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MDW

Monsoon 350 overheating at idle

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MDW

I've recently bought a 2012 Wakesetter with the Indmar 350 Monsoon (Salt Water Series), 105 hrs on the clock....after a couple of teething problems - namely having to replace the alternator. However,

It and has recently started to alarm with high coolant temp when running at v slow speed/idle. When running normally the temp sits at about 170 but as soon as I slow down for no wake zones/marina areas etc it climbs rapidly to 200+ and the ECM system kicks in and limits the throttle until the temp reduces. I'm operating the boat in the United Arab Emirates where the water temp is 90F. 

I've also noticed that the coolant level drops on a daily basis after it has been topped up

I'm no mechanic and there isn't a specialised Indmar dealer here, I was wondering if anyone has any insight to possible problems so that I can 'steer' the local boat maintainers in the right fault finding direction.

Thanks

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tvano

welcome to tmc

find / repair the coolant leak and replace the impeller.  

both jobs should be easy for a beginner.

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Gavin17

Yep, he's right. 

Heating up at idle is the textbook symptom of a worn impeller.  Hopefully they're not too hard for you to source. If you have to order one from abroad I'd order several and stock up.  You'll want to replace it every 1-3 years.  

I think your system uses raw water to cool the exhaust manifolds and coolant to cool the engine block.  To find the coolant leak I'd just clean and dry everything as best you can and run the boat while looking for drips with a mirror and flashlight.  Once you find the leak hopefully it's as simple as tightening the faulty clamp or replacing the faulty hose.  If the leak turns out to be something more complicated take photos and post them on here so we can help more. 

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oldjeep

If you are not seeing anywhere that you could be losing coolant in the bilge then check the heat exchanger for internal leaks

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Woodski

@MDW:  Another item to troubleshoot would be the heat exchanger.  A blocked raw water entry side along with as noted a worn or defective impeller will cause low engine speed overheating.  The coolant could be escaping via a breach in the heat exchanger between raw and closed circuit passages.  You mentioned salt water which is very corrosive to many of the components.  If you don't already have them, salt water anodes may be a good option to slow corrosion issues. 

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stevod83

It could also be the raw water intake hose.  I fixed the same overheating problem by replacing it.

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MDW

Guys - thanks for your input/suggestions. We traced the coolant leak to the plastic elbow joints on the bottom of the exhaust manifold - changed them to brass fittings and also changed the impeller (I don't think it had been changed in 3 yrs despite only having 100 running hours). Ran the boat for about half an hour yesterday - incl a prolonged period at idle and the temp didn't rise above 165F - depsite the sea water being 90F!!

Hopefully we can finally get out and do the fun stuff now.

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Air Tahoe
2 hours ago, MDW said:

Guys - thanks for your input/suggestions. We traced the coolant leak to the plastic elbow joints on the bottom of the exhaust manifold - changed them to brass fittings and also changed the impeller (I don't think it had been changed in 3 yrs despite only having 100 running hours). Ran the boat for about half an hour yesterday - incl a prolonged period at idle and the temp didn't rise above 165F - depsite the sea water being 90F!!

Hopefully we can finally get out and do the fun stuff now.

Glad you got it fixed!

Edited by Air Tahoe

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