising on gage, these ports go to 175' - 190'!!!!!!  (The back ports that go to the lower exhaust stay about 120' and don't change much)

So, why do these hoses rise in temp when the boat (gage on dash) temp rises?  

I now believe that when the boat is at temp (160'), all works well. Shutting it down and idling, the water (and possibly hot air / steam) from the cat exhaust manifolds is draining back to the thermostat housing, as at idle, there is not enough water pressure to push the water above the thermostat housing, as the thermostat is open, and the water is being consumed by the engine!!!  The hoses from the thermostat housing are about 2" - 3" lower than the connection on the cat manifold, so all that water needs to be pushed into the cat, with the engine and lower (rear outlets on the housing) pulling water capacity from the housing. Or looking at it differently, the water and air/ steam from the cat exhaust will get pulled into the thermostat housing at idle....

Is it possible that something is missing between the thermostat housing and the cat exhaust? While I do winterize the boat myself now, the marina winterized it for me the first 3 years of ownership. Any possibility that upon winterization, some "helper" pulled a part from this hose / connection and did not replace?

So, would like to know if your monsoon hookup to the upper exhaust goes from the thermostat housing with a hose, clamped on the housing, to the brass fitting on the back of the cat exhaust direct, with no check valve, or anything that would prevent the backflow of water (or air/ steam) from the cats back to the thermostat housing. 

Again, appreciate the help, and all of you giving me your thoughts. I now believe we are close to solving.... 

 

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Based on what I've discovered last night, and the use of the infrared temp gun, along with my focus on the water coming off the cat exhaust, I think I've (along with others to varying degrees) have come to the conclusion that this is a design issue (why I've had it so long, and through all the part changes) as to how the plumbing is from the thermostat housing to the exhausts.  I plan on making the plumbing change once I get the parts required, and I will update all on this.  Clearly a tough one to solve, yet he info was right here on "the Malibu crew":  Click on the link below, and will show the upgrade to the cat exhaust plumbing-

 

Edited by funlife
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Yes, the image in the EXT Cat Cooling upgrade post with the split hose is from my RLXI 2011 350 Monsoon.

No regrets after the cooling upgrade.

Only picked it looking at followng year models with the same engine & noticed the different routing of the hoses.

Bit of investigating led me to the upgrade. Even asked Indmar & received a reply from Lary about some of the newer models having metal plumbing as this was only a nice change not a must change, the rubber hoses are fine

We don't have any freezing temps in sunny Queensland Australia so wintererizing is not a concern, more the opposite when the water/lale temp gets up.

You wil find after the upgrade you can put your hans on the CATS after a slow surf run when the enginis under the most load, they will be about as hot as a cup of black coffee.

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1 hour ago, funlife said:

Well, that fixed it. A design 'flaw" issue from Indmar that the fix was known since 2012/2013.  

After the plumbing change, the boat runs at 143 at ski speeds, and is stable. Even sitting with the motor running at idle, does not get above 160.  (Cat) Exhaust manifolds are MUCH cooler! Even after a 15 minute run at ski speeds, infrared showed manifolds at 125'. Could even put your hand on them - about the temp of a hot cup of coffee...

A few years of issues with overheats.... Three weeks of pursuing....  Finally have the issue under control!!!

 

I’d be concerned about it running at 143F at speed, almost seems like the thermostat isn’t even given a chance to do its job and regulate it at 160. Doesn’t that seem off to you?

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With a 160' Thermostat, it does.... Yet, I'm going with it, as Indmar recommends this redesigned type of plumbing for all boats with ETX Cat Exhaust systems. I notice no degradation of performance, and heater on boat works fine. As it's new, I'm going to watch it closely for the next few weeks, and keep my Infrared Thermometer close by. Shooting all areas of the engine and exhaust manifolds so far, nothing is showing hot areas or hot spots.

It certainly runs cooler, and given the option, sure beats the boat alarming after a ski run, and seeing the engine temps in the high 190's.  Those days are now behind me.

I do plan on watching fuel usage, etc. Even with the 160' Thermostat, it's clear that the engine is getting water to keep cool.

 

 

 

 

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Talked to Indmar technical support this week. Said it is OK at the 130' temp, yet not normal. There was a recommendation on the old way of plumbing the manifolds to drill a 1/4" hole on the inside of the thermostat housing (between the internal ports) to try and cool down the water. He thinks this was done on my boat. He said to plug it, or replace. Heck, I'm into it this far, so new Thermostat housing on the way.  

Indmar Tech said after replacing housing, and if I still have the engine running cooler than 160, we'll look for the 'next step'. 

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  • 5 years later...
On 8/18/2018 at 1:59 PM, funlife said:

Talked to Indmar technical support this week. Said it is OK at the 130' temp, yet not normal. There was a recommendation on the old way of plumbing the manifolds to drill a 1/4" hole on the inside of the thermostat housing (between the internal ports) to try and cool down the water. He thinks this was done on my boat. He said to plug it, or replace. Heck, I'm into it this far, so new Thermostat housing on the way.  

Indmar Tech said after replacing housing, and if I still have the engine running cooler than 160, we'll look for the 'next step'. 

Hi, I'm Josep from Spain. My boat is the Moomba LSV 2008 and I have the same issue. Could you tell me about the "next step"?

Best;
Josep

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