V6 200 Weak Tell Tale output

[Daz]

Hi

First of all hello and may I say this is a most excellent forum

I have been reading through a number of posts along the same subject and I am not entierly sure if I have a problem or not. I have read Capt. Crunch's post and Fishingdan's posts as they experienced similar things to me.

My understanding after reading posts and the Mariner workshop manual is that t'stats hold the water back in the powerhead until the temperature opens them up and water flows out of the tell tale. The relief value or poppet only comes into play once the water pressure pushes it open.

First question - upon opening the poppet does the water come out of the 2 ports on the rear of the leg (yellow arrow)?

Second question - Once the poppet opens is this the source for the water that comes from the side of the block (red arrow) Is this the exhaust manifold or something?

I have a Mariner 1986 (according to the serial number but has been rebuilt) and had the powerhead maintained by a few different poeple for the 3 years I have had it. I now am wanting to take more of a hands on role with it. I have changed the plugs and gear oil over the years but now I want to get more involved.

The poppet valve started to pee water from the small hole on the cover. It turned out that the diaphram had split. I replaced the diaphram and the gaskets but kept the original plastic parts and spring. On further exploration I found that some muppet that rebuilt the engine had not replaced the t'stats. So ordered a pair and some new rubber gaskets. At the same time I had a guy change the impeller. I got a full kit. He fitted it as I did not have the time to fit it. I have the small type of poppet and no feed from the top of the powerhead.

Originally with no t'stats the tell tale was strong and warm. Obviously as the water pump was pumping the water striaght out of the powerhead with no restrictions. With the t'stat fitted the tell tale is weak and dribbly stopping when idling at under 1000rpm. I have checked the t'stats and the do open in hot water. I have not got a thermometer so cannot get an accurate temp at which they open. When the rpm's are increased to between 1500 and 2000 more water comes out. If my thinking is correct and the exit from the bottom of the powerhead that goes into the tell tale feed is from the poppet then this increase is due to the increase in pressure. Untill the thermostats open as the water warms the tell tale in my thinking would be weak.

Due to the temperature of the North Sea off the UK being particularly cold could it be that the t'stats are not opening much? Even when I run the engine out of the water using a hose and the muffs it can idle for 15mins without the tell tale increasing after the t'stats open.

There is water coming from the exhaust which is about the same amount as before. When following the boat wakeboarding I can just about make out ( I wear glasses) that the tell tale is strong and that water is coming from the starboard outlet (yellow arrow above). Now with the old poppet valve I am sure that water came from both of these. Though just thinking about it I cannot remember whether this was on wakeboard (25Mph) or on mono ski (35Mph).

Do you think it could be that the water feeding the engine is cold enough to keep the head temp down so the t'stat do not let much water through? Is this possible?

Any comments would be greatly appreciated.

Thanks

Daz

 

[Texasmark]

Re: V6 200 Weak Tell Tale output

In your first picture, at the top of both heads are rt angle fittings connected to a 3/8" hose in series that goes down to dump below the powerhead into the exhaust housing. This is the normal tstat output and as you said, water will be there only when the stat opens. Stats usually open and close repeatedly when operating at slower speeds in cold water.

Follow that vertical hose (mentioned above) all the way down to where it attaches to another fitting under the powerhead (so the water will go back into the mid-section of the engine. Did you come across a tee that takes a hose off to the starboard side of the engine and is visible from outside with the cowl on? If so this is your pee outlet and it will only pee when the stat lets it................poor design. Very intermittent visual indicator and essentially useless. Don't know why Merc had such a thing.

Son has a 150 Merc which was plumbed as I mentioned (the way yours seems to be) and we moved the pee tube to the exhaust manifold exit tube.

This tube is a rt angle fitting at the top of the engine block directly behind the flywheel (aft) between the cylinders. It too has a 3/8" hose attached to it which goes below the powerhead and dumps into the midsection.

Moving the tee (and replacing it with a straight plastic adapter in it's current position) and placing in the other tube at any convenient spot, will allow the pee to be visable as soon as the powerhead fills with water which is less than 30 seconds from the time you crank the engine. That water stream stays constant and increases in pressure as the rpm's increase. It is not in the stat loop and will not Necessarily get very hot.

The rectangular port you are referring to (with the yellow arrow) is the exhaust relief port which is provided to allow the engine to operate more efficiently (better) at low rpm's where there would be back pressure if the exhaust had to exit the prop and make it's way to the surface.

Since it's exhaust there will/could be some water associated with the exhaust. Don't use this for any malfunction determination. Sometimes you get water there sometimes you don't and different engines have more or less depending upon how the mid section is plumbed.

HTH

Mark
You certainly don't want to run without stats and since you are in cold water I won't explain why cause you said you put them back in.

 

[j_martin]

Re: V6 200 Weak Tell Tale output

In very cold water, it is normal for the pee stream to be real weak at idle.

There just isn't enough engine heat to open the t-stats. Other always open circuits take the warm water away.

 

[Daz]

Re: V6 200 Weak Tell Tale output

Hi Thanks for taking the time to respond. I need to go through what you have said in detail and then respond. I will get back asap

Cheers

Daz

 

[andy6374]

Re: V6 200 Weak Tell Tale output

The yellow arrow points to the relief exhaust ports. At idle there isn't enough pressure to exhaust all the water thru the prop, so at idle speeds it comes out those ports.

 

[fishingdan]

Re: V6 200 Weak Tell Tale output

After beating my head against my engine for a weak tell-tale stream last summer, I have concluded that this era merc v6 engines just have a poor design relative to feeding water to the tell-tale. In cooler waters, these engines just don't seem to put out enough heat at idle to see much of anything coming out of the tell-tale.

It sounds like you repaired the poppet valve diaghram. That is good.

It sounds like your t-stats are operating normally and they are installed. That is good.

Testing without t-stats showed that the hoses from the t-stats are not blocked. That is good.

Seeing the tell-tale get stronger after running on the muffs for 15 minutes also sounds right.

Do you have a temperature gauge? If not get one. A water pressure gauge would also be handy. I don't have one yet.

Unless your experiencing some overheating, it sounds like your engine is operating normally. The waters I boat in are on the cool side as well and I only see an intermittent strong tell-tale stream after running hard in some warmer water.

The hardest part of these cooling systems is undoing all of the work of previous "mechanics". Many just don't understand what the "normal" state looks like on these engines and they starting running the water lines all over the place just to get a stronger tell-tale.

Good luck.

 

[Texasmark]

Re: V6 200 Weak Tell Tale output

Go back and replumb it like I said and all this "stuff" will disappear.

Mark

 

[mikebatt]

Re: V6 200 Weak Tell Tale output

Thanks for all the info on this thread, very informative. Someone above said this is a design issue for older Merc's. I have a 1999 150 EFI that's plumbed just like this, and I have the exact same issues (no telltale until tstats open, then a weak stream but constant after that). Running with tstats removed yields much higher pressure. So should I just stop worrying about this as it's normal?

I called a Merc dealer who said it was "very not normal", but I think he was just looking for a diagnostic fee.

Any help is appreciated.

Mike

 

[Texasmark]

Re: V6 200 Weak Tell Tale output

Don't want to run that Merc V engine without stats. Right bank top cylinder could overheat due to lack of water. Don't believe me, put it on muffs with the engine idling, stats out and look at the stat holes on both banks. Water will be coming out the port side and nothing out the starboard, hence the top starboard cylinder is not completely surrounded with cooling water.

If you get the pee stream connected as I said, you will have pee as long as the powerhead is full of water, which is what you want, as I said.

If your engine overheats you have an overtemp switch that will tell you so. I too think that the way Merc plumbed this type of engine just plain flat sucks!

Mark

 

[jdupree]

Re: V6 200 Weak Tell Tale output

Mark,

I was just reading this thread about the yellow arrow which is the exaust relief port? My 200 Merc is a 1992 model and those ports on mine are not open. You can see the outline of the ports but they are closed up. Are they supposed to be open?

 

[mikebatt]

Re: V6 200 Weak Tell Tale output

Yeah, I just ran it for a minute without the tstats to see if there was a difference. I also did a stat test and they do open around 140-150 F (they are the 143's), so they should be good. I also tested the temp of the pee water, and it was 120F at idle after about 10 minutes running on the muffs.

I was just looking for validation that nothing was wrong, and I think you are confirming that, so thanks!

 

[CharlieB]

Re: V6 200 Weak Tell Tale output

NO stream is inherent in the factory design, it sucks, but functions.

Personnally, I drill a 1/8 hole in the flat of the flange on the stats next to the 'wall', index this hole strait up on installation and also index the spring so as the gap between the very end of the spring and the 'step' of the first wrap/coil is directly over the drilled hole soas not to obstruct this 'bleed' hole.

Now the engine as a very small stream at idle. I KNOW it has water.

 

[j_martin]

Re: V6 200 Weak Tell Tale output

Merc Design. It will warm up in a minute or 2, even in cold water. If it pees, even like a 1 year old potty training before the alarm goes off, yer good to go.

There are several water paths, and the poppet valve opening covers most of the range of normal cooling. If it gets a little hotter, the t-stats open and let a little more water through. The tell-tale is on the t-stats, so especially in cold water, it would be expected to be intermittent.

With a pressure gauge you get used to seeing it at particular places under different conditions. If you pay a little attention, you'll notice if it ain't quite right long before you lose enough flow to hurt anything. If you start to get too low or too high a pressure, you start looking for the trouble.

A temp gauge would help, though it is often not installed.

Run it bone stock. If you mess around with things like omitting the thermostats, the law of unseen consequences will get you for sure, like cold seizing a piston, or frying #1 at idle.

hope it helps
John

 

[hkeiner]

Re: V6 200 Weak Tell Tale output

I used to watch the pee stream on my motor constantly to monitor/judge whether the cooling system was working OK. I was often uneasy watching the pee stream, as it would take a while to appear after starting the motor, it would change in intensity during idle, and it would also stop at irregular times during idle. I was always worried about overheating. I recently installed a temp gauge and a pressure gauge on my motor. Now I can observe the temp and pressure status from the driver's seat and I can easily see that temp and pressure are OK. I no longer constantly worry about what the pee is doing. These two gauges gave me a lot of peace of mind and I think they were worth the cost and effort to install many times over. Just my experience and opinion.

 

[muleskinner]

Re: V6 200 Weak Tell Tale output

I have the same problem with my 150 Hp v-6 Merc. and it is a 2002 that I just bought.
I got worried and installed a new impeller and it runs the same. I guess its the way they are designed? I've triple checked everything and I still have border line tell-tail after it warms up. Is it easy to install a pressure & temp gauge?
hkeiner, What is your top speed @WOT? Thanks,Jay

 

[hkeiner]

Re: V6 200 Weak Tell Tale output

Is it easy to install a pressure & temp gauge?

It is easy to install these gauges. I installed both in an afternoon.

You can buy a water pressure kit on-line here at iboats. The kit will include the gauge, hose, fittings, and installation instructions. Following is a link to some on-line instructions that may be educational.

http://www.diy-boat.com/index.php?option=com_content&task=view&id=151&Itemid=49


Regarding the temp guage, my boat already had the temp sender installed on the port side cylinder head of the motor and a send wire was already in the wiring harness going to the dash area. All I needed to do was to install the temp gauge in an available gauge hole in the dash and connect the wires. If your motor does not already have the temp sender installed, you can install one yourself on the motor. The method of running a send wire to the dash is dependent on whether you already have an available unused wire in the existing wiring harness.

What is your top speed @WOT?

I am not too sure as I have an air pressure type speedometer, which may not be very accurate. The speedometer reads around 50mph at WOT but actual speed may be less than that. I can say that it goes pretty darn fast for me.

 

[Texasmark]

Re: V6 200 Weak Tell Tale output

Mr Dupree,

Off the cuff I'd say yes they need to be open. But not seeing your engine I can't say for sure.

The purpose of these ports is to allow the engine exhaust breathing room when the boat is not moving. Hard to start and run an engine with the exhaust ports closed and with the boat at rest, without relief ports of some kind, you are doing just that. The exhaust, exiting the prop shaft area would have to overcome the resistance of the water to make it up to the surface and that doesn't work.

Before you get the Dremel tool out, I'd launch the boat, crank the engine, and look for exiting exhaust smoke. Must be somewhere cause you apparently have been running this engine. If you see it, you're good to go.

If you don't I'd ask your local dealer about it.

HTH

Mark