The water coming out the pump indicator on my Mid to late 80's 200 Merc is very hot!

mercman2 · Sep 16, 2012

I noticed the water coming out of the pump indicator was so hot you can't put your hand under it. Is this normal? I put a new water pump in it to no avail, still steaming hot. After running it for a few minutes I dropped the lower unit again to look for any obvious problems. When the lower unit slid down I grabbed a hold of the drive shaft and it was hot and sooty. Like exhaust was blowing on it and the water tube. So I investigated further. I proceeded to remove the powerhead and exhaust plates. I looked down the exhaust tube and there were 4 half inch holes drilled all the way through the front of the exhaust tube right where the water tube comes up through the mid-section. I thought this must be a bad attempt at a performance upgrade but when I tore my second mid-section down.(one I had laying around) I found the same 4 holes. I guess this typical for a 200 hp Merc exhaust tube? Back to the question why is the water coming out of my pump indicator so hot. The motor runs at about 170 to 180 degrees on the hose. Temp taken with a infrared thermometer. It literally steams in 95 degree weather with 100% humidity. Any help or suggestions would be greatly appreciated.

Scott Danforth · Sep 16, 2012

Re: The water coming out the pump indicator on my Mid to late 80's 200 Merc is very h

start by changing your thermostat. it should be a 120 degree t-stat. then change the impeller while you have the foot off.

mercman2 · Sep 16, 2012

Re: The water coming out the pump indicator on my Mid to late 80's 200 Merc is very h

It has new stats in it. When I got the motor one stat had been tampered with and the other was plugged with hydrilla. I broke one of the stat bolts which led me to remove the head cover to extract the rest of the bolt.The water passages looked fairly clean.

mercman2 · Sep 16, 2012

Re: The water coming out the pump indicator on my Mid to late 80's 200 Merc is very h

It also has a new impeller in it. Did that with the stats. It's actually got hot enough inside the driveshaft area to start melting the top of the guide sleeve for the water tube,on the water pump housing.

aussieflash · Sep 16, 2012

Re: The water coming out the pump indicator on my Mid to late 80's 200 Merc is very h

Your tstats will be 143d and only open at that temp.Thats fairly hot to touch as is mine when on muffs.
Whats your dash temp gauge say,and is it getting hot in river or just on muffs?If your temp alarm sensor is directly below #1 cyl then it will sound at 240d,if its to the side it will sound at 190d.
When you replaced impeller did you re attach divider block and seal with silicone to prevent exhaust entering.
Post a pic of pump area if you can.

Dukedog · Sep 16, 2012

Re: The water coming out the pump indicator on my Mid to late 80's 200 Merc is very h

There are "three" things that need ta be addressed first at tha sign of an overheat on tha V6 Merc. First tha water pump. Replace tha whole thing paying close attention to tha gaskets. Not just tha impeller. Second are tha T-stats. They can be cleaned and checked in a pan and thermometer on tha stove . They will be 143 degree (standard OEM) unless someone has changed 'em. Last is tha poppit. It has to be "CLEAN" and nothing torn or broken. Check fiber and rubber grommet in tha block. Its best to replace it completly since its not a high dollar item. Same with t-stats if there's any doubt. Doing these things usually clears up 90% of overheat problems. If tha problem still appears ya got ta start diggin' a "deeper" that gets a lot more involved..........jmo

Do you have a water pressure guage? Did you see anything out of tha ordinary (like bad gaskets, debis) when you split tha exhaust adapter? Did you pull tha exhaust divider and check?

Oh yeah, those holes are for exhaust relief when tha mid is full of water at idle.........

mercman2 · Sep 16, 2012

Re: The water coming out the pump indicator on my Mid to late 80's 200 Merc is very h

Thanks Dukedog for answering my question about the holes in the exhaust tube. The stats are brand new and the popits are clean. No calcium build up around the grommets causing them to stick. I have a handheld infrared temp gauge with a laser targeting beam. I took the temp readings on the head covers and along side of the heads. Which seemed to get warmer as I went down. 160 to 180 degrees. I'm freaked because the water coming out of the pump indicator is litteraly steaming and it is by no means cold here in FL. I'm already involved lol. I have replaced the silicone on the exhaust divider in the foot. I haven't taken it to the lake yet but I guess that is my next step. I dont get any alarms from running on the hose just never seen one steam from the tell tale like this. I don't have a pressure gauge but the stream is plenty strong.Oh yea and the rest of the water pump is fine.

Dukedog · Sep 16, 2012

Re: The water coming out the pump indicator on my Mid to late 80's 200 Merc is very h

Your sensor is right under number one and reads head (metal) temp. As long as your warning "horn" is good (sensor can be tested like tha t-stats) and NOT going off your good ta go. As far as tha seal between tha "can" and pump area, Its not that critical. I don't run any type of can in my motors and have no problem with exhaust/pump issues. If everything is working right it will not heat tha pump to any extent...I have, on ocassion, melted (just a little disfigured) tha thin guide sleeve when pushing tha lean side on tha motors ("bout 1300+* egt's). But still didn't hurt tha pump.....

You NEED A WATER PRESSURE GUAGE.................Its just as important as YOUR blood pressure!

ChrisBurn · Sep 16, 2012

Re: The water coming out the pump indicator on my Mid to late 80's 200 Merc is very h

I have 89 150 merc, i also noticed the "steam" out of the tell-tale. I do not run tstats. Temp was running 180 + on one side. I flushed head with salt away but still ran hot. I happened to take the hose loose from the tell tell stem that has 3/16 hole. The increased water flow lowered the head temp 20 degress! Dont see any negative effects.

aussieflash · Sep 17, 2012

Re: The water coming out the pump indicator on my Mid to late 80's 200 Merc is very h

ChrisBurn said:
I have 89 150 merc, i also noticed the "steam" out of the tell-tale. I do not run tstats. Temp was running 180 + on one side. I flushed head with salt away but still ran hot. I happened to take the hose loose from the tell tell stem that has 3/16 hole. The increased water flow lowered the head temp 20 degress! Dont see any negative effects.

No Tstats = no pressure = running hot at idle.When up on plane she will run cold due to poppet open and nothing holding water in head to warm up,which will create other issues.Put in a pair of new Tstats and see the difference at idle.
You may have other issues like blockage etc,but no tstats is not the answer.

mercman2 · Sep 17, 2012

Re: The water coming out the pump indicator on my Mid to late 80's 200 Merc is very h

Thanks again Dukedog thats exactly what I am seeing on the guide sleeve. Sounds typical for this year Merc V6. Alright I'm gonna put it back together and go trim it out.Thanks for everyones input, greatly appreciated.I will keep ya'll posted.And I agree aussie if it came with stats you should run stats.Those engineers at merc have forgotten more than I will ever know.Oh and Dukedog this is a customers boat I am working on selling him one.I have a water pressure gauge lots of hydrilla where I go. It's where the big ones live.

mercman2 · Sep 17, 2012

Re: The water coming out the pump indicator on my Mid to late 80's 200 Merc is very h

One other thing is a carb job is on the way before I go to the lake so hopefully that will cool the high exhaust temp a little.

Maxz695 · Sep 18, 2012

Re: The water coming out the pump indicator on my Mid to late 80's 200 Merc is very h

Wouldn,t hurt to change the exhaust port and baffle gaskets. May be leaking water into the block through the cylinder exhaust port. and presuring hot exhaust gases into the waterpjacket

Faztbullet · Sep 19, 2012

Re: The water coming out the pump indicator on my Mid to late 80's 200 Merc is very h

One other thing is a carb job is on the way before I go to the lake so hopefully that will cool the high exhaust temp a little.

If the exhaust plate water holes are stopped it it will reduce the "water wall" that muffles the exhaust and cools the water pump housing and prop hub.....if the alarm/senders is working and not sounding its ok.

Dukedog · Sep 19, 2012

Re: The water coming out the pump indicator on my Mid to late 80's 200 Merc is very h

mercman2 said:
Thanks again Dukedog thats exactly what I am seeing on the guide sleeve. Sounds typical for this year Merc V6. .

Not typical when everything is right on a production V6. Think ya got something going on with tha exhaust adapter plates. There should be very little exhaust on that side of tha can. (water pump side)...........

emoney · Sep 19, 2012

Re: The water coming out the pump indicator on my Mid to late 80's 200 Merc is very h

I have a '96 Force 120 and the tell-tale stream is also very hot. At first my reaction was the same as yours, as on my old Evinrude it cooled off quiet a bit. However, when the Tstats open I'm getting temps in the 140 range so I know it's not overheating. Put it in the water with the lid off and take your infrared thermometer with you and shoot temps again after it's up on plane and see what you get. 180 is a little concerning, but 160s should be fine.

ChrisBurn · Oct 9, 2012

Re: The water coming out the pump indicator on my Mid to late 80's 200 Merc is very h

Is this a possible reason that the water cooled voltage reg failed ( started overcharging) on a 3 hour trip? Idle and operation on this motor has always been good. Installed new reg. I seem to drop a cylinder on a long idle and then it picks up on plane after a few minutes. I thought it might be coil pack. Im going to install new pressure gauge just to see where Im at. Where should pressure be at idle?

The water coming out the pump indicator on my Mid to late 80's 200 Merc is very hot!

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