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  1. #1
    Member
    Join Date
    May 2021
    Location
    Lake Placid, fl
    Posts
    35

    Praying 1986 mercury 150 black max xr2 ,gauge says running hot

    I have a 1986 mercury black max xr2 on a 1987 Skeeter spitfire 150 with a 1986 mercury black max xr2 s/n 0b129429. water pressure 10-13 idle 15-20 psi wot 6000 rpm. Running over 4000 rpm temp gauge goes to 240 temp, no alarm though,tested alarm and it works when short ground to wire. Replaced both sending units with oem parts,new water pump,new thermostats,replaced temp gauge. it runs about 160 temp below 3500 rpm in florida with water temp 82 degree lake water temp. Water coming from tale talem ok. Cannot figure out why temp gauge says 240 degree, by the time I slow down get back to shoot it with infrared it has cooled down.
    I have called mercury tech support and they can't seem to give a answer neither. I have tapped a hose from a faucet to the thermostat hoses and flushed engine that way to clean out powerhead for debri if there was any but could not find any. Also replaced water tube bushings up in exhaust plate and a complete new water pump, rebuilt poppet valve also. Hope someone can help me out.
    Just bought the boat and motor and cannot figure it out. When you place your hand on the head it does not seem to be hot, After running wot and it gets 240 degrees on gauge after you shut shut down in lake to idle it cools down fast on gauge back to 160 temp. Hope someone can help me out, its driving me crazier. Don't want to use it till I know its right. Help would be appreciated

  2. Member
    Join Date
    Aug 2018
    Location
    1000 Islands, Ontario
    Posts
    959
    #2
    I think on your motor you have 2 temp sensors for the overheat warning signal. However, there should be another sensor for the signal to gauge that is likely messing up?
    Check out this video.
    2002 Skeeter ZX200
    2018 200SHO

  3. Member lpugh's Avatar
    Join Date
    May 2009
    Location
    Sacramento Ca
    Posts
    5,165
    #3
    Better check for a blown head gasket, hot combustion gasses introduced into the cooling system act this way, Do not continue to run it. A cylinder leak down test will find which cylinder though the heads are very easy pull for inspection
    Thank You Leon Pugh