Gunk in cylinder head

[markrlr300]

Hello, when replacing my thermostat I noticed white gunk down in the head. Is there any way to flush this out? This is a 75 hp Yamaha 4 stroke 2006

[robert graham]

You can run the motor in a 55 gallon drum with some chemicals like Salt-a-Way or other similar cleaning products....Google/research the subject...a good bit of information is out there that you may find helpful. Good luck!

[markrlr300]

Thanks Robert! Ill check it out. I have the drum just wasn't sure what to use.

[TownsendsFJR1300]

Just curious.

Is the engine used in salt water and if so, flushed religiously after use?

[robert graham]

It'll take an acidic solution circulating through the passages to dissolve those white/tan salt/calcium/mineral deposits....they may show up as a creamy foam on the surface of your solution in your drum....hopefully these deposits will dissolve and not break off in pieces/chunks that can stop up the passages.....the water in your drum will get hot from the exhaust and keep a freshwater hose to replace any lost water. The trick is to remove deposits with a minimum of metal/aluminum removal(especially the threads of nuts/bolts/fasteners/tapped holes, pin holes in aluminum)....bottom line is in my opinion is that most motors will have some deposits in the cooling system but if they are not causing overheating so other problems it may be best to just leave them alone, because there will be risks to any chemical cleaning. But I understand that once you look inside there and see them it's sorta hard to forget about them....Good Luck!

[TownsendsFJR1300]

I posted these links on another thread, it may help you:

http://www.yamahaoutboardparts.com/f...g-th19434.html


http://www.yamahaoutboardparts.com/f...m-th23666.html

[scofflaw]

Ridlyme = watered down version of hydrochloric acid at about 20 times the price

[TownsendsFJR1300]

Ridlyme = watered down version of hydrochloric acid at about 20 times the price

What percentages of each, water and acid, is safe to use without damaging the engine?

[robert graham]

It's about the strength of the acid(pH), temperature of the acid(the exhaust will heat it up a good bit quickly), the length of time the acid solution is circulated, the composition of the deposits (pure calcium is fairly quickly removed...others maybe not so fast)....A gallon of muriatic/hydrochloric acid from Home Depot added slowly to the 55 gallon drum of warm circulating water and observe the action on the surface of the water for foaming signs of deposit removal....possibly turn motor off long enough to remove thermostat plate to check activity....turn motor back on if required for additional cleaning.....After finishing be sure to neutralize the acid by adding and circulating several boxes of bicarbonate of soda....You want the least amount of strength/temperature/circulation time to give the desired cleaning effect....

[scofflaw]

I've used straight muriatic acid thru the t stats for 10 minutes with good cooling results and no negative results 50 hours later.

Obviously a crap shoot with nothing scientific behind it.

What I can say with some testing, the acid will completely dissolve any kind of marine life, barnacles and such, in a matter of seconds. Also soaked a pencil anode for over 4 hours with minimal reduction in mass.

[rodbolt17]

muratic acid EATS Aluminium.
roll da dice.

[TownsendsFJR1300]

muratic acid EATS Aluminium.

That was my point...

Straight muratic acid is cheaper but mixed too strong, as you stated, roll the dice.

The pre-mixed is less likely to cause issues vs using too strong, too long.. You want just enough to clear the passages of junk/salt, BUT not eat the inside of the engine out...

The one link, the LU is removed and is electrically pumped thru the engine at a con*****ed rate(and caught in a container -re-circulated). You should be able to see progress and when to stop, vs ???

Just mt 2cts...