Water Pressure

[betzhunter]

I can't seem to find out what the water pressure should be at 3/4 throttle on my 3gmf yanmar. I would like to put a gauge past the sea water pump to check the pressure. Any help would be great!

Thanks , Bub

 

[kloudie1]

Hey, Bub.. Just a couple of observations .. Water pressure just downstream of the seawater pump is going to be pretty low.. I have never measured it but I guesstimate that it will be in the 5 PSI range ..may be a bit more or less.. The problem is going to be interpreting what ya have.. any blockage in the exchanger or elbow is going to raise the pressure.. Without a good base line reading when things are OK, going to be hard to learn anything from a pressure reading.. A flow reading/indicator is a much better way of reading what is going on with the seawater pump/exchanger/elbow.. Therre has been some discussion on the forum here, but I can't locate it.. something like this is what I think would work fine to let ya know how the system is doing:
http://www.ebay.com/itm/Water-Liqui...244?pt=LH_DefaultDomain_0&hash=item2a401e78bc

 

[Don Lucas]

unless there is a blockage I think the pressure would be pretty low, so low that a gauge would be a waste of time for any useful indication of operation

 

[betzhunter]

Thanks for responding guys, I was thinking something in line like a water pressure gauge that would indicate a problem was happening before it got the point of over heating. Something I could monitor from the cockpit. Anyway it could be just a waste of time.

Bub

 

[Allan12210]

Thanks for responding guys, I was thinking something in line like a water pressure gauge that would indicate a problem was happening before it got the point of over heating. Something I could monitor from the cockpit. Anyway it could be just a waste of time.

Bub

Hi Bub,

Kloudie1 has got it. An open ended flow will yield very low pressure. Being the scavenger that I am, I found a 10 gpm flowmeter at a surplus store for $12.00. Having been a process engineer for a time, I couldn't resist and bought it. As you can see, I relocated my water strainer to the front of the engine compartment and installed the flow meter on the outlet. That in combination with the analog temperature gauge can forewarn me of a problem. For the Yanmar 3GM flow is about 2 gpm at idle and just over 7 gpm at 3000 rpm.

My first indication of a problem is always whether or not water is coming out with the exhaust on start up. If not, the flow meter just confirms there s a problem. If I'm cruising I do find myself looking at the analog temperature gauge periodically that I also have in the cockpit. If the temp looks like it is starting to climb, a check of the flowmeter again confirms there is a problem. Then I have to go find the root cause.

Its still a nice addition that just provides a little extra monitoring I find helpful on occasion.

Allan

 

[ALNims]

Hi Bub,

Kloudie1 has got it. An open ended flow will yield very low pressure. Being the scavenger that I am, I found a 10 gpm flowmeter at a surplus store for $12.00. Having been a process engineer for a time, I couldn't resist and bought it. As you can see, I relocated my water strainer to the front of the engine compartment and installed the flow meter on the outlet. That in combination with the analog temperature gauge can forewarn me of a problem. For the Yanmar 3GM flow is about 2 gpm at idle and just over 7 gpm at 3000 rpm.

My first indication of a problem is always whether or not water is coming out with the exhaust on start up. If not, the flow meter just confirms there s a problem. If I'm cruising I do find myself looking at the analog temperature gauge periodically that I also have in the cockpit. If the temp looks like it is starting to climb, a check of the flowmeter again confirms there is a problem. Then I have to go find the root cause.

Its still a nice addition that just provides a little extra monitoring I find helpful on occasion.

Allan

Nice set up. Very well done too. What type/model/maker of flow meter is this?
Andrew

 

[betzhunter]

Hi Bub,

Kloudie1 has got it. An open ended flow will yield very low pressure. Being the scavenger that I am, I found a 10 gpm flowmeter at a surplus store for $12.00. Having been a process engineer for a time, I couldn't resist and bought it. As you can see, I relocated my water strainer to the front of the engine compartment and installed the flow meter on the outlet. That in combination with the analog temperature gauge can forewarn me of a problem. For the Yanmar 3GM flow is about 2 gpm at idle and just over 7 gpm at 3000 rpm.

My first indication of a problem is always whether or not water is coming out with the exhaust on start up. If not, the flow meter just confirms there s a problem. If I'm cruising I do find myself looking at the analog temperature gauge periodically that I also have in the cockpit. If the temp looks like it is starting to climb, a check of the flowmeter again confirms there is a problem. Then I have to go find the root cause.

Its still a nice addition that just provides a little extra monitoring I find helpful on occasion.

Allan

Thanks Allan, that's what I was looking for and yes Claude nailed it. I was interested in the gpm flow at idle and at 3000 rpm so I could also keep an eye on things. I also have a temp gauge in the cockpit and I keep looking at it and checking to see if any rise is occurring.
Thanks again for your picture and for responding,
Bub

 

[betzhunter]

Hey, Bub.. Just a couple of observations .. Water pressure just downstream of the seawater pump is going to be pretty low.. I have never measured it but I guesstimate that it will be in the 5 PSI range ..may be a bit more or less.. The problem is going to be interpreting what ya have.. any blockage in the exchanger or elbow is going to raise the pressure.. Without a good base line reading when things are OK, going to be hard to learn anything from a pressure reading.. A flow reading/indicator is a much better way of reading what is going on with the seawater pump/exchanger/elbow.. Therre has been some discussion on the forum here, but I can't locate it.. something like this is what I think would work fine to let ya know how the system is doing:
http://www.ebay.com/itm/Water-Liqui...244?pt=LH_DefaultDomain_0&hash=item2a401e78bc

Thanks Claude, just ordered one like it.

 

[kloudie1]

Welcome, Bub.. Hope all is good out your way !

 

[betzhunter]

Very good!

 

[Allan12210]

Nice set up. Very well done too. What type/model/maker of flow meter is this?
Andrew

Andrew,

I can't remember the brand of liquid flow meter 0-10 gal/minute (the boat is 45 miles away). The inlet and outlet thread size is 1/2" NPT. Since mine is plastic, I was very careful about how tight to make the fittings otherwise it will crack.

Here are some leads in addition to the link Claude provided:

http://www.ebay.com/bhp/liquid-flow-meter

You just have to hunt around to find the suitable size in the used market.


Allan

 

[eianm]

wouldn't you be better monitoring the outlet water temp.? I saw an ingenius and VERY simple in an issue of the old Bob *****en magazine (was it lattitudes and Attitudes??) where they used a temp sensor out of an old water heater and simply clamped it to the outlet hose and ran a temp. gauge off it- it was like a $20 solution- if you can remember the name of the mag you may be able to google it - t was in their readers tech tips section.