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I'm wanting to put a water pressure gauge on my 115 4 stroke. Does anyone have the diagram of instructions? Also need part number of everything I need.
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Perhaps think twice
I am somewhat of a information freak when it comes to engine operation data so I installed a Lowrance HDS 7 touch, connected it to my F150 and included a water pressure attachment, which is not a cheap addition. I was less than impressed with the results so I did some research and came upon the following on the Yamaha owner Q&A site:
Q. What is the minimum water pressure required for my Yamaha outboard(s)?
A. All Yamaha outboards have a minimum water pressure of eleven (11) psi at Wide Open Throttle (WOT). There are no announced water pressure specs for low or mid-range operation at this time. This is due to our high volume low pressure cooling system design. In fact, you may see zero pressure at idle, as most water pressure sensors start working at 3-psi.
The water pressure information for these engines is practically useless, reading fractions of PSI at idle and low RPM's and well over 20 in the higher RPM range, yet the minimum at WOT is 11 PSI - better, I believe, would be to monitor the water temperature, which is possible with the Lowrance machine and others that can be connected via a NMEA 2k network.
RayComment
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That explains it
Why my newly installed water pressure gauge (mechanical) is reading a fraction of a PSI at idle.
Thanks for posting this Ray.
Might still be worth having the water pressure while underway at mid range RPM? Although, most likely to pick up kelp at low idle.....
Dave
SeattleComment
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Cooling is the main objective but water pressure, and water flow, is needed to ensure proper cooling.
Monitoring water pressure and water temperature (or engine temperature) is just a means to ensuring satisfactory operation of a motor. Monitoring water pressure can alert an operator to the fact that his impeller may be failing, in which case it might be prudent to change it. Temperatures may continue to be just fine.
People get all too hung up over actual values. Probably explains why lots of vehicles have simple warning lamps/alarms that illuminate or sound when there is a problem. Guys panic sometimes when they see a five degree Fahrenheit increase in water temperature.Comment
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Need to know values
Ya the actual values ranges are not readily available too. I could not find anything official, not in the Yamaha service manual, on the temperature range expected. The only values they show in the service manual are the resistance values from the temp sensor.Comment
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I don't think Yam wants folks to see "expected" temperature ranges. Someone would demand that his motor be fixed if it was one degree over whatever range was published.Comment
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Actually these were in the service manual
But they don't indicate what expected temps should be.
at 20 °C (68 °F) kΩ 2.439
at 60 °C (140 °F) kΩ 0.589
at 100 °C (212 °F) kΩ 0.193Comment
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99.9% of Yam users have or will never see a service manual.
Of the .1% that do, 99.9% of them won't know what a resistance value is.
All that most need to know is to shut the motor down if the alarm sounds. All too many just ignore it and keep chugging along. Then cry that the motor is defective and want a new one.Comment
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and another internet myth that will NEVER go away is born.
your Q ands A is NOT based on ANY data published by Yamaha motors.
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the ONLY two motors specifiacally mentiontioned NOT to use a water pressure guage was the old antique 60 and 70 two strokes.
my cat has big whiskers, I cannot lie.
but over the years , ONLY the old 60/70 two stokes used the low pressure high volume system.
another internet myth debunked.
it was also a test question when I tested out of mod 1 back about 2001.Comment
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its the internet.
Yamaha specifically does NOT recommend the use of a water pressure gauge on the 60/70 US market 2 strokes.
however at WOT the spec for most Yamaha is 11 PSI minimum with no maximum specified.
motors without pressure control valves may be excluded.
Like Boscoe pointed out. there is a reason for NOT publishing a spec for temps,pressures and compression readings.Comment
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