Water Pressure

[LSU24]

Just curious guys on what kind of water pressure you are running on your outboards. Ran mine (Mariner 2.5 200) Saturday, and at all RPM's it stayed between 8-10 PSI. Never got higher, never got lower (except at idle). Had a strong stream running out at all RPM's also. Water pump was changed out 2 years ago.
I know it is time to do a pump, but finances might hold it up till the summer.

Will water temp have anything to do with it? Water was pretty cold Saturday.

Reason I'm asking is, my Evinrude XP150 put out around 15 PSI WOT, and usually did not get below 10 PSI other times.

[Stroker300x]

a 2.5 has less pressure than your used to as long as you have 10 psi at wot you should be ok
would not hurt to have your water pump changed to make sure it is ok
also your gauge could be alittle off

[spider1]

Now I may be wrong here but I think that the pressure on a 2.5 should not be less then 12 psi and on the 3 liters you can go as low a 10.
8 to 10 seems a bit on the low side!!!

Water temp should not make much difference in pressure.

The pump is really easy to change out and if you do it your self it will cost less the $40 for the parts.

[Strokerdean]

On some of the earlier motors Merc ran hi volume low pressure pumps. I has a 99 225efi that I had put the water pickup ears on the sides of the LU and still only had 10-12 lbs at wot. Stock it had less than 10 with a new pump.
I would ask the question on the Merc board.

[spider1]

Hey Dean your 225efi is a 3 liter right?

[LSU24]

I'll try on the Mercury forum also.

[Stroker300x]

I had a 96 260 that never got over 10 psi and at low speeds would be be low 5 psi I never had it to read any more psi
his motor might be kin to my old one

[Strokerdean]

Spider, the 225 I used to have is a 3 lt motor, in never had high water pressure, before I added the pickup ears it ran very low water pressure, the ears helped but it was still lower than the newer motor.

[spider1]

Dean that is what I was saying. 3 liters are low pressure high volume while the 2.5 are high pressure low volume.

And I don't know what to think about Kurt! He more then likely broke something!

[John Jackson]

2.4 and 2.5 motors (140-200 hp) usually put out 18 to 23 lbs of pressure at WOT, unless you are jacked way up. I would start with changing the water pump.

[LSU24]

Does having the low water p/u have anything to do with it? It is about 1/2 way up on the jack plate. Also it has a Hydrofoil on the motor as well. Thinking real hard of taking it off.

A new water pump is in the near future, and I have not gotten enough seat time to see about WOT, so I just wanted to make sure if I don't run it hard if I'll be ok for now. If I can get it to WOT, the pressure would probably come up a little, I was at 3/4 throttle when It read 10 psi, I thought I put that in the first post.

Is changing the water pump hard to do? I have a pretty good mechanical background, and plenty of tools so I wanted to do it myself. Local dealership said they would do it for 250.00.

Sorry to ask so many questions, but I am real particular about maintenance, especially on this boat. Just trying to keep everything running good so I don't have to get the "LOOK" from the wife if it breaks down. Posted this on the Mercury board, and did not get much response.


Modified by LSU24 at 5:42 AM 2/5/2009


Modified by LSU24 at 5:43 AM 2/5/2009

[Strokerdean]

Spider, yes it was a 3 lt,

LSU, you mentioned your jack plate was about 1/2 way up, how high is the motor prop shaft in relation to the pad on the bottom of the hull? You will loose water pressure it it is to high.

[spider1]

I think that you will be fine if you have 10psi and not at WOT!! and a good pee stream. Go Run it and by the way what about the pic!!!!

[LSU24]

I need to measure my engine height and let ya'll know.

As far as pics, I got some, but is was overcast that day and I want to take some when it's clear outside. And I still got some polishing to do. After seeing all the other boats on here, I don't want to bring the forum down.

BTW, how do you post pics on here anyway. Is it hard to do?

[spider1]

Not hard at all. You just need them hosted by some place like photobucket.
You up load them to there then copy the URL address and paste it in your post.

If you look at the pic I have at the bottom of my post, then right mouse click on it and then click on properties you will see the URL address.

[EuropeanAM]

Some of the earlier 3L's will only hold 10-12 psi water pressure. This is different from the later motors, which need to have 15 psi MINIMUM.

If you have BOTH the low water pickups AND side water intakes (common on newer "standard, torquemaster and fleetmaster" gearcases), it is "factory warranty approved and acceptable" to plug three or four (3 or 4) of the water intakes at the top on each side. Requires stainless steel pipe plugs... not too difficult to do.

If this turns out to be your situation, take a look at the post pinned to the top of the 3L High Performance (Mercury) Board. It has information on drilling/tapping and the plugs.

[LSU24]

Mine is a early 90's 2.5 and have the low water p/u's on the nose cone, and none on the sides. I got it to WOT the other day, and it was between 10-12 PSI and not trimmed out all the way. Still had alot of trim left. I am still going to change the water pump, but think I will be ok till then, I just won't run it hard and I'll keep it under 3/4 throttle.