Water pressure??

[smokeyjoe 2]

I think I have a problem with the water pump on my Merc 150!! At low rpms a have about 5 psi and it goes up to about 17-18 psi at about 40 to 45 mph or 4000 to 5000 rpms, after that it drops down to around 7 or 8 psi or lower and jumps around a lot!! The tell tale is very warm but not real hot, I mean you can stick you finger in it and not get burnt!!Is this a water pump problem or something else??? Oh yeah , it does take about 5 seconds for it to start peeing out when I crank it up!!

 

[JB]

Re: Water pressure??

Moving to Merc troubles.

 

[Hooty]

Re: Water pressure??

Kinda tie this back to your other post about trimming out. What it sounds like is you're starting to suck air into your water pick-ups. Where is the cav (antiventilation) plate in relation to the bottom of the boat. Sounds like it might be a little high.<br /><br />c/6<br />Hooty

 

[andrewkafp]

Re: Water pressure??

It may be that at the higher revs, knowing how the impeller vanes bend right back reducing the water pressure but increasing the flow (More volume) it may be normal. If you are able to touch the stream without discomfort, I would say it's cooling properly.

 

[KCLOST]

Re: Water pressure??

That sounds a little low, but not much... Mine runs about 10psi at no wake speed (1000-1100 rpms) and up to 20 at higher revs...<br /><br />Check your poppet valve, it could be stuck open a little....<br />It will take about 5 seconds to get pressure up to the guage fitting, by the way...

 

[smokeyjoe 2]

Re: Water pressure??

Poppet valve?? Where's that at and how do I check it???

 

[Hooty]

Re: Water pressure??

The "jumps around a lot" sounds like air.<br /><br />c/6<br />Hooty

 

[KCLOST]

Re: Water pressure??

When you say it jumps around a lot, are you talking about above 4500 rmps?<br /><br />By the way the poppet is on the starboard side of the engine down low, below the switchboxes... There are a few bolts that hold the cover plate to the block....<br /><br />Are you overheating??? If not you may not have a problem...

 

[smokeyjoe 2]

Re: Water pressure??

yeah, above 4500 is about the time it starts jumping up and down!! What do I need to check for on the poppet valve?? I Don't think I'm over heating, yesterday when this happened I stopped and put my finger in the stream coming out of the motor and it was hot but it didn't burn my finger !! I don't think it's over 180 deg. if that much!! Felt kinda like sticking you finger in a hot cup of coffee!!

 

[KCLOST]

Re: Water pressure??

There is no reason NOT to check the poppet... Just take it out and clean/inspect... There is a cover plate, a divider plate, a diaphram, the poppet valve itself with a spring, and a grommet or two... Just inpect and clean...<br /><br />By the way, what happens to the pressure at 5500rpms plus?

 

[m_bickle]

Re: Water pressure??

More info on the motor would help to better diagnois your problem to tell you how best to proceed.

 

[smokeyjoe 2]

Re: Water pressure??

I fellow I know told me to try and plug the top two holes on each side of the water intake and that would fix the problem with it jumping around!! He said they were sucking air!! So I tried it and it worked!! The pressure stayed pretty steady while cruising yesterday , around 13-15 psi at 45-55 mph!!

 

[KCLOST]

Re: Water pressure??

Nope, don't plug any holes.... Make sure your motor height is correct to take care of that possible problem.....<br /><br />By the way, if you're not overheating you don't have a big problem yet... But it's good to check everything you can...<br /><br />Good luck...

 

[Hooty]

Re: Water pressure??

Hummm. So it wuz air. Actually, plugging those top holes is pretty common practice when running a high X dimension. If you're running under 80mph it's a lot more desirable then a low water pickup.<br /><br />c/6<br />Hooty