Cooling/ Poppet ? 1989 Merc 200 hp carbed

[gss036]

I replaced a lot of the parts during the off season, water pressure guage- temp sender & gauge (complete TelFlex unit, the sender fits differently than Merc, the Merc sender sits in a plastic sleeve where the telflex bolts directly to the head, touching the metal where the Mercury sender does not). Complete poppet assy.
The poppet was the last part, before that I was reading right at the middle (1/2) of the temp gauge, now I am reading between 5/8-3/4. I was out last week and did not like what I was seeing, I came home took the poppet back out and checked it, there is water flowing as the black paint on the new spring was just about all gone and hanging on the spring/carrier. Cleaned it all up and double checked assy, reinstalled it. Ran it for about 2 hours yesterday, temp is still hanging at 5/8, creeping up&down to the 3/4 side of the guage. I am running 10-12 PSI water pressure at 4000-4200, just as the Merc manual says it should be, new water pump less than 20 hrs ago. I wonder if the new poppet spring is a little stronger and not opening as easy? Idleing out of the harbor the temp runs 3/4 on the guage, but yet on hose it will run in the middle or less? I eased it up to 3000rpm once and could see the pressure guage flucuate and temp drop back down very quckly.
Do I have something not working correct or is it the way the temp sended is installed?
Looking for thoughts of where to look?:/

 

[andy6374]

Re: Cooling/ Poppet ? 1989 Merc 200 hp carbed

A couple of comments here:

-If the spring has the correct stiffness you should see a change in the water pressure near 2500-3000 RPMs.

-Are the cylinder heads too hot to touch?

-What's the actual temp of a 3/4 reading on the gauge? The overheat switch is set for 240.

-It seems that these vintage V6 blackmax's (I have an 88' 200, KCLOST has an 87' 175) just run hot. Don't think it is at all uncommon for these thing to run in the 200-220 range, mine does. And many others have reported the same. I think I remember someone here at iboats actually contacted merc and they said this was norma.

 

[gss036]

Re: Cooling/ Poppet ? 1989 Merc 200 hp carbed

The 2500-3000 rpm was where I was seeing the fluciation, I figured that was the poppet opening. I haven't run it with the cowling off, water is a little too choppy, but on the hose I can easily place my hand on the heads and they are not all that hot, maybe 150 degrees, pee stream is a little less. I guess that's why I keep running it. The new guage is broken down into quarters, like a gas gauge, no numbers. I would guess that 3/4 (3/4-full is red lined) is about 180-200 degrees, no temp alarms sounding. I know that works because my wife ran me through a kelp bed a while back and it sounded. If nothing else I may just put the old spring back in a see what happens, it only takes about 1/2 hour to do that.

 

[gss036]

Re: Cooling/ Poppet ? 1989 Merc 200 hp carbed

Still looking for ideas? ^^

 

[Silvertip]

Re: Cooling/ Poppet ? 1989 Merc 200 hp carbed

I'm going to probably start a disagreement but you are comparing temperatures at two different points on the head. The head does not maintain the same temperature across it unless it's run at fairly high throttle for some time and even then it may not equalize. The center of the head will generally be hotter than other areas. Because your are comparing two senders of unknown calibration you may very well notice a difference. Temp gauges, like speedometers are not precise. I've checked many senders and they vary all over the map. An IR gun or temp sticks are required to determine actual temperature.

 

[gss036]

Re: Cooling/ Poppet ? 1989 Merc 200 hp carbed

I agree with you on 2 gauges and 2 different senders, one in each head, that is not the point. I am trying to figure out why changing the poppet increased the temp reading on the same guage. Are the springs giving different load point for release? Just a thought, thanks for your input.

 

[ncfish1]

Re: Cooling/ Poppet ? 1989 Merc 200 hp carbed

Gary;

Food for thought... When you replaced the poppet components, did you compare the spring lenght of the new one versus the old one?
I have purchased poppet components on occasion and found in one instance, the spring longer, causing the poppet vent to dump water. On another one, the spring was a different diameter (no way the poppet could work).
Just a suggestion and I know it's an aggravation to remove the new poppet assy., but you may want to put back the old spring and see what happens. Your primary desire in replacing the poppet is to replace the diaphram and diverter, esp. if operating in saltwater.
A spring is just a spring, but the one that comes with the engine is installed by the factory to operate at certain conditions and tolerences. Springs made from other mfg./etc., may vary.

 

[gss036]

Re: Cooling/ Poppet ? 1989 Merc 200 hp carbed

I may just put the old spring back on. I am going to try and get out again tomorrow if wind permits. I will watch see where the poppet is opening, etc. Thanks for the thoughts.

 

[KCLOST]

Re: Cooling/ Poppet ? 1989 Merc 200 hp carbed

gss,

Your first post on this thread caught my attention.

Your words,,
"I replaced a lot of the parts during the off season, water pressure guage- temp sender & gauge (complete TelFlex unit, the sender fits differently than Merc, the Merc sender sits in a plastic sleeve where the telflex bolts directly to the head, touching the metal where the Mercury sender does not)."

If you are absolutely sure that the old Temperature sender did not touch metal and the new teleflex one now does, that is the reason for your change in readings on the guage.

Note: I have not seen a temp sendor that fits into plastic! However the overheat switch senders do match that discription.

But with that being said, your readings sound normal especially if you are measuring metal temps on the head. Your old sender maybe didn't touch any metal directly, thus you had lower guage readings...

 

[KCLOST]

Re: Cooling/ Poppet ? 1989 Merc 200 hp carbed

I forgot to add that it is better for your engine to run hotter at lower rpms than at WOT... Have you seen any difference at WOT? Let us know....

I would also like to add how simple little things like idling along for a while in very hot air temps or an extra load, or overprop condition can cause this also... I have been running a 25P Lazer 2 on my motor lately. By myself it runs great and readings are around 220F max, mainly at 1100 rpms for a lengthy period of time. But the other day I had a tournament partner in the boat on a hotter than hell, 90% humidity evening and we were cruising out of a nowake zone for a while and I noticed that the engine temp was right at 240F. The weird thing was that the water pressure was right at normal (or close to it) at 10-12 psi. When I tried to get on plane the motor was loading up, but we did git up on plane and it immediately cooled down to around 200-220f... I think I am over propped under the above conditions...

Anyway,
Black max's were designed to run hot at lower rpms to prevent fouling... And they ran just as hot at max....

240+F is the fear factor in either case....

 

[gss036]

Re: Cooling/ Poppet ? 1989 Merc 200 hp carbed

I think before I replaced the poppet assy, I was running at about 1/2 up on the guage, then after the poppet was changed, it went up to the 5/8-3/4 readings. The idle in the no wake zone stayed about the same at the 3/4 mark. I have never had an overheat alarm yet. I wish this new guage read by the numbers but is like a fuel gauge. Other than idleing about 1/4-1/3 mile in the no wake zone all my running is at about 4200 rpm.
I am runnig a 141/2X17 Merc stainless prop, same size as the orginal alum and seems to be the right size.
I will definately watch it tomorrow when I go out.

 

[KCLOST]

Re: Cooling/ Poppet ? 1989 Merc 200 hp carbed

A new spring can easily cause a slight increase in engine temps at rpms levels around 3K. The reason is that if the spring is new and "stronger" than the old, the poppet will be less likely to open compared to before. The stronger the spring the more water pressure force is required to open the poppet.
So it is possible to see the poppet not opening at the same rpm/water pressure levels as it did before with the old/weaker spring. In this case you will see slightly higher temps up to the point that the poppet finally does open. This does not indicate a problem however, actually it is just working as it is suppose to.

 

[ronnieboy]

Re: Cooling/ Poppet ? 1989 Merc 200 hp carbed

my 88 mag2 (xr4) 150 calls for a poppet spring pre-load of 5 to 9 pounds, it changes pressure readings at about 3000, drops from 10 to 7 then climbs to 23 at wot, 5800rpm, trimmed out, temp gauge idles at 140, then drops at wot to 1/4 gauge, i swing a 4blade 21pitch turbo 2+2, runs great. seems like the spring is different like kclost said, he knows his business. good luck ron

 

[gss036]

Re: Cooling/ Poppet ? 1989 Merc 200 hp carbed

I was back out again today and everything is the same. I may try putting the Mercury temp sensor back on to see if it reads different that the TelFlex sensor. Everything else will stay the way it is for now.
I have another small problem to fix. The check valve for the engine oil tank is dripping TCW oil, really makes a mess, so I will order one tomorrow and try to get it changed. I stuck a pencil in it for the time being.