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Yanmar marine 6lya-stp Needs Flush (or more)!! #5165853 07/19/19 09:48 PM
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Capt Online Content OP
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I am dealing with a customer boat 2007 Yanmar 6lya-stp 370hp with a neglected cooling system. I tried to drain coolant from block petcock and not a drop.. after inserting 6'' screw drivers into hole came nothing but brown hard sludge... not a drop of liquid! Upper coolant reservoir & heat exchanger top showed rusty brown water, not pretty.

It should be flushed several times to operating Temp & filed with a O.A.T. ELC or Dexcool per Yanmar specs.

What would be a good product to remove sludge buildup???

This engine ran 30 hrs at 80% (2800 rpm) power 400 miles just a few months ago @ 170F with no issues, but I think its a ticking time bomb...

any suggestions?

Thanks,

Capt

Last edited by Capt; 07/19/19 10:02 PM.
Re: Yanmar marine 6lya-stp Needs Flush (or more)!! [Re: Capt] #5165866 07/19/19 10:03 PM
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Rand Offline
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non marine engines I'd use prestone super flush or citric acid.

but I dont work on closed system marine engines...


2019 Jeep Cherokee Trailhawk 2.0T
Re: Yanmar marine 6lya-stp Needs Flush (or more)!! [Re: Capt] #5165883 07/19/19 10:35 PM
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mattwithcats Offline
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Go by a hardware store, pick up a box of Tri Sodium Phosphate, TSP...

Add 1/2 to 1 tablespoon per gallon of system capacity...

Also consider installing a coolant filter if possible...

https://en.m.wikipedia.org/wiki/Trisodium_phosphate

Last edited by mattwithcats; 07/19/19 10:37 PM.

2009 Smart Pure
Pennzoil Platinum Euro 0W-40, Wix XP 51356 filter, 45 mpg...
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Re: Yanmar marine 6lya-stp Needs Flush (or more)!! [Re: Capt] #5165960 07/20/19 01:57 AM
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Linctex Offline
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White vinegar and citric acid are mentioned al the time.

Cascade automatic dishwasher soap also cleans well.

A closed loop system marine engine shouldn't be too much different than a car/truck.

Does the big Yanmar use dry sleeves or wet sleeves?


"The evidence demands a verdict".
(Re:VOA)"it's nearly impossible to actually know the particular additives that are in there at what concentrations."
Re: Yanmar marine 6lya-stp Needs Flush (or more)!! [Re: Capt] #5166115 07/20/19 08:47 AM
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bullwinkle Offline
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I'm guessing something bad has happened-major cooling system leak through the heat exchangers-or worse?


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Re: Yanmar marine 6lya-stp Needs Flush (or more)!! [Re: Capt] #5166308 07/20/19 12:13 PM
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Capt Online Content OP
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Not Sure about the sleeves. I believe the issue is from old coolant or possibly mixing of incompatible coolants as I noticed a jug on the boat with a missing label, who knows... We have not noticed any coolant loss or gain so hopefully the system is still intact, I will probably do a leak down test. I will start with an automotive radiator flush and report back. Thanks -capt

Re: Yanmar marine 6lya-stp Needs Flush (or more)!! [Re: Capt] #5167086 07/21/19 09:56 AM
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roadrunner1 Offline
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FleetGuard make a product, Restore/Restore+ for cleaning cooling systems. I've used it and it works very well.


'15 F350 6.7
Re: Yanmar marine 6lya-stp Needs Flush (or more)!! [Re: roadrunner1] #5168472 07/22/19 09:28 PM
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Capt Online Content OP
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Hello all, I was able to clear the clog with compressed air and a few ounces of mush blew out along with grayish brownish water, All drained out. Added some tap water and ran engine for 20 mins (165 F holding) and cleanish water came out, no sludge. Drained and added tap water and 2 bottles of Zerex super cleaner, ran for 2 hours (160 f holding), took sample from low petcock (pictured). Will run engine tomorrow for an hour and take another sample. I will probably drain, flush with distilled water & add Dexcool tomorrow. Yes I did notice a 5 F degree drop after adding Zerex super cleaner. - capt

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