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Overheating - 06 vlx


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Hey Gang, could really use youre input on this one:

Put around 10 hours on so far this season with no issues, until the other night just drove over to riding area and hitemp alarm sounded at 202 degrees...

-383 hammerhead with ~120 hrs, no previous issues

Generally idling is okay, even fairly moderate idling around 1500rpm. Stays "around" 160 but then creeps up into 170s/180s when higher rpm. Will cool back down to 160 when throttle is brought down to ~1200-1500rpm again. Any load will cause a spike near 200 degrees.

Pulled tranny cooler hoses and inspected tranny cooler - looked clean

Just installed new impeller at begin of season so didnt think it was that

Saw some minor debris in perko flush pro (see through) - some pine needles (2 small pieces)

Some debris (pine needles) in water but not too bad - thought might have plugged up tranny cooler or tstat.

Pulled tstat lines and they were clear

Suspected tstat so pick one up and put in new one - old one looked okay, housing was clean

Ran up and still had same overheating issues.

Pulled impeller and it looked fine.

Blew air through intake hose (vdrive exit to impeller housing) was fine

blew air through impeller to tranny cooler hose was fine

The heater does not push hot air even after up to 160 degrees or higher - but blows cold air.

Any help? kinda stumpped here.

Cheers,

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I would take the hose off at the bottom of the tranny cooler and start the boat for just a moment to see what level of flow you are getting from the impeller. If all good then re assemble and start the motor and look for a small leak on the cooling system. Possibly a leaking raw water pump ? It sounds to me like the system is sucking air. If it's staying cool at idle but overheating at higher speeds it's likely sucking air into the system.

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I can't recall if our boats have an engine water pump (as opposed to the raw water pump). Yours may be bad or clogged. Also check the sea strainer on the bottom of the boat. Start pulling hoses off and try running some air or water through each section looking for a clog.

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If the impeller looks good it could be the housing that holds the impeller. It has a drive shaft that spins the impeller maybe you sheared that? The only other thing it could be is your thermostat if all the lines are clear.

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OneMoreSet:

Have you read my issues on my boat of 'conditional' overheating. Although mine sounds opposite of yours (mine overheats at idle...), I'm starting to think it may be the engine circulating water pump. I've taken the same steps as you, and still have my issue.

I'm trying to obtain the 'symptoms' that a marine engine will exhibit with a failed engine water pump. With the lines clean, coolers/ strainers clean, no air leaks in water system, a new t-stat, a new raw water pump impeller, it's leading me to an engine water pump. Just before I tear into the front of the engine to change it, would like to undertand the symptoms of a failed engine water circulating pump.

Maybe a failed engine water pump can exhibit both the conditons?????

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I can't remember what my bu has, but for the bu's that have a raw water impeller with a engine water pump here's how it works... The raw water pump is a positive displacement pump with a closed waterway and will develope vacuum to suck in the raw water and prime itself. The engine water pump is different and is an open vein centrifugal pump and will not prime itself that's why there's a raw water pump. However, if the engine water pump is primed it will keep it's prime and continue to pump until the motor is shut down. I've worked on many fleet vehicles and others and never had a motor water pump stop pumping or pump less then it should. They will develop leaks in the seals or bad bearings, but that's it.

If the heater is not getting hot there's a blockage or restriction somewhere and you'll just have to hunt it down. It could even be an accumilation of mud in the block... If it has knock sensors or drain plugs on the lower sides of the block try opening these with water running in your driveway.

WOW, I just saw the video on another overheating post and was amazed at cracked impeller on the engine water pump. The one thing that we deal with in open cooling systems is that rocks, sand and other debri can be sucked into the cooling system and if it binds the impeller enough the force will strip or break the impeller, whereas, on a vehicles closed cooling system the debris issue isn't a problem.

Edited by scfdfireman
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Thanks for the replies guys, appreciate it.

I was suspecting the circulation pump as well, but part of me just thinks thats a long shot. I know of cars if the circ pump goes it starts to leak or has some bearing sounds as fireman points out above.

Funlife I did read yours as i scoured the forum for answers. The closest one i found was one which had the same overheat problems and cause was mud blockage in block. Mine seems really clean and to me if its twigs or something it should be before the impeller or at tranny cooler - those are the tightest spots to collect stuff and the soonest in the loop.

The other thing i can think of is a malfunctioning temp sensor / sender. This is also unlikely though - it does show a reading and you can see it creeping up.

I pulled off a bunch of hoses and havent seen any debris buildup.

i checked the thru hull and it seems clear, the hose between the flush pro and the vdrive are clear, hose between vdrive and impeller seems file.

impeller pulled - looks fine

hose between impeller and tranny cooler seems good.

tranny cooler was clear

hoses to tstat housing and to circ pump fine

replaced tstat - thought this was the original issue - tested the old one and it turned out to open fine.

my biggest clue is the heater isnt getting warm - it has to be either 1) no flow or 2) engine isnt hot enough

im thinking its flow because heater from shower is getting hot enough

i pulled the supply hose for the heater off the block (near tstat housing) and while running it flowed water out, however with the hose on it doesnt "FEEL" like any water is flowing if you squeeze down on it.

its an '06 and from what i read the factory incorrectly installed the heater "Y" pipe - its installed after the impeller on mine and should be before the impeller.

What im thinking here is that the return flow is encountering resistance when flowed back to the return line and if it doesnt have enough pressure cant start the flow.

its been like this hooked up and working fine however so this shouldnt be the cause.

I was wondering if the circ pump isnt putting out enough pressure to flow the heater.

I pulled the shower hot line which is tapped off the block near the starter. it flows good amounts of water as well.

Pulled the quickconnect crossunder tubes which connect the exhaust headers and they flow.

Anyone have a diagram showing how the water flows?

do the exhaust headers get fed the whole time, or only when tstat opens??

thanks for the help, and keep any suggestions rolling.

Cheers,

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Just for the heck of it try taking off the hose that returns to the motor from the heater. See what's flowing out of the heater... The veins in a heater core are small and may be plugged with sand. If not, it may also be a plumbing ussue and the site should have info on how it should be plumbed.

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this a vdrive or dd?

i'd head in the direction suggested by grandude: with a cold engine remove the hose at the trans cooler and start the engine. should have LOTS of water flowing out that hose. spin the rpm up to 1800 rpm and you should have even more water flowing. while at idle i'd even be tempted to squeeze that hose to add back pressure and see how it acts. of course you are going to be careful near the moving machinery.

i'd also take another look at that thermostat to insure it is installed correctly. the only reason i'd suggest it is because it would be easy to put them in upside down.

let us know how this story ends.

edited an addition. you mentioned the possibility of "malfunctioning temp sensor / sender". consider CAREFULLY, using the back of your hand, touching the exhaust elbow when your gauge is telling you the temp is 160°. i often use the exhaust elbows to lean on while reaching into the bilge. you should be able to keep your hand on it for at least a few seconds at that temperature. try that again when the temp is at 200° and your hand will get too hot immediately.

Edited by tvano
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Take the heater out of by removing the supply and return lines. Just get a jumper hose to connect the supply and return. That then removes the heater from the equation. The heater only gets hot when the boat is running at about 1500 rpm for me.

I'm not convinced the heater can over heat the boat just yet.

When you run it with a fake lake does water pour out the exhaust flaps behind the boat?

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Take the heater out of by removing the supply and return lines. Just get a jumper hose to connect the supply and return. That then removes the heater from the equation. The heater only gets hot when the boat is running at about 1500 rpm for me.

I'm not convinced the heater can over heat the boat just yet.

When you run it with a fake lake does water pour out the exhaust flaps behind the boat?

you need the Y pipe mod. Then it's hot at idle!

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you need the Y pipe mod. Then it's hot at idle!

I'm not sure what the y pipe mod is?

I've just used a jumper hose to connect the intake and return when my buddies heater was leaking. You just have to make sure you don't get it around any moving parts.

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I'm not sure what the y pipe mod is?

I've just used a jumper hose to connect the intake and return when my buddies heater was leaking. You just have to make sure you don't get it around any moving parts.

If you're not getting hot air while idle, install this:

FittingYlowRPM_LG.jpg

It can be found here. It pulls more water through the heater at idle and came stock on later model BU's. Sorry for the thread jack.

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Hey guys, thanks again for all your input.

I'm still working on it here and working through all the suggestions and a few more.

Although the heater is not getting hot I dont think it itself is the cause of the overheating. What im thinking is if the heater is packed full of crap and doesnt allow water to flow its just like a boat without a heater installed and they work fine.

It is a clue though i think that its not heating up that somewhere there might be a restriction, even if its not in the heater itself.

I'll keep you guys posted.

Cheers,

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so here's an update - still no fix, just more questions.

So a quick recap we had an overheat situation that we would get upto ~200o at around 2500rpm very quickly and idle around 165o. We did the usual check, impeller, tranny cooler, tstat. All were good and we changed the tstat. No Change. Tested original tstat and it was fine.

So we moved onto:

Pulled the hoses from the perko flushpro all the way to the impeller.

Ensured hoses were clear by pushing another hose through them.

Checked impeller - was fine.

Checked hoses from impeller to tstat housing.

Checked tranny cooler and it was clear.

Blew through Header hoses from tstat housing to headers.

Blew through under engine quick connect for headers..

Checked both knock sensor plug locations removed and poked around - found nothing.

Hot shower port has water flowing from it.

Tested water pressure at exit of impeller with hose off and was flowing really good even with resistance in place.

While I was at removing hoses I moved the factory installed heater return "Y" from after the impeller to before the impeller - as per heatercraft and others around on the web.

One thing i noticed during overheat issue was the heater didnt work. This seemed to fix the heater not working issue, but still have the overheat situation. I didnt change this to resolve the overheat, just while I was at it.

After all this i ran it up on the perko flush pro - it ran at idle to around 140o instead of around 160-165o.

i ran it at 1250rpm on perko and that brought it upto 160-165 - encouraging...

i ran at 2000rpm on perko and it got upto around 175o.

Tested at the lake - lake temp 63o

at idle was around 140o, running around 2000rpm was at 160-165.

Running at 3000rpm it climbed to around 175-180.

So this was an improvement as previously the temp running like this would have put us to 200o

We noticed that while the engine read hot at 175-180 the exhaust manifolds were fairly cool - I could hold my hand there indefinetly. I know previously running at 160o it would be quite warm to the touch - so this seemed off...

We swaped out the temp sensor as i had a tough time getting a proper impedance reading which indicated it might be failing.

That didnt work either... Generally the same readings.

We dug around the engine and felt that the engine block seems to be getting warm but the exhaust headers are staying cool.

If you look at the tstat housing there are 4 hoses connected - 1 from impeller in - 1 to the circ pump, and 2 exit to the manifolds.

We thought there must be an issue with coolant getting from the engine to the exhaust manifolds.

Seemed like tstat - stange since it was brand new and the last one was fine after testing...

Yanked the tstat out and ran without the tstat in.

I figured it should run the same after to temp as essentially it works as if the tstat would be open.

NOPE - we couldnt get it to heat up - nothing else changed - with no tstat temp was at 100-110o !!

Wow didnt expect that - the hotest it got was 110o - and that was idling. it cooled down at high load to 100o

We ran at 3500rmp with wedge down for 5 min and it didnt come up - stayed at 100....

This to me would indicate no lack of water flow or cooling - but an issue with the tstat.

i came home and heated up a pot of water to check the tstat - but it did open up. Not sure at what exact temp but it did open & close correctly... So strange.

The tstat is marked as 160o and looks identical to the factory unit.

Thought perhaps I put it in upsidedown but checking the web seems it was incorrect- pointy end up towards top of housing.

Any thoughts?

I did notice after using the perko it seemed to let in some air - could see bubbles coming in - but i tightened it down really good and then it didnt seem like any issues anymore.

Where to go next - any ideas??

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I could be wrong, but I think there are 2 temp gauges. One is for the ecu and the other is for the dash gauge. Did you check both of them? It might be that your engine is the correct temp, but the dash gauge is off. Just a thought.

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It seems like a flow issue if the block seems hotter than the manifolds and the symptoms disappear when removing the thermostat. Why not try and remove the flushpro and run a test? Just replace it with straight nipple and a couple of clamps.

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UPDATE - Problem identified !!

Thanks for all your help diagnosing.

Turns out its the engine circulation water pump.

We were starting to suspect that something was preventing the tstat to open since engine was getting hot but manifolds were still cool.

A leaking headgasket causes the tstat not to open because of air/bubbles preventing the water from touching the bottom of the tstat. We did a comp test and confirmed good compression - so definetly no leaking head gasket.

Talked to some local boat techs and generally suggested a blockage.

Talked to Indmar tech and he thought it could be circ pump.

Didnt realy want to yank off the circ pump just to see it was okay and have the nice marine paint crack off everywhere and need new gaskets. Generally these never fail and if they do its the bearings (which you can hear) or seals which you can see a leak.

We tried to use an inspection camera but unless you have an ultra thin head on it you cant see what you need on how the circ pump is designed.

So what we did was remove the drive belt and open the top port on the circ pump and then i turned the circ pump by hand. My theory was that i can spin the pump by hand and if there is an impeller working inside it will move some water.

I spun it and absolutely no water movement. We also happened to have the tstat housing off and could see the engine water level there too and absolutely no flow. After seeing that we felt confident it was the circ pump.

Someone here posted a pic & video of a failed circ pump - shake it and if it makes a noise the impeller is broken. Sure enough took of the pump and it rattled like a cow bell.

Opened up the back side and .... cracked in half impeller!

<< Cant seem to post pic>>

After talking to Indmar and seeing the pump it makes sense that a broken impellar plate can restrict any waterflow.

One of the big clues was the heater stopped pumping hot air even thought the temp guage was high.

Water restriction prevented heater from being fed.

I wanted to get a solution back on here because I found a few other posts here and on the web that were eerily familiar and would have loved to see the outcome.

Cheers!

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  • 9 months later...

UPDATE - Problem identified !!

Thanks for all your help diagnosing.

Turns out its the engine circulation water pump.

We were starting to suspect that something was preventing the tstat to open since engine was getting hot but manifolds were still cool.

A leaking headgasket causes the tstat not to open because of air/bubbles preventing the water from touching the bottom of the tstat. We did a comp test and confirmed good compression - so definetly no leaking head gasket.

Talked to some local boat techs and generally suggested a blockage.

Talked to Indmar tech and he thought it could be circ pump.

Didnt realy want to yank off the circ pump just to see it was okay and have the nice marine paint crack off everywhere and need new gaskets. Generally these never fail and if they do its the bearings (which you can hear) or seals which you can see a leak.

We tried to use an inspection camera but unless you have an ultra thin head on it you cant see what you need on how the circ pump is designed.

So what we did was remove the drive belt and open the top port on the circ pump and then i turned the circ pump by hand. My theory was that i can spin the pump by hand and if there is an impeller working inside it will move some water.

I spun it and absolutely no water movement. We also happened to have the tstat housing off and could see the engine water level there too and absolutely no flow. After seeing that we felt confident it was the circ pump.

Someone here posted a pic & video of a failed circ pump - shake it and if it makes a noise the impeller is broken. Sure enough took of the pump and it rattled like a cow bell.

Opened up the back side and .... cracked in half impeller!

<< Cant seem to post pic>>

After talking to Indmar and seeing the pump it makes sense that a broken impellar plate can restrict any waterflow.

One of the big clues was the heater stopped pumping hot air even thought the temp guage was high.

Water restriction prevented heater from being fed.

I wanted to get a solution back on here because I found a few other posts here and on the web that were eerily familiar and would have loved to see the outcome.

Cheers!

Everything you say here mimics what I have going on right now... wow. I'm going to remove the belt and test as well. Thanks! When you moved the pump by hand were you able to "hear" the broken impeller? I moved mine by hand as fast as I could, a little bit of water pumped out the top heater port... so it's hard to say weather its good or not...

Edited by wakeparadise
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