Core plug, welch plug (welsh plug) removal

[headdownarseup]

well, what i used to do was have a scrape and poke with stiff wire which would release quite a lot of rust to begin with.
BUT, i was then finding that after i had cleaned out the block, 6 -12 months later the rust would be back again (not as bad as the first time)
so i thought that using the acid would dissolve the softer material first and get back to solid cast metal. (which it does brilliantly) and finish with caustic soda and plenty of water . i usually then soak the waterways in either wd40 or diesel for 1 week.

with century blocks, its much easier to see nearly all the waterways (except the blind one on the back of the exhaust port, that's where acid comes in handy.the acid will only dissolve the rust and not the metal) it all depends on how long you leave the acid to work. i dont leave it for more than 48 hours before checking everything is ok.normally i will soak in acid for 24 hours at a time then flush with water every time before i try again . if there is no more rust coming out or the acid/water comes out clear, then i swap over to caustic. soak in caustic for 24 hours and flush with water. then i "preserve" with wd40 or diesel.
works every time. even when i use the motor for a season it still pumps water like its brand new!

[phil]

I hear Coca Cola works well as the acid as well, contains some phosphoric acid I guess. Have used Naval Jelly, got in it in the U.S., on exterior rust it works very well and acts as a primer for paint later. It is mainly a gel form of phosphoric acid it seems.
Have also used molasses and water mixed, works very well but takes weeks, rather than hours, thus usually needing topping up occasionally. Some of the stationary engine bunch routinely degrease, then soak the whole stripped motor in molasses water mixture for weeks or months.

[headdownarseup]

coca cola also works at freeing up a seized piston.
it does take a few weeks but the longer you leave it the better it works.
there are a few acids that will do a sterling job of rust removal provided you are sensible with its use.
experimentation with caution on these seagull blocks. it all depends on how thick the casting metal is to begin with.

[haventaclue]

I have tried the coke method with limited success. These days I use a 5l bucket,three or four table spoons of bread soda,a12v battery,a s/s fork but any piece of s/s will do.Tie a piece of heavy copper wire to rusty component,connect to neg. Tie another piece of wire to s/s fork connect to pos side.Leave overnight.And if afraid will run down,I hook up to charger on trickle charge.In the morning,power hose or blow through with air.Wear safety glasses!!!You will see bubbles rising from the rusty piece.Did that with the head of my "new" seagull.Came up well.

[Stelios_Rjk]

ATTENTION PLEASE

Rust removal with electrolysis, using a sacrificial anode made of stainless steel (s/s) emits in the solution Hexavalent Chromium which is carcinogen.
Using plain steel is safe or I haven't heard anything bad about it. It only melts after some use.

Coke according to my experience/experiments works best in freeing seized bearings and maybe pistons. I believe it's highly penetrating maybe because of the carbon dioxide and because of the phosphoric acid it kills the rust and frees parts. But it doesn't have so much acid to kill the rust in a water jacket. Inside there, there is a lot of rust so something really stronger may be more suitable. Never muriatic acid (just in case anyone is tempted). Strong phosphoric acid would do. And after the acid an alkaline bath is suggested to neutralize the water jacket.

[phil]

It is always most important to get the rusty metal thoroughly degreased, the rusty water jackets will likely be a bigger challenge because of the semi porous rust that can be be more or less saturated with oils or one kind or another often by intent but also just through regular use.
That suggests using a hot solution of sodium hydroxide or lye, or a thin bodied hydrocarbon like acetone, lacquer thinner etc. All of them seem to have some hazard attached.

[headdownarseup]

all very good suggestions gentlemen.

however as this post was originally to do with the round block 102 models which are fairly inaccessible at best compared to the square block 40 and 100 blocks, all of these methods will work with varying degrees of success. as we are slowly realising, the very old seagull 102 roundblock motors with the removeable core plug/welch plug offer much more access for internal cleaning.
compared to the 40 and 100 blocks, once you have removed the cylinder head from the block, the water jackets are considerably easier to clean with whatever method you choose.
from my own experimenting, acid (from car batteries, just because i have plenty of dead ones to choose from at work) or caustic soda have done a very good job on the motors that i.ve overhauled.
all things being equal, a lot depends on how bad the corrosion/rust is to start with and what exactly is seized/blocked within the engine.
seized pistons respond fairly well in my experience from intense heat from oxy-acetylene torch and gentle pressure from a hydraulic press (only do this if you're confident that there will be no damage to the piston crown) or leave to soak in coca cola for weeks on end. i've done this a couple of times before with reasonable success, the longer you leave it the better it works. (patience wins through)

other members have removed the later "pressed in" type of core plug to gain a bit more access to the water jacket. again using the probing/scraping method which will work quite well until you need to get to the "tight area" around the spark plug hole which would be the "hot" end of the cylinder.
the trouble is it really is very narrow in the jacket at this end of the cylinder. caustic will work here, so will acid.
as STELIOS had asked earlier as to what the chemistry was, i dont know? all i know is that it works for me.

bottom line is, as long as the cylinder has sufficient water flow through the block to keep things cool, then thats all that matters.
seagulls are not a high performance motor compared to other outboard engines. max rpm's for a seagull are circa 3500 so temperatures in the waterjacket (depending on through flow) are generally quite low compared to a motor turning at say 10-15000 rpm with higher compression and temps.
seagulls are more "tractor" than sports car.
refer to the pictures below and this should help to show the "tight area" as i call it around the spark plug hole and the entire water jacket for one side of the block.
this block does have the removeable plugs either side but it does show you just how bad some of the corrosion can be in places.
this block is beyond any help other than for reference purposes but all the 102 blocks (except the SD/SDP and marston 102 blocks)) will be the same as this.

i hope all this helps in some way to you all?

[Stelios_Rjk]

That looks like a chocolate easter egg attacked by a little fellow!
Very informative, I had imagined those things about the "tight areas" now I can also see them, thanks!