water pump

I was out on the lake fishing today in my 374v Ranger with a 175hp 2.5L XRI and I ran it about 5 minutes at 55-60mph and then slowed down and idled into the cove I was going to fish in. I am always looking back at the motor to make sure its pumping water and after the hard run I looked and it was peeing water just fine. So I idled around and after about 2 minutes I heard some hissing and spitting and I turned around and the motor was just spitting water out like it had air in the lines. It was just like a garden hose does when you turn it on until the air gets out. Motor wasn't hot that I know of because the warning buzzer didn't go off. So I put it in neutral and revved it up to about 2000rpm for about 10 seconds and it cleared up and then did just fine the rest of the day.

What could've caused this to happen? Never seen this before. Is this possibly the water pump getting ready to bite the dust? The person that owned the boat before me changed the pump 2 years ago and the used the boat for a year and then it was parked for a year. This motor also has to run for about a minute before it starts peeing water when you first crank it up after its cooled off. I've been told this is the nature of these motors since the water goes through the motor and thermostats before it ever goes out the pee hole so the thermostats have to open up.

Re: water pump

Impeller replacement should be done every two years. If not just for peice of mind. check the LU oil while your at it. I,m not sure but i think there is a by pass that even if the thermostat doesn,t open or starts to fail water will still go through the engine and tell tale. not much but some. you can remove the T-stat and place in hot water approx 130 150 degrees and see if it is opening then remove it and see if it closes all the way. Hissing sounds like the engine got hot check wire connectios on the engine for corrosion unplug the sensor and alarm switches the re plug them back in. use lubricant on the connectors

Re: water pump

Had the same issue with a 2004 optimax 150. Changed the thermostats and the sending unit and the problem went away. After running that hard it is a good idea to not got straight to idle as it slows the water down moving through the water jackets. I have heard of many people who have had problems with mercs getting hot at idle. Some merc dealers and adding a bypass type deal that will keep water moving and things cool will see if i can did it up. Also I also replace the impeller every year and the whole housing every 3.

Re: water pump

Ok, I changed the impeller and housing. Went to the lake and before I changed the pump I had around 3 psi at idle on my water pressure gauge. Now I have 6 psi at idle. Going down the lake at around 30-40 mph I was getting 10psi and now its 15psi. I put the boat in the water and tied it to the dock and it took about a minute and it started peeing. This is how this motor has always done and I really don't like it. I made a run down the lake at 30mph for about 5 minutes and then I stopped and put it in neutral and let it idle. It read 5 psi and was just spraying water and steam out of the pee hole. After about a minute it had a steady stream. Made another 5 minute run and it did same thing. This time I increased the RPMs in neutral about 500rpm and it peed a steady stream, then I let off and it stayed steady. Water pressure is still higher than it was before the pump change. I then idled around for 15 minutes while my fiance sat in the back trolling for a fish and it peed a steady stream just fine.

I've got two questions.
Is it ok to remove the thermostats completely? A lot of my fishing buddies with black max motors have all removed theirs. I have noticed the way my motor is set up the water goes through the motor then to the heads and once the thermostats open it comes out the heads via a 3/8" hose to a tee. From there a line goes to the pee hole and the other line goes down the mid section. That explains why it takes it a while to pee.
Also, I would like to hook up a water temp gauge. Whats the best way to do this and what gauge should I run? Can I just get an electrical gauge and tie into the wires on the sensors in the heads or do I have to install a sensor somewhere and if so where?

Thanks for everyones help

Re: water pump

If you remove the thermostats you run the risk of creating hot spots in the cooling jacket. Replace yes remove NO. Most of those poppet motors just don't pee normal.

Re: water pump

ALL of the water that comes out of the telltale has to go through the thermostats first. It is normal to take from 10 seconds (warm lake) to never (ice water) at idle. It is, however, a very useful item.

If you apply full throttle before the engine is nominally warmed up, you risk quickly expanding the pistons into a cold sleeve and seizing the engine (cold seize). When you're ready for your first hole shot, turn around and check the tell-tale to see if the engine is warm enough to open the t-stats.

A little steam from the beast after a full power throttle down is nothing to worry about.

One caveat. Pull the plugs and peek in. If you have a squeaky clean piston, you have a head gasket or exhaust chest leak that needs to be repaired.

On the temp gauge. There is a temp gauge sensor already on the engine. The stock mercury gauge, as well as most of the aftermarket gauges will run off that sensor. The wire for it should be in the dashboard harness already. It's tan. the tan/blue stripe wire is the temp switch.

In normal operation the temp will vary quite widely, much different than a car engine. Most of the info presented is useless except for overheat, and the alarm covers that.