cooling questions v-6 merc 150 '84

I decided to change the t-stats and poppet valve as routine maintenance, and I noticed two things. 1) the t-stats had been clipped off leaving just a little ring of metal and 2) the poppet valve diaphragm was torn. Well I've replaced the parts thinking I've really solved some problems, but now I've got hardly no pee stream and it comes out really hot and the cylinder block seems really hot to the touch. The new t-stats said 195 on the package I thought outboards would run cooler than that. Before I changed these parts I could pee 5 foot out and it would drill a hole in the ground it was so forceful. So whats going on? thanks. Oh yeah I checked the new stats in hot water and they opened nicely.

Re: cooling questions v-6 merc 150 '84

sorry thats 143* on the stats. I'm going to measure the pee water temp.

Re: cooling questions v-6 merc 150 '84

right at 140* on the pee water

Re: cooling questions v-6 merc 150 '84

Son has a '95 model. Doubt that much has changed.

143 is the right (opening) temp....stamped on the pellet. 195 is the temp that the overtemp alarm switch is set to and is supposed to close and sound the overtemp solid alarm.

140 on the pee water sounds right if the pee is plumbed off the stat output. Easy to tell. You know where the stats are as you changed them. The cover on the stat has a hose connected to it....on ours, the right hose tees into the left connector (at the stat) and one hose goes down and out into the mid section.

Follow this hose and if the pee tube is teed off it (about half way down) then your pee is 140 because the stat has to open for you to get any......that would be normal operation.

140 is hot. Most domestic hot water heaters, with thermostat set to Normal (center of range) are setup for 140.

If you don't like the arrangement and want pee faster and cooler get in the archives and look up threads I have written about the subject.

Mark

Re: cooling questions v-6 merc 150 '84

TexasMark thanks for the advise I would like to use your arrangement with the exhaust manifold exit tube, but there is a problem. The place were you describe the tube on my motor has a piece of copper tubing coming out of a fitting and it is pinched off and cut. Were would this line normally go and why would it be cut? Thanks for any advise.

Re: cooling questions v-6 merc 150 '84

dadgummit, If your simply trying to increase the telltale flow the proper way to do it is to enlarge the slots in the thermostat, the reason the Mercury Marine put them where they are is in the mid 70s they had a problem with steam domes burning a hole through the top of the cyl block into the top cyl. they then moved all telltale to the top to prevent the steam domes from ruining the blocks

Re: cooling questions v-6 merc 150 '84

Yeah Laddies I might go that route, but the pinched off copper tubing has me worried. Would this normally be plumbed to something?

Re: cooling questions v-6 merc 150 '84

I hope this picture came through. What is this supposed to be plumbed to? Thanks.

Re: cooling questions v-6 merc 150 '84

Without seeing it it's kinda hard to say what it is, there is nomally nothing in the exaust cover ck here http://www.mercruiserparts.com/Show...=110&bdesc=EXHAUST+MANIFOLD+AND+EXHAUST+PLATE
I think someone may have taped the water jacket on the exhaust cover for flushing or god only knows what, goes on with some of this stuff people do on these outboards

Re: cooling questions v-6 merc 150 '84

I just posted a picture the same time you replied. Please look again. Thanks.

Re: cooling questions v-6 merc 150 '84

That is often used to connect a wter pressure guage.

Nothing to worry about.

The modified stats that you removed was someones 'fix' to achieve both a cooler operating temp and a stronger pee stream.

Over cooling an engine can shorten its life, lack of fuel atomizatiion 'washing' the cylinder walls leading to premature wear of the piston, cyl walls, and rings.

You have correctly restored the system to the original design specs. Use the port with the pinched off line and install the water pressure guage, if you know the age of the water pump impeller OK, if not then for good measure replace it, then start paying attention to the the pressure guage and Happy Boating!

Re: cooling questions v-6 merc 150 '84

On the son's '95 V6 150, this port you mentioned is not plugged. Rather there is a rt angle hose barb screwed into it and a hose from it going down the back of the engine and going directly under the powerhead and dumping water into the midsection. The hose is 3/8" dia. We popped the hose and ran the engine and found that this is just a vent for water (water came out of it with the engine running) at the top of the block and as Laddies indicated, makes a nice place to rid yourself of any steam that might have built up.

So, since his engine is later than yours, maybe Merc decided it was a good idea to use this port to allow some flow thru the block regardless of what the heads are doing (stat position).

We didn't like the OEM plumbing on the pee tube as one had to wait for the stats to open to know if you had water or not. So we transferred the tee to the pee hole from the stat output to THIS HOSE.

Now you only have to wait till the block fills with water to get pee. Much better. Only takes about 30 sec to a minute to get water and the pee stream is much more uniform and greater volume.

As far as the stats working or not, they were in series so one could stick and the pee would be no indication of that.

Besides both heads are equipped with thermal sensors and if the water jacket cover gets to 195F the temp alarm goes off. So if you loose a stat you will know it.

Mark

Re: cooling questions v-6 merc 150 '84

Thanks guys I'm going to get a water pressure gage and put it in that spot. Do I need a 0-15 or a 0-30 psi gage? Thanks.

Re: cooling questions v-6 merc 150 '84

Mark, there is only one overheat sender, and it is normally in the starboard head, the one in the port (left) head is for a temp guage, at least on the 88 &89 V-6 models. I don't think that has changed.
On the later engines, the hose coming from the top of the block feeds poppet valve, which dumps water into the exhaust when it open at about 3000 rpm. This is where most people "T" into for a water pressure guage. I don't really know if the older engines had poppets.

Re: cooling questions v-6 merc 150 '84

Yepper it has changed. The port side has a tan/blue wire and the starboard a tan solid. They both go to a terminal post where a single solid tan goes to the warning module to activate the overtemp warning when required.

Much better setup as with only one, on a v engine, if the stat in the opposite bank sticks shut you are dead meat.

Actually the son got a very weak warning light and horn hear awhile back. Tracing out the wiring, the port sender actually develop about a 100 ohm short and required replacing. I was going to dissect it to see how a snap action disc could provide a 100 ohm short but never did.

Mark

Re: cooling questions v-6 merc 150 '84

The disc just goes together forming a circuit like twisting 2 wires together. When it cools down, then opens back up killing the circuit until it heats up again.

Re: cooling questions v-6 merc 150 '84

I worked in an industry where we used them extensively. We called them "Klixons" but that was a registered trademark for a bi-metallic snap action switch.

Was nothing in the can but two terminals, a bimetallic disc, and spring. Heat would cause the bimetallic disc to deform (like the Frog clicker you played with when you were a kid) and short out the terminals.

I guess the spring must have broken and got tangled up between the terminals on the son's.

Dunno.

Mark