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  1. #1
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    1988 Mariner Mag2 150hp cooling system

    Serial# 0B381964. This motor has never had water exit the pee hole since I have had it. I've had the impeller changed twice, blown out the system with air, flushed it with water, replaced Tstats, etc...still nothing. I have pulled all cooling hoses, and have good water circulation throughout. I've ran it in a tub, muffs, and in the lake. Still, no water pees out. Only thing I haven't done is checked the poppet valve. I am about to do some other work (new stator and cdi boxes), and sure would like to figure the whole pee hole thing out before I put it back on the water. Somebody tell me what I am missing, please.

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    #2
    If the poppet is stuck open it may not build enough pressure to send water tot the pee hole. Do you have a water pressure gauge? If so what is your idle water pressure?
    Mercury 2002 200hp Carbed Saltwater
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    #3
    My gauge had been reading a little low. Never really got above 12psi, but I found that issue when I diaged the stator. I had a kink in in my line right at the 90* brass fitting. I haven't been able to run it since I found that.

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    #4
    kink will do it
    .................................................. ...the scariest thing in life is the unknown ...................................

  5. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #5
    As you're probably aware, telltale comes FROM the thermostats. There will be little or no telltale present until, or unless the thermostats are OPEN.

    Definitely go ahead and do the poppet valve... and if you have not already, replace the complete water pump assembly (including all three (3) gaskets). Consider water pump a "once per year" item, or sooner if water pressure/cooling system problems develop.


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
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    #6
    Here is what I have right now. Water coming from starbord exhaust, some water seeping from #1 & 3 plugs, and a tiny amount of steam coming from the pee hole.

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    #7
    Took off the poppet valve and housing, and have good water coming from there.

  8. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #8
    Quote Originally Posted by Kdk3460 View Post
    Took off the poppet valve and housing, and have good water coming from there.
    You should have. Need to check each component, make sure none of the gaskets are "hooching" into passages, make sure poppet moves smooth as butter in and out of the seat/grommet, and make sure the spring/valve/diaphragm are all in good condition. If in doubt- change it out.

    Might want to clarify what you mean my "starboard exhaust" since the exhaust combines in the midsection at the bottom of the tuner.

    Water seeping from #1 and #3 plugs is definitely a problem... hopefully you have the earlier water-jacket style heads and it's simply that outer gasket that's leaking.


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
    Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor

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    #9
    Here is a pic of the water coming from the exhaust, and one of the spark plug water. I have looked all the poppet parts, and water pump assembly to order. Going to get all that done anyway.IMG_1053.PNGIMG_1054.PNG

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    #10
    The 2 piece cylinder head shown in your 2nd picture appears to be the type used on the 1st Gen V6 blocks. I think this was somewhere between 1979 - 1983. Has your powerhead ever been changed out?

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    #11
    Quote Originally Posted by OnTRAK View Post
    The 2 piece cylinder head shown in your 2nd picture appears to be the type used on the 1st Gen V6 blocks. I think this was somewhere between 1979 - 1983. Has your powerhead ever been changed out?
    I have no idea about that. The parts that I have bought for it so far was bought by the serial number on the mount plate, and have worked. I put a stator and 2 cdi bixes on it today off of that serial#.

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    #12
    Quote Originally Posted by OnTRAK View Post
    The 2 piece cylinder head shown in your 2nd picture appears to be the type used on the 1st Gen V6 blocks. I think this was somewhere between 1979 - 1983. Has your powerhead ever been changed out?
    +100 early v6 block
    .................................................. ...the scariest thing in life is the unknown ...................................

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    #13
    There should be a welch plug (looks like a freeze plug) on top of the block behind the fly wheel. It should have the serial number for the power head stamped on it. Check to see if it matches the serial # you're using.
    Last edited by OnTRAK; 01-04-2021 at 09:17 AM.

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    #14
    Quote Originally Posted by OnTRAK View Post
    The 2 piece cylinder head shown in your 2nd picture appears to be the type used on the 1st Gen V6 blocks. I think this was somewhere between 1979 - 1983. Has your powerhead ever been changed out?
    +100 early v6 block also very early mid section see where hose connects to adapter plate poppet has to open before water will exit hose, put it back together fix that temp sender on stbd head for overheat horn operation please, that mid section is a 77-79 vintage not 88 promise been there seen that the early mids used exhaust dump as idicator for w/p
    .................................................. ...the scariest thing in life is the unknown ...................................

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    #15
    Quote Originally Posted by JOE54 View Post
    +100 early v6 block also very early mid section see where hose connects to adapter plate poppet has to open before water will exit hose, put it back together fix that temp sender on stbd head for overheat horn operation please, that mid section is a 77-79 vintage not 88 promise been there seen that the early mids used exhaust dump as idicator for w/p
    I've noticed that wire several times. Wasn't sure what it was. I don't even know if this rig has a warning buzzer on it. So if all of this is a potpourri of different years, then the water exiting the exhaust will sub for the pee hole? Once I put the poppet valve back together, I should be ready to go?

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    #16
    needs warnning horn for sure or some kind of indicator
    .................................................. ...the scariest thing in life is the unknown ...................................