Acid flushing vs Poppet valve (PCV)

[DannyMart]

even at 110 the stats will close off, better to remove while circulating the chemical

Like the earlier attempt, I will remove the thermostats.

[BQUICK]

i put hoses and fittings on the tstat housings going to a T between the heads. Connect garden hose to T and flush from top down. Basically a back flush. Seems to work well but T stats need to be removed.

[DannyMart]

i put hoses and fittings on the tstat housings going to a T between the heads. Connect garden hose to T and flush from top down. Basically a back flush. Seems to work well but T stats need to be removed.

What were the fittings on the T stat covers you used?

[cleddau1]

Seawater contains a near saturated solution of Calcium Hydroxide and is slightly alkaline. Calcium Hydroxide demonstrates inverse solubility eg it is only half as soluble at 70 degrees Celsius as it is at 20 degrees Celsius and thus precipitates out in a warmed up outboard. Calcium Hydroxide solution is corrosive to Aluminium so the crud in the cooling passages is mostly Calcium Hydroxide with some contribution from your engine. Lowering the PH increases the solubility but a strong acid will attack Aluminium also so flushing with a weak acid such as vinegar makes sense but a cold solution should be used. In Maine better to flush in the winter when your vinegar solution will be very cold indeed. Useful to do a final flush with antifreeze.

[BQUICK]

What were the fittings on the T stat covers you used?

1/4 pipe thread with 3/8 hose nipples

[DannyMart]

Seawater contains a near saturated solution of Calcium Hydroxide and is slightly alkaline. Calcium Hydroxide demonstrates inverse solubility eg it is only half as soluble at 70 degrees Celsius as it is at 20 degrees Celsius and thus precipitates out in a warmed up outboard. Calcium Hydroxide solution is corrosive to Aluminium so the crud in the cooling passages is mostly Calcium Hydroxide with some contribution from your engine. Lowering the PH increases the solubility but a strong acid will attack Aluminium also so flushing with a weak acid such as vinegar makes sense but a cold solution should be used. In Maine better to flush in the winter when your vinegar solution will be very cold indeed. Useful to do a final flush with antifreeze.

Good catch on the temperature issue. I assumed the warmer the solution, the fast the reaction, but as you pointed out, this is not true for Calcium Hydroxide in water. What about moderate strength acids?

I may have to do a test of how fast Hammerhead descale will dissolve a mass of Calcium Hydroxide at room temperature and about 110° F. The 115 V pump I will use has a max fluid temp rating of 120° F.

[zenoahphobic]

Good catch on the temperature issue. I assumed the warmer the solution, the fast the reaction, but as you pointed out, not is nor true for Calcium Hydroxide in water. What about moderate strength acids?

I may have to do a test of how fast Hammerhead descale will dissolve a mass of Calcium Hydroxide at room temperature and about 110° F. The 115 V pump I will use has a max fluid temp rating of 120° F.

You will find the warmer the quicker!

But:
Good point to test. We need a good solution to this problem (pun intended). Everyday consumer products tend to be too weak, however it is a fine balance between effectiveness and doing more harm than good (the dissolving of good aluminium ).

On the question of temperature, there is a difference between solubility and chemical reaction. We need to remove a solid (calcium mixture), to do that we need to ionise it into the water solution to react with another ionised chemical. Chemical reactions work quicker the warmer the solution. However too strong a concentration will slow the process because there is not enough water for the ions to go into, temperature helps but does not limit the capacity to hold these ions.

So one wishes a definitive process, that is: the chemical(s) to be used, the concentration, the temperature, and the time allowed for the solution to be in contact with everything (the crud, aluminium , paint, plastics and rubber etc. And be safe to handle.

[cleddau1]

The chemical reaction involved is:
MolecularEquation : Ca(OH)2 + 2 CH3COOH → 2 H2O + Ca(CH3COO)2
The Calcium Acetate formed is more soluble than Calcium Hydroxide but for this reaction to occur the latter has to dissolve hence the advantage of low pH and low temperature.
A more concentrated vinegar solution would help. Calcium Acetate is also soluble in alcohol so adding leftover Xmas booze (however unlikely) to the mix should be considered.
If you add sufficient alcohol to a concentrated Calcium Acetate solution a gel is produced that can be shaped into a snowball. This snowball is inflammable. Playing flaming snowballs would be fun.........

[zenoahphobic]

DannyMart have you done your test yet? What is the active ingredient in Hammerhead Descaler, so we actually know what the actual chemical reaction is? ( I'm a bit distracted, why would you descale a hammerhead , they don't have scales!)
Cleddau has me thinking. Forget the vinegar, just put in your stale wine from Xmas, oxidised ethanol is acetic acid (vinegar is made from wine).
Organic chemistry was not my strongest suit.

[DannyMart]

DannyMart have you done your test yet? What is the active ingredient in Hammerhead Descaler, so we actually know what the actual chemical reaction is? ( I'm a bit distracted, why would you descale a hammerhead , they don't have scales!)
Cleddau has me thinking. Forget the vinegar, just put in your stale wine from Xmas, oxidised ethanol is acetic acid (vinegar is made from wine).
Organic chemistry was not my strongest suit.

I'm out of town and won't be at the house with the motors for a week.

Rydlyme is another popular descaler, but the base is HCL and their fine print warns about the solution etching AL.

Hammerhead specifically states that it is safe to use on AL, hence my choice. My engines haven't been overheating, but starboard engine is running little hot at cruise, so I am being proactive. The engine running warm takes 7:30 to fill a bucket to 2.5 gallons with the telltale stream when connected to the garden hose. The cooler engine fills 2.5 gal in 5:02.

I did a 3 hours flush with 8 gallons of undiluted 5% vinegar a few weeks ago on the warm motor and noticed no change in the time to fill 2.5 gallons. The telltlae on the hose with the engine running was marginally greater. It may not mean anything, but there might be minor obstructions in the cooling passages between the hose attachment and telltale outlet.

Hammerhead does not specify their acid base but states that it does not contain hydrochloric or phosphoric acid.
http://www.tadiesels.com/descaler/TA...e-Descaler.pdf
The pH of Hammerhead is about 2.0.


My 200 HPDI are 12 years old and only have about 700 hours. I want to keep them running for many more years.

[zenoahphobic]

Yes I've done more reading, there are plenty of discussions on other forums. Hammerhead don't disclose their ingredients. But I suspect they target marine organism caused scaling, that I don't think relevant inside outboard engines, as they spend no time idle with seawater for anything to grow.
They also don't list aluminium with all the other metals but make a special note AL 1100. Looking to find what that is.
Always sceptical about glowing advertising. So good I can give it to my great grandma to clean her pipes out it would seem.

[DannyMart]

AL 1100 is specifically mentioned for use in heat exchanger units.

https://www.cometmetals.com/metal-de...num&pg_id=5141

Engine manufacturers probably use proprietary alloys. I've ordered a coupe of thermostat covers so I can add hose bibs to the old covers for flushing. I could pre weight the new covers on precisions scales at work and get some photomicrographs to look for etching after a soak in Hammerhead.