outboard descaling

[UNIQUE_NAME]

i have a yam 9.9 2 stroke that the mechanic says has salt scaling in the block and head. it has new water pump, pisses water at idle and low speed, you can see a crust on the external head gasket flange and the head is that color aluminum gets when it has overheated. the engine is at a point if you run it at anything more than idle load it will stop pissing and overheat. he says since we can see the crust and evidence of overheating, the block surface is probably already pitted and if you pull the head off they won't seal properly when re-assembling and he is not aware of any way to flush it out. any ideas on how i might try and save it or do i have a manmade reef in the making?

jim

 

[Boatsb]

Vinegar will take some scale off. Stronger acids too but the aluminum is the question. If you think it's just scale try to clean it out with a descaler. Even CLR may clean it out. If it eats the block you will end up with a reef extension but what do you have to lose?

 

[sgharford]

I have a mercury 3.3 HP two stroke I recently de-scaled by removing head. She had same symptoms, barely pissed at idle and stopped peeing altogether at anything above idle. It's really easy to remove head on two stroke and dig out passages with a small screw driver. Probably 98% of cooling cavity was blocked by salt. She's as good as new now and was only $12 for head gasket. I can't imagine any solvent getting all that crap out, was at least 1.5 cups of what looked like melted salt packed in my little engine. Sounds like you have little to lose by pulling the head anyway at this point, but interested in seeing if somebody knows a liquid cure without dismantling engine.

 

[krush]

see the heat exchanger cleaning thread. Same idea

 

[REBrueckner]

How old is the outboard??

I seem to recall hearing some (small??) Yamahas were prone to this....still don't understand why unless it's the aluminum composition more than salt causing the build up....or could it be cooling passages are too small??

If it IS just salt, then running the outboard in a container of fresh water should dissolve it.....maybe add some vinegar....but I suspect running in plain water won't be the cure....

I sold a 1989 and a 1999 Merc (9.9, 15 HP) with my Hatt several mos ago and never had any cooling problems....they were always used in salt water and I each for 11 years...

 

[sgharford]

I put mine in a garbage can filled with regular water and let her run for about 1/2 hour. Didn't do a thing. I used this little engine pretty often for about 10 years with no problems up until the 10th year. Winterization every year included running it in garbage can of fresh water. I think once the salty/scale layer starts, additional salt accumulates very quickly.

 

[UNIQUE_NAME]

update,


removed the head, snapped 4 head bolts (none with antisieze) during the surgury. head was welded to the block with saltcrust so during the removal process another manmade reef was created. oh well....