temp alarm issues

[gschultz05]

ok guys here is my problem i have 1986 175hp merc blackmax and the temp alarm sounds off....the solid beep. have had this problem for awhile now and did research after i had virtually replaced entire cooling system did the water pump, impellar, and thermastats, and just did the poppet valve (relief valve) although after i did the poppet the pee came out better and my pressure at the gauge had returned to where it should be and pretty solid before it would jump all over the place. no the problem is i can run the motor all day long at 4200 rpms but as soon as i go over that within moments the temp alarm goes off then i back off the throttle and bring the boat off a plane and the alarm goes off and i can proceed up to 4200 rpm again and run all day at that. what could it be i am getting frustrated with this my next step is to replace the head gaskets cause i have read somewhere that if the gasket could be leaking and that could cause it. i know the temp sending unit is original so could it have a weak spring and activating earlier than it should??????please help

 

[Dave1027]

Re: temp alarm issues

At what temp does the alarm go off? Are you seeing an increase in temp just before the alarm goes off? If not then I'd suspect an electrical/sensor malfunction where it's not a temp related thing at all but something rpm related like higher voltage maybe?

 

[gschultz05]

Re: temp alarm issues

not sure what the water temp is when it triggers the alarm the boat just has a pressure gauge and no temp guage. i believe the alarm is suppose to be set off when the temp reaches about 193 or so but i could be mistaken i dont have my manual handy to research that till tomorrow. i was also thinking it could be a mixture problem if the motor might be running a little lean. it has been a long time since the timing has been checked and the carbs have been looked at

 

[gschultz05]

Re: temp alarm issues

i wonder if the stater is going out

 

[waterwhiz]

Re: temp alarm issues

What timing this is. I was about to post a similar situation regarding my Force by Mercury 120 Hp 1996. Mine also has a pressure gage but no temperature gage. Also replaced thermostat but went with 1 with all the guts out after originally putting in a brand new 102 degree stat which didn't change anything. Our river temperature here in Fl. right now is 89 and my mechanic says can run a "blank" without any problem. The foot pick up was a little covered over but cleaned it all out but nothing has changed. Throttle running to about 4600 and 40 mph then the buzzer comes on. That leaves me with just the electrical sensor in the block also. Can hold my hand on the power head and also out the "pee hole" and sure dosen't feel anything but warm water to me. Anyone know what temperature sounds normal? My next step is using some kind of thermometer and get an actual reading. Maybe we can compare notes as we continue to work out this problem? Would appreciate any thoughts and ideas and from the forum members.

Jay

 

[waterwhiz]

Re: temp alarm issues

Sorry, should have edited my reply a little better. The stat it called for was 120, not 102.

 

[gschultz05]

Re: temp alarm issues

mine are 143 and the water dont feel to hot out of the pee hole on mine.

 

[gschultz05]

Re: temp alarm issues

ill post more stuff as i research more and try to figure this out. gonna be working on it tomorrow morning when i get off shift

 

[Dave1027]

Re: temp alarm issues

At that rpm the poppet valve bypasses the t-stat so it can't be the t-stat. Maybe a poppet that is closing when it's not supposed to? Only way to know is to hook a temp gauge to it. I don't see why any boat with a mid size or bigger motor does not come with them. I watch mine all the time.

Are you seeing any pressure fluctuations before the alarm goes off?

 

[gschultz05]

Re: temp alarm issues

no not really its pretty consistant for the most part i do get some bouncing of the gauge but i do know that the line to the gauge gets a little air in it at times i have to unhook it and bleed it out periodically i need to change the line and i am in the process of buying new gauges these ones are pretty old.

 

[gschultz05]

Re: temp alarm issues

the poppet, spring, diaphram, grommet and bushing thing along with gaskets are all brand new i just replaced them two weeks ago

 

[waterwhiz]

Re: temp alarm issues

After reading these posts and replies, I am still in a situation with my 1996 120 Force by Mercury that I need some more answers. Sunday I replaced the impeller, running a cut out stat, have a water pressure gage but no temp. Still had the buzzer come on at about 4000 rpms. Had the cowling off, could lay me hand on the head, hold it under the pee hole and the exhaust. Felt like luke warm bath water to me. Am I worrying needlessly? Also, where exactly is this "poppet valve" located? What would an acceptable water temp be after throttling down? My pressure gage in hooked up to a fitting on top of the block above the stat housing. With a stat complete (not hollowed out) I use to carry about 5 or 6 lbs. at idol and 18 to 20 full out. With the hollowed out stat, pressure is now down to 2 lbs. at idol and about 12 AFT. Does this sound about right? Guess I am looking to possibly adding a temp gage without removing the buzzer system for the time being. Best places to hook up and should I use a sensor type or ......?Thanks in advance to any and all answers or suggestions.

J

 

[Dave1027]

Re: temp alarm issues

The motor already has a temp sender that turns on the alarm. Take readings with a ohm meter to ground. Are you seeing a resistance fluctuation as you get past 4k?

BTW, isn't this a Force motor? Looks like you posted in the wrong section. I don't really know Forces.

 

[j_martin]

Re: temp alarm issues

The temp sender on these things is a cheezy klixon snap disk switch. They are known to fail in this way. Also, all it does is ground the alarm circuit. That circuit has to get by one open screw terminal, a cannon connector, a couple of other quick connects, whatever install foolishness is under the dash, and the ship pet rat. Grounded at any point for any reason sounds the alarm.

Shoot the bug out, first trying with the 0hmmeter, then maybe disconnecting the switch and see if the buzzer still sounds. If it doesn't, change the switch.

hope it helps
John

 

[gschultz05]

Re: temp alarm issues

is that for the force or the merc

 

[j_martin]

Re: temp alarm issues

is that for the force or the merc

THIS is the F&^)*&)(*& Mercury forum.