Low Water Pressure (98' Merc 225 Promax)

[topjetsales]

Hello, I just lauched the boat this morning (22' Velocity) and at idling or up to 5 to 10 mph the psi for water pressure is fine and looks to be coming out of engine just fine. Once I plane off though and the rpms go up, the water pressure drops on gauge and the engine still has water coming out but looks to be not enough. Engine alarm goes off. Any ideas??? thank you

[wired247]

Your motor is too high. Your water pump impeller is no good. Any combination of those two things.

[topjetsales]

Thanks for reply...I have not changed to height of motor in 6 years so it can't be that. The local merc marina did the work for me over winter on the water pump. Does that happen from time to time that newly water pumps to just be defective?

[wired247]

They can get installed wrong. Theres a key that goes on the shaft to hold the impeller. If it drops out when the impeller goes on you'd lose pressure. If the seals on either side of the tube drop out or aren't installed right you'll lose pressure. If chunks of the old impeller clog the tube up it could lose flow which would show as low pressure. If the intakes are clogged you'd show low pressure.

[topjetsales]

Thanks...so just to give a little more detail on what happened to maybe narrow it down...when going 5-10 mph, the water pressure is moving just fine on gauge and as i apply more power on and off, the gauge goes up and down from 5 to 10 psi but as soon as i plane off...the needle completely drops to zero or poss 1 or 2 psi. It was very consistent for I tried several times. Thank you again for your time

[wired247]

troubleshooting 101. Look for obstructions in the inlet. If they arent there then drop the lower and see if all the seals and gaskets are where they need to be. What lower do you have?

[topjetsales]

Also, it looks to me that water still comes out of the engine for a time and then seems to drop off

[topjetsales]

Its a Sportster

[wired247]

It sounds like you are sucking air and losing pump prime but you could have obstructions in the inlet. Check the inlet holes and the gaskets.

[rock]

Its a Sportster

That's your problem. A Sportster is a Harley Davidson. A sportmaster however is a fine gear case. I would inspect the transfer passages for a broken o ring. Seems you are losing pressure as the gearcase rises and those transfer passages do come out of the water when on plane. It could also have a blockage as 247 suggested. Good luck.

Rock

[tlwjkw]

Fluctuation is usually a sign of air. Blockage usually a shows up as high and/or fluctuation. First thing I would do is completely replace tha whole pump with an oem. Just an impeller with used gaskets, grommit might not work......go from there.

[topjetsales]

Just was able to get back to computer...I really appreciate your time and advise. I scheduled service for it next week. Have a great week wired

[topjetsales]

Thanks for your reply...I'm having someone look at it next week. Appreciate the help

[topjetsales]

Taking lower unit out and seeing whats going on next week...thank you much!

[H20WKD]

Had a similar problem, I didn't Form-a-Gasket the gaskets to the plates....:confused:http://i60.tinypic.com/2ecncz8.jpghttp://i61.tinypic.com/1zdomms.jpg

http://i60.tinypic.com/rs6d7c.jpg


Bob

[topjetsales]

Taking lower unit out and seeing whats going on next week...thank you much!

Thank you to all that responded and helped...the local mechanic showed me a piece of gasket that was not seated properly in the plastic water tube. Some how it got crushed and plugged it up so engine wasn't getting enough water flow at high rpms. Again thank you all...enjoy the weekend!