1986 mercury 150 black max xr2 ,gauge says running hot

[jrw33862]

Have a black max mercury 150 xr2 s/n 0b129429 on a 1987 skeeter starfire 150 bass boat. Recently purchased boat and gauge says motor is running hot if you run it above 4500 rpm. Below 3500 rpm motor is at 160 temp, if you go above 4000-5000 rpm gauge quickly climbs to 240 temp, slow motor to idle and drops back to 160 within 2 minutes idling. Have replaced water pump,poppet valve,temp sender and gauge twice, new water tube riser seals,new thermostats,and it still does it, the alarm never goes off and have tested it and it works. It has 10-13 psi water pressure at idle and 15-20 psi wot, descend tale tail water stream.
Have never been out fishing in boat until i can get it fixed, I even replaced head gaskets its a v6. I really could use some advice or help, I even talk to tech support and still nothing. When I bought the boat it did not have thermostats in it.

[JOE54]

aftermarket gage ????? test it with temp gun on thermo covers , please use v6 forum one more down for your mtr

[EuropeanAM]

Also note: Most temp gauges used with these are notoriously inaccurate. Often send you chasing "casper problems" (ghosts).

[jrw33862]

Have a black max mercury 150 xr2 s/n 0b129429 on a 1987 skeeter starfire 150 bass boat. Recently purchased boat and gauge says motor is running hot if you run it above 4500 rpm. Below 3500 rpm motor is at 160 temp, if you go above 4000-5000 rpm gauge quickly climbs to 240 temp, slow motor to idle and drops back to 160 within 2 minutes idling. Have replaced water pump,poppet valve,temp sender and gauge twice, new water tube riser seals,new thermostats,and it still does it, the alarm never goes off and have tested it and it works. It has 10-13 psi water pressure at idle and 15-20 psi wot, descend tale tail water stream.
Have never been out fishing in boat until i can get it fixed, I even replaced head gaskets its a v6. I really could use some advice or help, I even talk to tech support and still nothing. When I bought the boat it did not have thermostats in it.

Fixed it ,Ran a separate wire from sender directly to gauge, at WOT less than 170 degrees. The wire in the harness is messed up some how. Works great now.

[JOE54]

factory mercury 2 wire sender ?????