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1970 Merc 800 water blocked

S

sebagojoe

New member
After removing the lower unit

After removing the lower unit I put the garden hose on the water tube and no water exits the motor.
I have searched the forum and can not trace it. I also have the factory manual but it does not break down the PATH that the water takes after it leaves the water pump. This unit does not come with a thermostat from what I know.
So where do I go from here?
Thanks.
 
"Johnny, the water travels up

"Johnny, the water travels up the water tube to the base of the powerhead (roughly the base directly behind the carbs).

It then flows along a channel which runs along the base of the powerhead then up and around the cylinders and exits down the leg...

Possible "clog" points are at the top of the water tube where it connects to the powerhead or a build-up in the channels themself (salt if run in salt water or minerals/sand/mud etc if run in dirty or polluted water).

Unfortunately, the only way to check the top of the water tube is pull the power head.

Build-up in the heads can usually be dissolved with various commercial products such as "CLR" or a simple solution of 1:1 white vinegar and water..."
 
"Hmmm, more than likely I am p

"Hmmm, more than likely I am pulling the head, bummer. I will first bull the water tube and make some sort of a grabber or pick and poke in there and also I was thinking of forcing water in both directions back and forth. I like the CLR idea too. OK, two questions: if this had a thermostat where the heck would it be located? I have searched tons of exploded views on the web. The reason I ask is that although the ser#2786656 shows it as a 1970, the mid section has the speedo pickup. Also, if it is in fact blocked, where was the water going? Was it killing the water pump?"
 
"don't forget the easy sol

"don't forget the easy solution, muddobber in the pee tube. Can be cleaned out with some weed whacker string and effort"
 
"DON'T try to remove the w

"DON'T try to remove the water jacket (spark plug) cover, or the exhaust plate unless all other attempts have failed. Trust me on this! The bolts love to break off, and there's a zillion of them.

I'd pull the power head and see what's happening. Blow compressed air in where the water goes, poke with a wire--anything but removing those covers!

Jeff"
 
"Thanks Jeff, I git it, start

"Thanks Jeff, I git it, start with the small possible fixes, then the powerhead - covers as a last resort. I appreciate the advice. Funny thing but, I would swear that the water jacket at the spark plugs looks brandy new. And I see other indications that someone had ripped her open at one time.
Thanks."
 
"Hi Johnny,
When you

"Hi Johnny,
When you do pull the powerhead ,invest in a lot of cobalt bits,a gallon of milling oil,twenty yards of patience and the name of a good divorce lawyer
biggrin.gif
. Just been there,no divorce though,very understanding wife.
sun.gif

Push as much air in as possible,and there is no thermostat.There is a brass nut in the middle of the cover between #2 and #3 plugs,unscrew this as you pump water in and see if it is getting this far.If it is, the blockage is more than likely in the pee tube.I think it's more than likely there any way."
 
"Noel is speaking about drilli

"Noel is speaking about drilling out all those water jacket cover bolts.

Obviously, the man has been there!

Jeff"
 
"When we work on merc's he

"When we work on merc's here in Aus its with a oxy torch in one hand and a spanner in the other...breaking bolts off makes me
sad.gif
"
 
"Me too! On a triple I've

"Me too! On a triple I've been working on, I went through a fistful of drills and several helicoils on the exhaust plate alone.

Jeff"
 
I have got a 1977 850 mercury

I have got a 1977 850 mercury . It idles fine but when I take off the motor loads up and the boat won't plane out . I bought a new prop but this didn't help . my friend told me the spark advance may need adjusting. I haven't got a clue how to do that . i found a screw for it . please help.
 
"Loads up - or boggs down? If

"Loads up - or boggs down? If a screw dropped I might try spraying carb clean arount the carbs. Use the straw and be careful where you shoot it. If it surges at a gived spot, the crew might have come out. Or maybe poor output from the fuel pumps. If it were me I would start there because they are easy and fast to do. You could also have a ground issue which only shows up at higher rpms"
 
"update: First I need to say,

"update: First I need to say, if I knew the path that the water took I might have figured this out faster.
OK, I did not know that the water exited the prop so I was looking for water to come out the two rectangular hosed al the top of the mid housing (like an OMC without through the prop). So after buttoning the lower up I figured it out. Fished trimmer line in the blocked telltale hose, saw it was blocked, disconnected it and cleaned it out some more and water started exiting the telltale. This thing was probably pumping fine but I was looking for that water exiting in volume from the back.
So it is all set. Thanks to all for the help."
 
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