Thermostat Corrosion issue

Bought this 1993 Force 50hp a few months ago.
It runs awesome and has good compression.

It has been sitting a few months and got it out today to get
ready for crappie season. Cleaned the carb, it is spotless.
New fuel pump and carb kit a few months ago.
Got a good pint of water out of the 6 gallons of old ethanol gas.
Have good fresh non-ethanol and SeaFoam to replace that junk.
I checked the water pump and impeller looks good. But will get a new one anyway.

Just for grins, I pulled the T-Stat cover to check it and Low and Behold - - - -
there is NO thermostat !!! Looks like it may have been run in salt .....
I have very little history on this motor.


my question is - - - - is there something I can run through the water system
to clean this mess up ?? I have never seen a water system this bad - never.
I just don't want to pull the head and water jackets off.
Am ordering a new T-Stat and Impeller Kit today . . . . .

Thanks !!







.

Pappy is the final authority, but I have 'rescued' more than one salty OB by turning it upside down and filling the water passages full of white vinegar to dissolve the encrusted salt. Some run in barrel of Salt-Away, but that's an expensive proposition.

Would love to hear Pappy's advice!

Thanks Dale. But removing this beast from the transom is not possible.
I am very limited to the help in my neighborhood now that all the
young men are in college or working.

My thought during lunch was to be a little more aggressive.
In a 35 gallon plastic trash can, fill it with water to cover the
water intake and add maybe a quart or so of muriatic or
sulfuric acid pool cleaner. Run the motor for 15-20 minutes on idle,
rinse well with clean water for 15-20 minutes . . . .
then, mix a baking soda solution to neutralize any residual acid, 15-20 minutes.
then a final rinse of clean water for 20-30 minutes.
install the new thermostat then go boating for an hour or so.

anyone see any problems with that procedure ??



.

I've only got limited experience using muriatic acid, but I'd be scared to run any form or dilution ratio of that stuff in my motor without hearing it from some professionals first. As fast as that stuff eats some things (including metals) it might pop a hole in something that already has thin walls due to corrosion.

Johnny -

You may be there for a while trying to neutralize the muriatic acid residue with baking soda. Acid when the engine is hot will be 10X more aggressive than when cold. Can also eat gaskets.

You can get a pH meter for $10 on ebay to monitor the acid bath pH to keep it above 4 or so... and verify you have increased the pH to 7 or so when washed out. If you're taking it out for a run right away [while still wet inside] - that should clean it out.

okay, disregarding any warnings, I made the decision to acid wash the motor.
in a 35 gallon trash can filled with water, I put in one quart of muriatic acid. Which would be a 140:1 ratio.
Ran the motor for about 20 minutes. It sat for about 10 minutes to siphon out the water.
Filled with fresh water, ran for 10 minutes. Siphoned it all out, added fresh water and 5 boxes
of baking soda. Ran for 20 minutes. Drained water, filled with fresh, ran for another 30 minutes.
Removed thermostat cover just to see how much water is circulating as I have never done that before.
Pretty interesting to see. Ran for only a couple of minutes with the cover off.

Replaced cover and ran for another 20 minutes. In all the clean flushes, the water hose is open full
to provide a fresh input as I do not have muffs that will fit this motor.
Note: Force outboards do not have a pee stream. Only a fluttering of water with exhaust gasses.
at first, the spray only went about 3 feet from the motor..... after the acid wash, the spray went SIX FEET from the motor.
The motor block and head was only warm to the touch, not hot.
The exhaust water was the same, only warm, not hot.
So there was not a "heat issue" in this procedure.


So, do I recommend this procedure ? probably not - but, if you do it, do so at your own discretion and risk.

I now have the new thermostat, grommet and impeller . . . . good to go !!!






Note: I have been messing around with sulfuric, hydrofluoric, hydrocloric and muriatic acids since the
mid '70s. So they are in no way new to me. This is just my first outboard motor flush.
On a second thought, I wonder if the automotive radiator flush would do the same ????

READ, UNDERSTAND AND FOLLOW ALL WARNINGS AND INSTRUCTIONS
ON THE LABEL OF ANY HAZARDOUS MATERIALS YOU WORK WITH !!!






.

Wow, I'm impressed! It looks like it worked great! Took stones to do so too 8)

Wow!!! Good deal!!!!! Looks great!!!!