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  1. #1
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    Merc 250xs - Water Pressure and Temp Question.

    Merc 250xs
    2005
    Ser# 1E000996
    Merc Monitor Series 1

    New water pump and service about 3 months ago. I was getting 15-20 psi. Recently changed my jackplate. Same setback. First trip out I was too high. I knew it, but didn’t have tools to lower. Ran 1/2 speed 3-4 times about a mile each run to some close fishing spots. Water pressure was only about 8-10 but at only 50/60% from WOT. Reset motor at correct height and the same as it has been for long time. Today (next trip) I could only get 12.5-13 psi at WOT instead of the 15-20 in the past. Engine temp would get 130-135 and stay in that range. No idea what my water temp used to be. Only know today because I was watching because of water psi. Pee stream looks normal. Idle psi is 3.5 which I think is normal. No alarms or anything and ran great.

    Is the 12.5-13 psi a concern?
    Is temps in 130’s normal?
    What could/would cause by water pressure to drop by 5 basically from 1 trip to the next?

    My concern was an air gap from that 1 trip running too high or could that 1 trip have damaged the rubber on impeller without ever over heating the engine? Or something else like poppit?

  2. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #2
    The 12.5-13 @ WOT is the only real concern. Really need a minimum of 15 (and prefer to see 18+ for safe measure in turns).

    Either there is a pump problem (impeller/gaskets/top seal)

    -or-

    Engine is still too high (by about 1/4"

    -or-

    Both of the above.


    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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  3. Member
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    #3
    Thanks. Engine is definitely not too high currently. I am actually 1/8" lower than I have been running for over a year. I have previously been able to run at least 1/4" higher without any water pressure issues. I will have to bring to a shop and have them look at the internals.

  4. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #4
    What is your current Prop-to-Pad, What jackplate, and which boat/hull?

    Perhaps I misunderstood you from Post# 1, but it sure sounded like you just installed a new jackplate, and it was too high the first time out.


    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

  5. Member
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    #5
    Quote Originally Posted by EuropeanAM View Post
    What is your current Prop-to-Pad, What jackplate, and which boat/hull?

    Perhaps I misunderstood you from Post# 1, but it sure sounded like you just installed a new jackplate, and it was too high the first time out.
    1/2 right

    Bullet 21XDC
    14" JP
    Gen 1 TM
    Very common set up is 1/2-3/4" below pad depending on load. 3/4" most common.

    Currently set at 3/4" below pad, been running at 5/8" for 11/12 months. I did just change JP and did hit the lake without checking and I was at 1/4" below pad. Moved it down 2 notches to 3/4". At 1/4"my water pressure was 8-10. Probably ran about 2 minutes before I noticed lower water pressure. Fished and ran it about 4000 Rpms back to ramp. Stopped 1/2 way and fished to cut drive time down. Lowered it 1/2" and last trip was the recorded 12.5-13. I guess there's a chance that I might've damaged pump/impeller slightly that initial trip without actually over heating. It's 4 months old roughly.

  6. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #6
    Thanks for clarifying. Be sure to report back after you get a chance to check the pump (and if no problems, the low water inlets and PTP).

    Curious one, for sure.


    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

  7. Member
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    #7
    Partial Update

    Had my local shop change water pump kit today. Just got home and at idle, water pressure on smartcraft has increased from 3.5 to 4.6. He said the old one didn't look or come out as if it was only 4 months old. I know I had other shady issues at the shop that did the last PM. They were the closest dealer for brand of boat I bought so I tried to start a relationship there, but lots of trust issues that remind me of 1970's used car lot. Hopefully with the seemingly better pressure at idle and possibly a NEW water pump kit, my issue will be resolved. It'll be Sunday or Monday afternoon before I can take it to the lake and find out for sure.

  8. Member
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    #8
    UPDATE

    Ran the boat today. 15.5 psi at WOT (6000). 13 psi at about 5000-5200 rpms. At idle - 4.5.
    I'm pretty sure I used to get 18-20, but maybe not.
    The pee stream is very strong even at WOT.
    Idle temp -127
    Run temp was 133-135. I never saw it go over 135.

    About what temp range will usually set the alarm off?
    Last edited by barbarian; 01-08-2020 at 10:59 AM.

  9. Member lpugh's Avatar
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    #9
    Bet your still a little to high with the motor. I would try dropping it a little to verify
    Thank You Leon Pugh

  10. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #10
    Quote Originally Posted by lpugh View Post
    Bet your still a little to high with the motor. I would try dropping it a little to verify
    That is my thought as well.


    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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    #11
    If you drop the motor and the water pressure INCREASES, then you know that the lower unit is sucking air.



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    #12
    Wide open throttle with 135 as the temp in the winter sounds way too high. My optimax when running in the winter with water temps in the low 50's will hit 106 to 114 max. In the heat of summer I run from 115 to 125 max ( a very hot day with very warm lake temps ).

    Your motor is likely too high. Drop a 1/4" at a time until you hit around 20 PSI and so your temp goes down. it may only take 1/4 to do this. I get 20PSI+ but most of the time I am running close to 25psi but I think at 20 you are in a good safe place and likely optimum height. This is based on my on the water experience and please confirm with Don as he would know the optimal PSI and temp numbers better.

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    #13
    I truly appreciate the opinions, but guarantee my motor is not too high. 100’s of people running exact setup at 1/2-3/4” and getting plenty of psi. I ran 1/8-1/4” higher over the past 12 months - same boat and motor.

    I’m just refusing to buy into the theory of motor height. Is there anything else on the motor that can affect water pressure?

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    #14
    checked your poppet valve seat for debri and operation ?????
    .................................................. ...the scariest thing in life is the unknown ...................................

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    #15
    Quote Originally Posted by JOE54 View Post
    checked your poppet valve seat for debri and operation ?????
    No I haven’t, but I will if it has any chance of being part of the issue.

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    #16
    How about checking to see if you are getting a correct reading at your guage. Maybe something got in the water line from your motor to your gauge. This line needs to be removed when you do a water pump R&R. Maybe when put back, something got in the line.

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    #17
    it is part of the cooling system every thing must be checked if you are having a problem,the gasket that seals shift shaft cover also check it all, you could have base or adapter plate gasket leaking, gotta be thorough in your search for the problem eliminate the likely to the unlikey
    .................................................. ...the scariest thing in life is the unknown ...................................

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    #18
    Quote Originally Posted by tomloans View Post
    How about checking to see if you are getting a correct reading at your guage. Maybe something got in the water line from your motor to your gauge. This line needs to be removed when you do a water pump R&R. Maybe when put back, something got in the line.
    everything
    .................................................. ...the scariest thing in life is the unknown ...................................

  19. Member
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    #19
    Quote Originally Posted by tomloans View Post
    How about checking to see if you are getting a correct reading at your guage. Maybe something got in the water line from your motor to your gauge. This line needs to be removed when you do a water pump R&R. Maybe when put back, something got in the line.
    I am getting basically exact reading from old school pressure gauge and smartcraft gauge. I assume smartcraft is from inside the engine somewhere. I will continue the process of elimination. Water pump assy was first..

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    #20

    "Recently changed my jackplate".
    "Same setback".
    "First trip out I was too high".
    "but guarantee my motor is not too high".

    But...……..

    "I’m just refusing to buy into the theory of motor height"







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