What should the water pressure be for this motor? Have replaced water pump and want to make sure it is right. Pressure is 12-14 psi at full throttle on pad. Just doesn't seem to have much at idle and doesn't pee as much as used to either. Just curious if it is ok.

I have a 99 225 EFI. that's what I get. I was told that these Mercs are low pressure, high volume and that 10 to 14 in the norm. I'd look for a mechanic to come on here and confirm this though, just to be sure.

Thought that was correct but just had engine completely rebuilt and don't want to leave anything to chance. Got too much money in it now.

what did your rebuilder say it should be ?

They should maintain at least 12 but if its at full throttle and anything under 15 I always change the impeller. Depending on what kind of water I run they last from 6 months to a couple years.

The 3 liter motors have the larger impeller and run the high volume. The 2.5, 2.4 and 2.0 liters which are from 135 to 200 hp have a somewhat smaller impeller.

my 200 EFI runs about 12-14 full throttle and around 8-10 at idle....thats with a new impeller. I had it checked out and they said everything was "A" ok

At idle have to throttle it up for it to pick up water but then it will maintain it but hardly shows pressure on the gauge. Thought maybe the gauge was bad. Is there any way to boost the pressure. I replace all the parts (housing,impellar,gaskets and o-rings).

My 225 is doing the same thing.

I am not a mechanice but i was told that this is what it is supposed to run, so i would see no need in trying to boost pressure if you already replaced all those parts and you not having any trouble with it. They are low pressure engines and dont require as much as the others

Everyone has opinions...here's one more.

The 2.5 motor runs more pressure/less volume than a 3.0 motor will, so with that..I really like to see 15 minimum at WFO, 12 is just too close to one big sweeping turn from melted aluminum.

I have replaced everything i know to replace pertaining to water pressure and if i get 15psi at wfo its just barely. it usually runs 12-13.....what else can i do to get the 15psi

Im kinda lost on the last two post but your saying at and idle you have 15 lbs of pressure on your gauge??? At 3 miles per hr my 225 has 1 to 2 lbs.and it gets hot and has an alarm from ideling for along time and killing it.I have a propeller every yr and it makes no difference.Darrell

sounds like the normal range....or that s the range my 200 ran for years before upgrading

Normal idle is low..around 2 or so, WFO I like 15, but...here's the big but...gauges do vary.

Just be mindful on long turns, you'll see the pressure drop, just don't let it fall for a long time.

You can also add scoops that help maintain water flow and pressure. How high is your motor? They aid with high mounts. Mine runs 20+ and in turns 15, tight turns 8-10. It's an '87 Merc 200.