Do I want a water pressure gauge or oil temp gauge?

[Renken1600]

Hey guys,

Still learning the ropes on my outboard and boating in general. I have a 89' Mercury 115 4 cylinder 2 stroke... I would like to have a gauge that can either read engine temperature or whatever the boating equivalent is, in making sure I am not overheating.

Am I looking for a water pressure gauge? or an engine temperature gauge?

I have rewired the entire boat and the last wire that is factory, with en eyelet is a tan coloured wire which my manual says is for water pressure sender gauge? Am I correct in that one?

Either way, not sure which one is the best application for me and where 'said gauge' would be plumbed off the engine.


Cheers and thanks in advance!
Parker

 

[racerone]

Water pressure is your best option.----Not sure why you mentioned " oil temperature gauge "

 

[Silvertip]

Tan wire for water PRESSURE doesn't sound right. Water pressure gauges don't use a sender - they have a tube plumbed from the cooling system to a simple pressure gauge. No electrics required except for the internal light. If you really meant water TEMPERATURE gauge, then yes - either a contact type sender (e.g., cylinder head temperature sender) or a sender that screws into the water jacket is needed. Electrics are involved with that gauge (+12V, Sender (S terminal), ground and light (L). Two stroke engines do not have a crankcase and do not create "oil PRESSURE since oil is mixed with the fuel for lubrication. Therefore you can understand our confusion over the OIL TEMPERATURE gauge. Unless you check the gauge frequently, it will not do you any good. The engines alarm system will tell you if overheating or lack of oil from the injection system is a problem. Gauges can help with early diagnosis of a pending problem however. You can add both water TEMPERATURE and water PRESSURE gauges if you wish. Be aware that water pressure gauges have nothing to do with overheating directly. They merely indicate water is not being circulated properly and that overheating MAY result. Water temperature gauges indicate -- well -- water temperature. Overheating is obviously indicated by the gauge.

 

[Renken1600]

Hey guys,

Thanks for the replies. I didn't write oil pressure, but instead engine temperature gauge... either way I was wrong in its application to outboards lol

I think the water pressure gauge is what I am looking for, it sounds like its a simplified way of making sure my impeller is moving water properly.

Is the tube a pitot tube much like a speedometer? I would need to know where to plumb it off of.

I still don't know what this tan wire goes. It was part of the Tachometer harness (purple, tan/blue, brown/white etc). It hung by itself and the rest of the wires were in a rubber socket.

Cheers!

 

[Texasmark]

I just bought a 19 year old boat and have no idea as to when the water pump was serviced. I really don't need to change it for the sake of changing it as others do, annually for some, and that's their preference, fine....their equipment, their money, their labor, their this and their that. I do know the LU was serviced regularly as I changed the oil and it was near perfectly blue-black and no metal shavings. The prop rotates about as smooth as any you ever touched.

I am deaf and with the wind and engine noises I couldn't hear a beeper anyway and can's see an idiot light the size of a pen point on the side of the console, either of which could address an engine problem. My pee comes right off the exhaust manifold and has nothing to do with the combustion chamber cooling, so seeing a stream means nothing.

In thinking it over, I have an instrument panel with 3 mounting holes for instruments: Tach-empty-Speedometer. Perfect place for a temp gauge which I purchased and installed, right smack in front of my nose where I can easily see it and since the stat opens at 143F and the OT alarm kicks in at 195, with a 100 to 250F scale I can see a problem before it becomes a problem.

The sensor is plugged into the cylinder cooling water, adjacent to the top spark plug. Regardless of anything else going on in the engine, I will know the temp of the coolant/block in/of the engine. Everybody has their preference. This is mine and I think it will work best for me to know if and when I have an "occurrence" of a cooling problem. Once I know I have one, then I'll worry about figuring out just what it is.

 

[Renken1600]

*edit* my apologies, I now realize I put oil temp gauge in the title of this post.

Note to self: Have coffee before starting threads.

Sorry guys!

 

[roscoe]

A water pressure gauge kit would include a gauge, 0-15 psi preferred, And a length of tubing.
Tubing is connected to port in block, usually near the thermostat housing.
Tubing is ran along wiring harness to the helm and attached to the gauge.

Should attach at "17" in diagram. You will need to remove the plug in the block, and attach a small
hose barb, then slide the tubing onto the hose barb.

A temp sending unit attaches at "25/26", and connects to a warning buzzer under the dash,
it is usually too quiet to hear when running at speed.

 

[Renken1600]

A water pressure gauge kit would include a gauge, 0-15 psi preferred, And a length of tubing.
Tubing is connected to port in block, usually near the thermostat housing.
Tubing is ran along wiring harness to the helm and attached to the gauge.

Should attach at "17" in diagram. You will need to remove the plug in the block, and attach a small
hose barb, then slide the tubing onto the hose barb.

A temp sending unit attaches at "25/26", and connects to a warning buzzer under the dash,
it is usually too quiet to hear when running at speed.

Thank you Roscoe. I've been using Sierra Amega gauges in the re-fit. They (unfortunately only have a 30PSI) ... what would I be looking at for correct pressure when installed at idle.

 

[roscoe]

Depending on the condition of your impeller,

5-9 at idle
8-12 at 3/4 throttle and above

 

[jimmbo]

I wish they would sell a Water Pressure Alarm with a Klakzon to announce no/low water pressure