Temp and Water Pressure Gauge

I would like to install a water pressure and temp gauge on my 90 hp 2 stroke Yamaha. I can only find one port to connect to on the block. Is there a way to tap a hole in the thermostat housing for the temp sending unit?<br />Ed

Re: Temp and Water Pressure Gauge

Ed You won't have to drill. I just put one on mine and the kit gives you several ways to attach the sender. I used the (take a headbolt out and put it thru the bracket method and it works great.) You'll see when you get the kit. Good luck. Wad

Re: Temp and Water Pressure Gauge

Wad,Thanks for the reply. I am not sure I understand. But I presently have the temp sender in the standard opening in the block [dont have the instruction sheet]. I purchased a water pressure guage and the kit did not come with instructions. I am told that in the 90hp block there is only one port to hook up to. Are you saying there is more than one way to hook up a water pressure and temp sencer to a single port?<br />Could you E-mail me the instructions that you are refering to? Any help woul be much appreciated.<br />Ed

Re: Temp and Water Pressure Gauge

Your engine has a tell tale line. The water pressure gauge generally T's into that line.

Re: Temp and Water Pressure Gauge

where did you guys get the temp gauges at i am looking for onr for my 2003 yamaha 4 stroke

Re: Temp and Water Pressure Gauge

Upinsmoke, The kit for the water pressure gauge came with a treaded fitting. Can I just T into the tell tale line? Will this be the same pressure as coming off the head?<br />cory, If you go to the Yamaha web site you will find all their gauges for all of their motors. Get the model number and look for the best place to buy; e-bay, iboats, ect.<br />Ed

Re: Temp and Water Pressure Gauge

Pressure in most engines will be the same regardless where you tap into the cooling system. The tell tale is actually a "controlled leak" in the cooling system so pressure will be the same and read the same no matter where you tap in. I have the same situation on my Merc. Temp sensor is in the only other threaded hole. I used a 1/8" NFT brass nipple in the tell tale hole. put a brass T on the nipple and then attached the tell tale and pressure gauge feeds to it. Connections are all metal -- no plastic. You can also use a plastic T as well. It will work.<br />Cory -- you can get water pressure and temp gauges right here on iBoats.

Re: Temp and Water Pressure Gauge

Upinsmoke, thanks for the explantion and the great suggestion. I will be installing a T connection this weekend.<br />Ed

Re: Temp and Water Pressure Gauge

water presure gauge sounds great, but what is it used for, why would you want to monitor the water pressure. thanks

Re: Temp and Water Pressure Gauge

The water pressure gauge will read in psi. It will tell you the realitive health of your water pump. As the pump wears the pressure will decrease.<br />Ed

Re: Temp and Water Pressure Gauge

I doubt very much that you will get a relevant temperature reading or pressure by tapping into the telltale bleed. The indication there is only that the water pump is working. It will not tell you how much pressure is in the water jacket nor what temperature it is. I could be wrong but I think the pressure and temperature after the telltale bleed from the water jacket could be quite different from that in the water jacket.

Re: Temp and Water Pressure Gauge

Adam -- Outboard cooling systems are not closed like a car. Water constantly flows through the system although the thermostat and popit valves control the flow to maintain temperature. As I pointed out, the telltale is a controlled leak in that system and all other water excapes through the exhaust and the relief holes at the back of the engine. There will be little or no difference in pressure regardless where you tap into the system. In fact you will probably get the most stable and meaningful reading at that port whether you T into it or eliminate the tell tale and use that port for pressure readings. The idea here is to install a new water pump, check the pressure and then as the pump ages you can compare the original reading so you can determine when its time to replace the impeller. Teleflex and thousands of boaters can't be wrong.

Re: Temp and Water Pressure Gauge

Hi Upinsmoke. From a pressure point of view equal pressure in the telltale will only be the case if the apperture of the bleed is the same size or smaller than the bleed feeding it. Any larger and pressure will be lost. Still, if it works it works.

Re: Temp and Water Pressure Gauge

Agreed! -- The tell-tale is the smallest escape route in the system so you are measuring the pressure in the system feeding it. Now if the tell-tale were fed directly off the water pump this gauge would serve only one purpose. That being the water pump is working. In this example water might not be getting to the engine. But on the other hand the tell-tale might says it is. Still, the tell-tale merely indicates water flow through the system -- but is it at 5 PSI or 30 PSI). Tapping into the tall-tale provides the best indication since it proves the block water pressure is OK or not ok. While I've not actually tried this, (but I will as soon as the ice leaves our lakes) measure water pressure using a "T" in the tell-tale. That's easy enough as that's how my gauge is plumbed. Then measure pressure with the tell-tale plugged. I doubt you'd see a change in the reading since the other two escape routes are much larger than the tell-tale. Again, the pressure gauge is a tool to indicate "relative" health of the impeller. Regardless where the gauge measurement is made if a new impeller produces a reading of 5, 10, or 50 PSI and two years from now it reads 3, 5, or 25 its an indication that the impeller needs to be replaced. You can pump water through an engine at any pressure and it can still run hot so the gauge is not a total "overheat" preventer. It works best in conjunction with a temperature probe. Just my views and experience on this topic. I'm certainly not an expert in hydraulics.

Re: Temp and Water Pressure Gauge

Upinsmoke, I am enjoying this discussion and value your input. I still see only little value in the pressure gauge as the readings will vary depending on the temp of the water and the opening of the thermostat etc. The operation of the pump can be witnessed by the telltale. If there is water in the system there will be a telltale and replacing the impeller each 2 years is a good preventative. The real useful info that I would be after is the temperature thus a temp gauge.

Re: Temp and Water Pressure Gauge

I have a question, where I live we have alot of silt in the river, we run jet boats. I have a 2003 yamaha outboard jet. sometimes if we are sitting and fishing for a while silt will get in and plug the teltale hole right at the end where it comes out. My question is, if this gets plugged will the pressure on the gauge go way up. If so the gauge would help. I could look at it and know right away that the teltale hole is plugged. sometimes with our tops on its hard to look back at the teltale hole.

Re: Temp and Water Pressure Gauge

Adam1 your last point is well taken. This is why I want a temp and water pressure gauge. Yamaha only made provisions for one or the other. I thought that moving the temp sensor to the thermostat housing would give me a opportunity to use the head opening for the water pressure. But it would be much easier to tap into the tell tail then trying to tap a metric tread into somthing that was not designed to be tapped. Great discussion<br />Ed

Re: Temp and Water Pressure Gauge

You can also have water dribbling out of a garden hose but there is not enough flow to water your flowers. The tell-tale provides an indication of flow -- not pressure. A pressure gauge also eliminates the need to operate the boat looking over the stern when you can concentrate on the forward path. Your gas gauge wiggles, your voltmeter moves and as you say so will the water pressure gauge. So what, its verifying the water pump is producing sufficient pressure. If those readings (like voltage and oil pressure) begin changing from what you obsered as normal thats the indication that something is amiss and it will almost always be the water pump impeller. The tell tale is only capable of telling you SOME water is getting through the engine. Pressure gauges are installed by people that have their engine height set for optimal performance. Get too high you begin to lose water pressure in certain maneuvers. I've also seen many tell-tales plugged by debris and the owners wring their hands wondering if they cooked their engine. Fact is a pressure gauge would tell them they didn't as the clog is generally at the restictor fitting in the engine cowl. The pressure gauge would indicate the sytem has sufficient pressure and you don't even have to slow down. It is still one of the most overlooked gauges and whether you want to believe it or not, is the best indicator of water pump performance and condition. You seem to be convinced this gauge is not a necessity. If that's the case don't install one. Of if you do, install it as you wish. This post is getting long. Read my next one regarding temperature gauges.

Re: Temp and Water Pressure Gauge

Regarding temperature gauges. What type of gauge are you looking at? Cylinder head temperature or water temperature. The senders are not the same. How accurate do you think those gauges are? Do they move depending on operation? You see -- you are on both sides of a discussion. I happen to have a temp gauge that reads "C----H" with hash marks at 1/3, 1/2, and 3/4 scale. Where do you think that gauge should read? If you find a gauge calibrated in degrees what should that range be? Just in case you are interested, before you install that temp gauge I suggest you bench calibrate it as unless you do, you will have no idea what temperature the engine is really running at and the temp horn will tell you the engine just cooked about the time your gauge is mid scale. I've calibrated two temp senders in the last couple of weeks. I've checked them in 5 degree increments using a digital thermometer and a digital ohm meter. At any given temperature these two sensors varied all over the map. 15 ohms can mean a 5 to 10 degree error in temperature and that doesn't include any error in the gauge itself. To the defense of the temp gauge, it too provides a "relative" indication of what's going on with the engine. When things vary from the "norm" take heed as something is up. Temp gauge, the pressure gauge, and the tell tale work in unison to provide the data you need to ensure your engine lives long. Bye! All a new water pump every two years proves is that you have a new water pump. Does it work better, worse, or the same as the old one did, or the one before that, or the original. Without a pressure gauge you have no idea.

Re: Temp and Water Pressure Gauge

It has all been said. Great discussion!