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Old 15-09-2014, 03:48 PM   #1
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Help/Advice Optimax Low Block Pressure

2000 150 Mercury optimax brings up low block pressure on the smartcraft gauges

Only happens when we back off the accelerator ? This brings up a reduce throttle warning and you have to come back to idle before you can accelerate again

At WOT we are seeing 15psi on the smartcraft and manual psi gauge

We have had new water pump, poppet valve kit, stainless thermostats this year and cleaned the strainer

Any ideas what we can do to resolve this ?
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Old 16-09-2014, 09:13 PM   #2
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low block pressure

First thing to do:
Remove the pressure sensor from the block, your engine is 14years, probably mainly used in salt water, I suspect an obstruction on the '' housing'' where the sensor is fitted or the pipe wich is connected to the sensor.
Check the inside of the sensor for any debris or salt concretion.
Check the inside of the traded hole where the sensor is installed.
gently clean all the parts, then reinstal the sensor, use teflon tape on the thread, or loctite like ''thread sealant''.
If not correct there are another possible possibilities.
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Old 16-09-2014, 09:31 PM   #3
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Thanks french Bruno

Put a new water hose between the block and sensor last weekend , hoping that would make a difference, but it didn't

Psi is 0 on idle, engine runs 550rpm at idle ?

Will have a look at the sensor for obstruction

Jason
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Old 16-09-2014, 09:48 PM   #4
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Here a panel for troubleshootings, it's for a 200opti not a 150opti, but the infos are good to find out the problem.
Did you remove the fitting on the block for inspection when the plastic pipe was replaced?
Are you sure the seals on the water pump are ok?
Does the vertical pipe coming from the powerhead to the Pump is well bolted on the exhaust plate? does it move?
do you have the discharge deal on the pump to the vertical pipe OK?
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Old 16-09-2014, 10:06 PM   #5
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Quote:
Originally Posted by Frenchbruno View Post
Here a panel for troubleshootings, it's for a 200opti not a 150opti, but the infos are good to find out the problem.
Did you remove the fitting on the block for inspection when the plastic pipe was replaced?
Are you sure the seals on the water pump are ok?
Does the vertical pipe coming from the powerhead to the Pump is well bolted on the exhaust plate? does it move?
do you have the discharge deal on the pump to the vertical pipe OK?
Thanks Bruno

Yes Removed the fitting on the block

Will drop the lower unit and have a look at water pump and pipe attachments

Jason
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Old 17-09-2014, 11:28 AM   #6
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Be carefull too, you have a crack on the vertical hose, plus one plastic collar mising on the same hose...
Can you borrow another sensor to be sure yours isn't faulty?
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Old 17-09-2014, 11:41 AM   #7
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Quote:
Originally Posted by Frenchbruno View Post
Be carefull too, you have a crack on the vertical hose, plus one plastic collar mising on the same hose...
Can you borrow another sensor to be sure yours isn't faulty?
Well spotted ! Will fix that

No sensor to borrow, if anybody has one for sale would buy it

Jason
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Old 21-09-2014, 02:41 PM   #8
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Bruno thanks for your help, I cleaned sensor and sprayed with WD40 and we now have 1-3 psi at idle

Jason
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Old 21-09-2014, 03:08 PM   #9
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sorted!
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Old 14-10-2014, 12:44 PM   #10
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Looks like you have sorted it.

I had an optimax that had low water pressure at idle.

It was the main pick up pipe that runs through the mid section from water pump to power head, it was copper, when the new one arrived it was stainless.
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