Water pressure question
 

I have Imco Shorties on a 35' fountain. After the 1st run I had 60 psi of water pressure at wot. I bought the Merc bypass valves and am now running 30psi at wot. As I come in and out of the water it spikes up to 35 psi.

I was told to run around 20 psi at wot. What are you guys running for water pressure at wot? Is 35 psi to much? I don't want to start lifting head gaskets.

Thanks in advance
T.J.

Re: Water pressure question
 

Try a Globe Blue Impeller from www.Boatfix.com
It is of a softer more plyable material than stock. I ran one and never exceeded 25 psig at WOT. 7-8 psig at idle. This was on a Supercharged motor with crossover that has bypass. Before the Globe Blue, I had water pressure issues.
I am going to run the same setup on my new N/A 540. It is a good starting point. I will post results.

Re: Water pressure question
 

RLW,
Do you find that the blue impellers last longer than the black rubber ones? I would like to put these in the SeaRay and want something that will last. Thanks for posting the website for them.
Robert

Re: Water pressure question
 

Thanks for the input.

Re: Water pressure question
 

Stock 502 Mag MPI. 15-20 PSI WOT. 7-8 PSI Idle. Your pressure seems awful high! :eek:

Re: Water pressure question
 

Do you have a p/n for that impeller? I can't find it on the web site.

Re: Water pressure question
 

For the Globe Blue GRW2000 impeller, call Les Hall at BoatFix at
561-848-0193.
He could steer you in the right direction.
Good Luck!
Russ

Re: Water pressure question
 

I used a -10 pop off valve to keep the pressure at 18 at WOT. You can plumb it into the main water supply between the the oil cooler and the cross over. I never had any problems with temperature or head gaskets.

Re: Water pressure question
 

I am running a pair of HP500's with Bravo I's at idle I have 1 to 2 psi and at WOT I am in the 15psi range. Am I out of spec? I never have heating problems. Extended idle it is in the 150 range, and at WOT maybe in the 165 range.

Re: Water pressure question
 

Go Big,
When was the last time you looked at your impellers?
Those numbers seem low to me.
Russ

Re: Water pressure question
 

They were rebuilt at the begining of the season.

Re: Water pressure question
 

toolbox:

What is your speed at WOT to produce 60 psi of water pressure? Where did you install the bypass? In the Merc info we have it says over 30 psi is too much and under 20 psi isn't enough.

Re: Water pressure question
 

I do not know the correct water pressure, but I run about 15 lbs and have never had a problem.
As for the blue impeller, you can run it dry for a minute or 2 without destroying it. You can not do this with the black one.

Re: Water pressure question
 

Water pressure isn't all about the pump speed or the impeller... how much does your pick-up hang down into the water?... If your pick-up is big and hangs low... you are going to get water pressure even if you don't have an impeller.

Re: Water pressure question
 

The bypass is installed per the merc directions. I am running 88. Last year everything was fine then I put on the new lower units and it shot way up there. They have a huge opening on the front of the nose cone. That is where all of the pressure is coming from.

Re: Water pressure question
 

Does it have the pickups on the side also ? I have heard of people pluging the ones in front ....

Re: Water pressure question
 

Big .. you running Circulators ?

Re: Water pressure question
 

I would think that 15 psi is adequate depending upon flow. Low flow would increase pressure and higher pressure may aid the flow if the exhaust is restricted. I don't think proper cooling is dependent solely on pressure.

Re: Water pressure question
 

No, it seems that is low, but I have never had a heating problem. That is why I have never worried about it. I like the idea of the blue impellers living out of water for a few seconds.