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I ran the boat today for about 4 hours and it ran like clockwork (as always). The water pressure gauge is still acting up, or maybe its acting the way it should. At idle it runs about 4 psi. At WOT, its running about 16-18 psi. But then after running WOT for about 10 mins, the pressure starts dropping. It finally levels off about 4 psi. Is this normal. The motor does not overheat or anything. Should this concern me.
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maybe less pressure after prv or thermostats open... -
jukes,
I would suspect the water pressure gauge. 4 psi at idle sounds about right, as does 18 at WOT.
If your pressure was indeed dropping down to 4 psi at WOT, after a few minutes I would expect an overheat condition to occur - the alarm would sound and the motor would go into rpm reduction mode.
I would try to test the gauge by removing the tubing at the sender and then using some kind of an air pump to pressurize the gauge to read 18 psi, and then see if it will hold that reading.
If the gauge passes the pressure test, then start looking at things like water pump (if it has been at least three years, then it's about time for a repair kit), PRV valve - it is designed to open at approx 20 psi, but can stick partially open and allow cooling water to bypass the water jackets and dump out the relief holes.
Also, the spring of the PRV could be weak or broken, and opening before 20 psi - fairly easy to check.
It would be wise to get yourself a Yamaha shop manual to help you with the above procedures.
Good luck [img]smile.gif[/img] ,
Ken KComment
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