1999 Force 120HP Water Cooling Options

Onegazza

Seaman
Joined
Feb 5, 2019
Messages
56
Hi All,

Got my boat out the water for a good amount of inter maintenance and upgrades (including doing a full re-wire).

I have a question as to what options I have regarding the cooling system. My engine is one of the last ever made, in the last ever batch of the Force engines.

As part of the re-wire, I've been considering adding a temperature gauge. I've attached photos of the top.of the block by the thermostat. I have read in other posts that the existing temperature signal sender on these blocks just activates the buzzer. It would be good to see the engine is running cool at all times though.

On the top of the engine, by the thermostat housing is a brass plug, which I've read in previous posts is where you would install a temperature sender. From my photos, please can you confirm this is the correct location and thread size? (you can see the thermostat housing, the pipe which goes down to the pee hole and, the brass plug)

So, what are my options?

a) install a temperature sender and run a wire to a gauge on the new dash. Any recommendations on brand of sender?
b) any reason why I couldn't use this hole to install a flush port, to flush the engine when off? The boat is normally in a marina, making flushing with muffs extremely difficult and, engine running in the yard is not permitted.
 

topgun3690

Petty Officer 2nd Class
Joined
May 7, 2019
Messages
164
The factory temp sender is actually a thermoswitch that only activates the warning buzzer, grounds out at around 160 degrees. Recently installed a temp gauge and sender on my Chrysler using Faria Beede products. Used the brass plug hole on top near the thermostat housing. On mine the threads are 1/8 inch NPT, probably the same on yours. Ran a signal wire to the gauge. Pretty simple. As far as using that hole for flushing the motor, not sure you could get enough water through there for a good flush.
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
16,555
The older (pre Mercury) used a 1/8th plug I think the newer is 1/4" plug.
You can get an adaptor to make the sending unit fit.
Not enough water to use for flushing.
The trouble with a gauge on the dash is most people don't monitor the gauge panel while running.
I know if I did?? I'd get seasick:(
I've found a louder buzzer or motorcycle horn works good.
Faria makes a gauge.

They don't have a flush or repair station at your marina???? That sucks.
 

Onegazza

Seaman
Joined
Feb 5, 2019
Messages
56
So, my next question is what is the normal operating water temperature on that engine? The manual gives all the specifications, except operating temperatures.

conscious the buzzer on the block will be hotter than the coolant (water) temperature.
 

Onegazza

Seaman
Joined
Feb 5, 2019
Messages
56
The intention is to have both a gauge on the coolant, as well as the buzzer on the block so, an early warning would be given, before it's running too hot. I presume a typical tempersture for the coolant will be 90-110C.
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
23,929
?????-----I am not sure how you can get the water in a NON PRESSURIZED cooling system to 110C as that is over the boiling point.-------Make no assumptions on how these things work !!
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
16,555
The operating temp: the thermostat is set to open at 130d.
The thermoswitch or sensor's set to about 160d
So 130-160 is the range your looking for.

Boiling point for water is 212d

The thermoswitch is part of the early warning system.
It grounds out and sends a signal to the buzzer.

The switch should be tested as often as you have the cover off for any work.
Takes seconds to ground it and make the buzzer sound off.
You don't even need the motor to be on.
 
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