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  1. #1
    Join Date
    Jan 2009

    water pressure guages ..225 Pro XS

    I`ve posted here before about setting up my `94 20' Bullet with the new `09 XS and some of it was about the high water pressure. It was recommended by most to keep raising the engine until 18-20 psi for starters. For reference Paul Nichols recommended for me to start 1 1/2 " below with OTX -4 28. I was getting 28+ psi on wet guage in dash to begin with and raised the engine twice {1/4" Rapid Jack 1 click). So now I`m sitting 1"below and still showing 20-22 + at about 5000Rpm and above.
    I also had the MercMonitor installed with the new engine...feeling kinda stupid now...I never really checked the Monitor water pressure till the last" Click "up on the jack.. It`s kinda hard to see at 70 MPH and and boat is still a bit of a handful. Finally took a look the other day and apparently there is a 4-5 # difference between the wet Guage and the MercMonitor...Monitor is reading 13-15 at 4000and 18-20 at 5000.....while wet guage is about 18 at 4000 and 22+ at 5000 plus.
    I`m just guessing that the wet guage gets it`s reading somewhere between the foot and the main block.....and the Monitor is reading somewhere in the main engine block ...maybe beyond a restriction point such as the thermostats. Would this account for the difference with the Ram effect in the lower unit???? Or should they be reading th same??
    How bout it there Don and the other my thinking all wacky or just my wet guage??

  3. Member
    Join Date
    Jul 2008

    Re: water pressure guages ..225 Pro XS (SNUFFY)

    I have to deal with wet gauges daily, very few of them are correct when new out of the box!!! Have seen some 100# read correct at 100# and some would be correct at 50# on a 100# gauge. We use them up to 5000# and if it is a critical reading we will calibrate it ourself. Which one can you trust i dont know, i do not have any experiance with the merc monitor.. I would get another gauge to keep around to test w/p and see which two reads closest in a pair. This also is true for all the air pressure gauges we rely on for our tires. I bought a fuel regulator 2 years ago because my gauge was 5# off.

  4. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
    Join Date
    Apr 2008
    Greenville, SC (US)

    Re: water pressure guages ..225 Pro XS (SNUFFY)

    I would encourage you to trust the pressure reading from your MercMonitor.

    The water pressure sensor used on your engine is very sensitive, is connected directly to the water jacket of the engine block, and will report ACCURATE water pressure (unlike an analog gauge).

    If you prefer a "needle-type" gauge, consider a System Link (Smartcraft) water pressure gauge (simply connects to the MercMonitor's System Link Harness plug).

    Dual Mercury Master Technician- for Mercury Outboards, Racing & Mercruiser Sterndrives in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 38 years (learn something new every day).
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  5. Member
    Join Date
    Jan 2009

    Re: water pressure guages ..225 Pro XS (EuropeanAM)

    Thanks Don ...I might go the Smart route. I figured the Monitor was more accurate. I`ll watch `em both for a while and see if they are fairly relative thru out the RPM range.

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