Water pressure gauge on force 120 hp

[Kick]

I plan to install a water pressure gauge on my Force 120 . Can I connect the hose to the top of the engine ? And my pie hole must be closed or can simply be still in use ? Thanks for the comments .

 

[Jiggz]

I have my 125HP configured the same way. Replaced the t-stat housing plug with a 1/8" brass barbed fitting and then ran a 1/8" hose all the way to the dash. I'm using a 0-30 PSI gauge. Usually, at WOT water pressure goes as high as 12~15 PSI.

 

[tommarvin]

Thanks Kick, We Want to add a water pressure gauge on our 1988 Force 125, 1258X4A , Hello Jiggz, the t-stat housing screw there are four, or the very small plug at the very top looking down at the top of the head? part # 19109 Plug, we have a digital temp guage on the way too, can we take out a t-stat housing screw and use hole for a water temp guage, or make a bracket for surface contact to t-stat housing ? thanks for and help.

 

[Frank Acampora]

The slotted stainless plug at the top of the head is threaded 1/8 NPT and is usually where the temp sender OR a pressure fitting is screwed in. This plug is stainless in an aluminum casting and often is very difficult to remove. Plenty of heat and a slotted impact screwdriver helps. Don't heat the head so much that you start to damage the head gasket though.

Just behind the top of the head is a funny shaped cast pad on the block. This pad can be drilled into the water jacket and again, tapped 1/8 NPT for a brass water fitting or a temperature sensor.

I have used surface mount temp. sensors but although they seem to be accurate enough, they are slow to respond so I do not prefer them. You can remove one of the thermostat housing screws BUT there is not enough room to screw in a temperature sensor. Note that the screws are 1/4 X 20 with only 3/8 diameter slotted heads. In fact, you can not use 1/4 X 20 hex head bolts unless they are 3/8 head. The 7/16 heads will not have enough room to get a wrench onto them. I usually replace these screws with either 1/4 X 20 Allen head bolts or OMC stainless bolts with 3/8 heads and built in washers.

 

[Jiggz]

Initially, for me it was a choice between a temp gauge and a pressure gauge. After many researches and some opinions from the forum, I decided with the pressure gauge for the following reasons:
1. A temp gauge by the time you noticed the high temp, it probably had caused damaged to the engine already.
2. A pressure gauge can easily detect a loss of pressure deviation from the norm which could indicate failing on the impeller before it finally and totally fails.
3. A pressure trend readings can create a good reference to determine if impeller or the entire cooling system is losing efficiency or failing.
4. If you are really into technical stuff, you can even place a pressure switch (with a time delay or selector switch) that will auto stop the engine if the water pressure goes down to certain limits.

Since I use mine on saltwater, the biggest problem I encounter is the long sensing hose gets clogged after awhile. hence requires flushing with fresh water after each season. I'm trying to locate a transducer type pressure gage with small enough components to replace the analog one I got. So far, I haven't have any luck. But even then maybe the transducer sensor will also require flushing.

 

[Kick]

Frank, thanks for your answer agian, do you think that try to removing the stainles plug is to high?
do i brake the aluminium case then?

thanks.

 

[Frank Acampora]

No Title

Usually if the plug is stuck tight it will strip before any damage is done to the head. As I said, there is a handy pad on top of the block that you can drill and tap. although it is not very thick you can also drill and tap the thermostat cover right at the back. some have a little round pad there too.

However, try removing the stainless plug first. It may surprise you and come out relatively easily. You said "too high" Did you mean hard as in difficult?

Note that in one photo the pad is actually tapped to 1/2 NPT and a large plug inserted. BTW: NPT is National Pipe Thread. It is still used in the USA but, of course, metric threads would also be good.

 

[Kick]

Hey Frank , I meant if the risk is too high to try to plug the stainles try to unscrew . What could I damage , which may cause major problems. Thanks

 

[Frank Acampora]

Re-reading my answer, I meant that if the plug was too tight to remove, the slot in the plug would strip before you damaged the head. But again, most are so tight that using a regular screwdriver simply will not remove them. This is a case where an impact screwdriver is a great help.

An impact screwdriver is a simple tool, not very expensive, and can be bought at most auto supply stores and Sears. It is hand held and you set the driver in the screw slot and twist. Then you smack the top with a hammer. The combination of shock and twisting forces the driver into the slot and keeps it from slipping while the twisting force is multiplied by an internal helix. It has interchangeable tips and can also be used with sockets.

 

[Kick]

Okay thanks, i do have a impact screwdriver so i try it.
Thank you

 

[Kick]

No Title

Yesterday i did install my water pressure gauge and to lose the plug was no problem. I have now also the option to install a temp gauge.

 

[Jiggz]

Looks good.