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NEED HELP *Merc cooling system

Old 02-10-2019, 05:48 PM
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Default NEED HELP *Merc cooling system

Hey there,

I have a mercury 150 2 stroke and I cant get it to pee right. The tell tale stream has volume but it pulsates and I have changed the whole water pump assembly including the base, Ive also changed the thermostats ( which i gutted down the rd), and poppet. before all this the stream was weak and pulsating creating an overheat but now i have a much better stream and no overheat horn, however its pulsating and if i sit at idle for a little while every so often i see some steam, i cant keep my hand under the water stream.

can anyone please help me figure this out. Do I have a blown head gasket?

Thanks in advance!
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Old 02-10-2019, 07:07 PM
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I would wonder about a leaking head gasket.
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Old 02-10-2019, 07:31 PM
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Originally Posted by captbone View Post
I would wonder about a leaking head gasket.
how would i know if thats it? it crossed my mind
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Old 02-10-2019, 08:46 PM
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You can do a leakdown test or pull the heads.
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Old 02-10-2019, 09:33 PM
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pull the heads and replace the gaskets , check for corrosion into the combustion chamber,
while your replacing gaskets , do the exhaust cover one as well., that way you can see if there is excessive corrosion in that area.
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Old 02-11-2019, 03:16 AM
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Originally Posted by 1breakinit View Post
pull the heads and replace the gaskets , check for corrosion into the combustion chamber,
while your replacing gaskets , do the exhaust cover one as well., that way you can see if there is excessive corrosion in that area.
you think this may be my issue? Does that mean that I may be getting some water in at least one of the cylinders?
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Old 02-11-2019, 03:17 AM
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Originally Posted by 1breakinit View Post
pull the heads and replace the gaskets , check for corrosion into the combustion chamber,
while your replacing gaskets , do the exhaust cover one as well., that way you can see if there is excessive corrosion in that area.

is this the gasket that may be leaking? And which other should be replaced as well?
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Old 02-11-2019, 05:48 AM
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Try cleaning the pee hole with a piece of wire, on my Merc 60 debris will build up in it blocking the flow, keep a piece of s/s wire in the console just for this.
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Old 02-11-2019, 05:57 AM
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Originally Posted by PF-88 View Post
Try cleaning the pee hole with a piece of wire, on my Merc 60 debris will build up in it blocking the flow, keep a piece of s/s wire in the console just for this.
Iíve tried this and itís clean. I know because when I run water with the hose connected to the rinse plug it pees just fine. I wish that was my problem haha
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Old 02-11-2019, 06:24 AM
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Originally Posted by Thebusdriver View Post


Iíve tried this and itís clean. I know because when I run water with the hose connected to the rinse plug it pees just fine. I wish that was my problem haha
So what changes between flushing with the hose and running the engine? positive water intake pressure? might give you some insight to the problem.
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Old 02-11-2019, 06:29 AM
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Originally Posted by Thebusdriver View Post
Hey there,

I have a mercury 150 2 stroke and I cant get it to pee right. The tell tale stream has volume but it pulsates and I have changed the whole water pump assembly including the base, Ive also changed the thermostats ( which i gutted down the rd), and poppet. before all this the stream was weak and pulsating creating an overheat but now i have a much better stream and no overheat horn, however its pulsating and if i sit at idle for a little while every so often i see some steam, i cant keep my hand under the water stream.

can anyone please help me figure this out.

Thanks in advance!
Run Salt away into the head and leave there 24 hours. Then run Salt Away again about a half dozen times. This is a cheap, easy solution just for the heck of it.
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Old 02-11-2019, 07:12 AM
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Originally Posted by PF-88 View Post
So what changes between flushing with the hose and running the engine? positive water intake pressure? might give you some insight to the problem.
im not ruling it out but the LU got cleaned really well when I did the pump and all seals... I even had a mechanic check my work and go back and replaced my base plate and new impeller to make sure. The flow got better with new impeller gutted thermostats and new poppet but still pulsating at the tell tale. Any other place I should look in the intake portion of things
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Old 02-11-2019, 07:13 AM
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Originally Posted by SWF Pontoon Angler View Post
Run Salt away into the head and leave there 24 hours. Then run Salt Away again about a half dozen times. This is a cheap, easy solution just for the heck of it.
i will try this. Thanks!

Someone said some vinager ages would work too? Ever heard of that
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Old 02-11-2019, 08:04 AM
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Use a jar and collect the water coming out of the pisser. Look for exhaust/smoke in the jar mixed with the water. If you leaking past the cylinder wall and exhaust is creating the pulses in the pisser then you should see exhaust smoke coming out of the pisser. No exhaust should be coming out the tell-tale.
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Old 02-11-2019, 08:25 AM
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Originally Posted by Thebusdriver View Post


i will try this. Thanks!

Someone said some vinager ages would work too? Ever heard of that
Don't mess with other stuff, Salt Away does what it was made for.
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Old 02-11-2019, 08:55 PM
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Originally Posted by captbone View Post
Use a jar and collect the water coming out of the pisser. Look for exhaust/smoke in the jar mixed with the water. If you leaking past the cylinder wall and exhaust is creating the pulses in the pisser then you should see exhaust smoke coming out of the pisser. No exhaust should be coming out the tell-tale.

are you being serious about the jar??
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Old 02-12-2019, 05:40 AM
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Lol. Yes.

There should be no exhaust coming out of the tell-tale.
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Old 02-12-2019, 06:52 AM
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you can sometimes smell the exhaust fumes in the steam coming out the pisser when a gasket leak is real bad..
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Old 02-12-2019, 07:15 AM
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Does it overheat?

My motor did that at idle but once I brought up the revs, it became a solid stream. All my mercs have had a pee stream that was too hot to keep your hand under. Never overheated. But even 160 degrees is too hot to keep your hand under
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Old 02-12-2019, 07:33 AM
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Originally Posted by captbone View Post
Lol. Yes.

There should be no exhaust coming out of the tell-tale.
lol ok just wanna make sure. I donít know too much about outboards. So if thereís exhaust coming out the tell tale with the water I have a head gasket leak?
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