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Author Topic: Temp gauge for 200 Mercury  (Read 3721 times)

May 17, 2007, 11:34:41 PM
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jdupree

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Temp gauge for 200 Mercury
« on: May 17, 2007, 11:34:41 PM »
I have already posted this on TMD with no help and iboats.com with some opinions.  As you know my 200 CCP has a 1992 200 HP Mercury.  Decided to install a visible temperature gauge.  My motor does have the factory built in sending unit on the port side head near the top.  It has a single tan wire coming from it just like the manual says.  I bought a teleflex gauge with the numbers in degrees.  I hooked up the gauge and took her out.  I noticed that the temp started to climb before I went to WOT.  Coming down from WOT the gauge was showing over 200 deg :shock:   I then felt the tell tale and it was just a little hot but I could keep my hand under it.  The port side of the motor has the temp alarm sensor which according to the manual should sound at 190deg.  Did a test on it and it is functional.  The alarm never sounded and the motor runs great and always cranks right up.  I guess the question is, will the teleflex gauge produce a higher reading and is it compatible with the factory Mercury sending unit :?:

I have never owned a Mercury but I understand that the tell tale runs through the t-stats so the discharge should be sort of hot :?:   The tell tale is also not a steady stream but "pulses" out of the hole.  I don't know much about the motor other than it was well maintained and fully checked out before I bought it.  Water pump and impellor were replaced within the last yearI was told.  Should I trust the teleflex gauge or start troubleshooting an overheat problem which I don't think exists :?:
John L. Dupree, III
1999 Aquasport 245 Explorer - 225 Johnson Ocean Pro
AQABLA84E999
Member #257

May 18, 2007, 09:49:57 PM
Reply #1

GoneFission

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« Reply #1 on: May 18, 2007, 09:49:57 PM »
John:  You should have a steady stream out of the telltale at all times.  If you don't, you probably need to replace the water pump impeller.  

The biggest cause of water pump failure and overheating on Mercurys is running them dry.  You can kill an impeller in as little as 30 seconds of dry running on a 135-275 HP Mercury!  Once the impeller is gone, the engine can't cool the way it needs to...  The 135-275 Mercurys use a high-pressure pump setup that works very well, but must ALWAYS be run in water or with a water supply (muffs or whatever) hooked up.  On the V6 Mercurys, dry = dead.   :roll:

It's not a major deal to replace the water pump impeller; I do it every 2 years as a preventive maintenance thing.  You need a couple wrenches to drop the lower unit, and a helper to put it back on.  Be careful with the water tube and the shift connection when reassembling, but it's basically less than 2 hours beginning to end.  This is one job that even a dealer does not gouge you too bad to do!   :oops:

The Teleflex gauge may have a different response curve than the Mercury sender, so your readings may not be accurate.  However, if the water coming out of the telltale is HOT and you are not getting a steady stream, I would strongly recommend either a new water pump kit or a new water pump impeller.  You can test the gauge and sender by removing the sender, dropping it into a bowl with a couple cups of boiling water, and checking reading on the gauge.  I should read near boiling or about 210 degrees if the water is near-boiling.  

If you have not done it already, get yourself a maintenance/repair manual for that motor - it will make life a lot easier for you!  I like the Seloc manuals, but some folks prefer others.  Check eBay for the right year and model:
http://search.ebay.com/search/search.dl ... category0=

BTW - have you fished any at Weldon this year?  I've heard the stripers are running late...  

See ya on the water!
Cap'n John
1980 22-2 CCP
Mercury 200 Optimax 
ASPA0345M80I
"Gone Fission"
ClassicAquasport Member #209


May 18, 2007, 10:55:18 PM
Reply #2

jdupree

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« Reply #2 on: May 18, 2007, 10:55:18 PM »
John,

Thanks for all the advice.  I think the engine might be running a little on the warm side myself, but not enough to damage the motor.  I already have purchased the Seloc manual.  I am thinking impellor and or water pump because the more rpm's that were run the warmer the motor got.  I have never pulled a lower unit before and the manual should help.  I want to replace the pump, impeller and t-stats.  

The main question that I have is what do I need to unhook from the top end of the motor before I drop the lower unit?  Does it need to be in forward, reverse, neutral?  The book doesn't appear to be to specific in that area.  

I am currently down at Hatteras on vacation.  Wind has been 20-25mph all week :shock:   Not much fishing going on here.  When I get back I plan to tackle the water pump.

I think that I will replace the t-stats, water pump and impeller then see what the temp reads.  Thanks :wink:
John L. Dupree, III
1999 Aquasport 245 Explorer - 225 Johnson Ocean Pro
AQABLA84E999
Member #257

May 19, 2007, 05:11:41 PM
Reply #3

GoneFission

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« Reply #3 on: May 19, 2007, 05:11:41 PM »
I'm not sure what you mean by "unhook from the top end of the motor before I drop the lower unit" - but to remove the lower unit, you remove the nuts that stick up around the top of the cavitation plate.  There are two on each side and one at the front.  The lower unit will then slide off - note that the driveshaft sticks up into the bottom of the engine crankshaft, so it is a good bit longer - this requires the motor to be tilted up to get the lower unit off, and it ain't no lightweight, so it might be a good idea to have some help.  

You need a helper to put it back on, cuz one person needs to align the gearshift connection and water tube while the other is pushing the lower unit in place.  Some folks say remove it in forward, some say remove it in neutral, some don't say.  Just don't move the throttle or turn the shifter while it's off and you should be OK.  Mercury shift linkages are different from OMCs - there isn't any measuring needed, just align and you should be good to go.   :D

Don't forget to put some marine grease on the driveshaft splines when you put it back together, and be a little careful sliding the pump body over the driveshaft so you don't damage the seals.  After you've done this a time or two, you will be an expert!   :wink:

See ya on the water!
Cap'n John
1980 22-2 CCP
Mercury 200 Optimax 
ASPA0345M80I
"Gone Fission"
ClassicAquasport Member #209


May 19, 2007, 06:28:50 PM
Reply #4

RickK

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« Reply #4 on: May 19, 2007, 06:28:50 PM »
Quote from: "jdupree"
Wind has been 20-25mph all week :shock:

I have a chance to take off Monday so we decided to go boat camping for the weekend and wouldn't you know it, the winds here are 20-25 too - when my wife heard it would be 5-7ft offshore (even though we'll be inshore), that cancelled the trip.  Too bad. :cry:
Rick
1971 "170" with 115 Johnson (It's usable but not 100% finished)

1992 230 Explorer with 250 Yamaha

May 19, 2007, 09:37:15 PM
Reply #5

JimCt

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« Reply #5 on: May 19, 2007, 09:37:15 PM »
Take the 170 for a romp if you are going solo.
JimCT
------
\'74 22-2 inboard
HIN:ASPL0953M74J
Chrysler 318
------
\'74 Marshall 22

May 21, 2007, 10:30:51 AM
Reply #6

jdupree

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« Reply #6 on: May 21, 2007, 10:30:51 AM »
Thanks GF for the tips.  It looks like the teleflex gauge is close to where it should be.  Took the boat out yesterday and it never registered over 160deg :?   Ran it at WOT for several minutes and coming down from WOT it read about 160 to 170 deg.  I don't know what happened the time it ran hotter than it should unless the t-stats are sticking or I picked up some seaweed.

I don't know much about Mercury's but the tell tale is a decent stream at idle, but as soon as you give her the gas the stream is very strong.  Will the stream be weaker at idle versus when you open her up :?: Running at WOT the temp actually drops which makes sense.  I think that I will replace the t-stats for starters and see what that gives me.  According to the gauge, the motor appears to be running between 140 and 160deg if the gauge is accurate.
John L. Dupree, III
1999 Aquasport 245 Explorer - 225 Johnson Ocean Pro
AQABLA84E999
Member #257

May 21, 2007, 04:06:48 PM
Reply #7

GoneFission

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Temps
« Reply #7 on: May 21, 2007, 04:06:48 PM »
The water pump is usually OK if telltale squirts at idle.  Yes the stream is considerably weaker at idle then at running speends.  160 degrees is OK for operating temp as well.  Sounds like your motor is running as it should.

Actually the cooling system gauge that works well for outboards is a water pressure gauge rather than a temp gauge.  You will see a clog or cooling system problem quicker with a water pressure gauge that with a temp gauge.  Damage is often done by the time the temp gauge goes high.  

http://www.overtons.com/modperl/product ... 239&aID=19

A V-6 Mercury with a good water pump runs about 5 psi at idle.  There is a port on the engine block that allows a hose to be connected to show water jacket pressure - the hose then connects to the pressure gauge.
Cap'n John
1980 22-2 CCP
Mercury 200 Optimax 
ASPA0345M80I
"Gone Fission"
ClassicAquasport Member #209


May 21, 2007, 05:07:46 PM
Reply #8

jdupree

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Re: Temps
« Reply #8 on: May 21, 2007, 05:07:46 PM »
Quote from: "GoneFission"
The water pump is usually OK if telltale squirts at idle.  Yes the stream is considerably weaker at idle then at running speends.  160 degrees is OK for operating temp as well.  Sounds like your motor is running as it should.

Actually the cooling system gauge that works well for outboards is a water pressure gauge rather than a temp gauge.  You will see a clog or cooling system problem quicker with a water pressure gauge that with a temp gauge.  Damage is often done by the time the temp gauge goes high.  

http://www.overtons.com/modperl/product ... 239&aID=19

A V-6 Mercury with a good water pump runs about 5 psi at idle.  There is a port on the engine block that allows a hose to be connected to show water jacket pressure - the hose then connects to the pressure gauge.


John,

It is funny that you said that.  Mine did have a psi gauge on it when I bought it.  I wasn't sure if it worked but I think it did.  The hose can still be hooked up if need be.  The way mine was hooked up is the hose that comes off the t-stats that goes to the actual discharge had a T fitting that allowed the little hose to be hooked in with it.  Is that where it should be hooked up :?:   If that will work I might go ahead and hook it back up.

I am not sure what temp the t-stats will open on that motor?  I thought around 130deg :?:   If that is the case, isn't 160 running a little hot :?:

Thanks.
John L. Dupree, III
1999 Aquasport 245 Explorer - 225 Johnson Ocean Pro
AQABLA84E999
Member #257

May 30, 2007, 10:32:05 AM
Reply #9

rsh19904

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« Reply #9 on: May 30, 2007, 10:32:05 AM »
Hey john,

just to let you know about the t-stats, the mechanic who worked on it last year also did something to the t-stats to make them work better, actually snipped something off to have them open sooner just to make sure it doesn't overheat.   Also, the water pump was installed in August of 06 and since I had it doesn't have any more than 5 hours run time by me, not including our January trip of course :wink:   Anyway, the mechanic who did the work is Bob Sporay (East Coast Marine) and I have his # here if you'd like.  And the shift rod on the lower is the main thing to look out for when reinstalling the lower, everything else does line up on that motor and there's no clip to connect at the tip of the shift rod like on the omc's or measuring(makes it way easier).  Just shoot me an e-mail abotu Bob if you want his #...oh yeah wife and I are looking to move down that way with her job in the next year..any up and coming towns, realtors to contact?  She wants a "grand old house"..of course I think grand old work  :roll: Thanks,

Ryan
Its called fishing not catching for a reason.  Usually operator error

May 30, 2007, 11:39:48 AM
Reply #10

GoneFission

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T-stats
« Reply #10 on: May 30, 2007, 11:39:48 AM »
I hope the mechanic did not cut the thermostat springs!!  :shock:   This is a one of those things that pop up from time to time...   Some folks believe that if you cut the spring a bit, the thermostat will open sooner.  This is not really the case.  

By cutting the spring, you reduce seat pressure a bit, but you also increase the spring tension force a LOT.  You can do the same  thing with your car - cutting coil springs will lower the car, but the ride becomes much more harsh because the spring tension force goes up (in physics, F= -kx where k is the spring constant of the material and x is the displacement from rest).  

Here's why - the spring force is based on the both the flexibility of the material and the length.  A short piece (say 1" long) of steel wire is hard to bend, but make that a foot long and it will bend pretty easily.  A coil spring is just a piece of wire wound into a coil.  The shorter the length of coil on a spring, the higher the spring rate!  Cutting a spring decreases the uncompressed length of a spring, but increases the force it takes to compress the spring.  A thermostat spring is under compression all the time so you could actually increase the effort required for water to flow through by cutting the spring.  It may move off the seat a little easier, but it will take much more pressure as the cut spring is futher compressed.

So cutting the spring on a thermostat is not a good idea!  Depending on how much you cut, you may find you actually hurt cooling at some RPM ranges.  If you want to dramatically improve cooling, take the thermostat element out and run the thermostat body only - you will have a cool/cold running engine for sure... (Some race engines do this - not recommended for normal use).  

So I bet your temperatures will return to normal if you replace the thermostats with normal ones.   :wink:
Cap'n John
1980 22-2 CCP
Mercury 200 Optimax 
ASPA0345M80I
"Gone Fission"
ClassicAquasport Member #209


May 30, 2007, 12:24:45 PM
Reply #11

jdupree

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« Reply #11 on: May 30, 2007, 12:24:45 PM »
Ryan & John,

Thanks for all the great info in both posts.  I was debating installing 2 new t-stats anyway but you guys helped me make my mind up.  Will go get 2 today and install.  At $10.00 bucks a piece would be stupid not too.  I plan to leave the water pump alone.  I am pretty sure she is pumping good.  By the way Ryan, motor is running great :)   I just want to make sure she is not running hot :!:   Send me a pm or e-mail and let me know where you might be moving.  Thanks for the tips guys :wink:
John L. Dupree, III
1999 Aquasport 245 Explorer - 225 Johnson Ocean Pro
AQABLA84E999
Member #257

May 30, 2007, 03:57:09 PM
Reply #12

rsh19904

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« Reply #12 on: May 30, 2007, 03:57:09 PM »
He didn't cut the springs but looked like something off the end of the t-stat?  Couldn't really see but saw that they weren't corroded or anything like that but at that price, couldn't hurt anyway.    Glad to hear its running well  :lol:   That was an awesome motor, IMHO  :wink:    I'll PM about the locations.
Its called fishing not catching for a reason.  Usually operator error

May 31, 2007, 10:19:50 AM
Reply #13

jdupree

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« Reply #13 on: May 31, 2007, 10:19:50 AM »
Well, pulled the t-stats last night :shock:  :shock:  :shock:  :shock:  :shock:  :shock: One was bent at a 45deg angle and broke at the top, and the band on the front of the t-stats had been removed.  Do you think that might cause a little running hot :roll:
John L. Dupree, III
1999 Aquasport 245 Explorer - 225 Johnson Ocean Pro
AQABLA84E999
Member #257

May 31, 2007, 10:51:09 AM
Reply #14

GoneFission

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« Reply #14 on: May 31, 2007, 10:51:09 AM »
I think you may have found your problem!   :wink:

Now let's load the boat up and go fishin'!   :lol:
Cap'n John
1980 22-2 CCP
Mercury 200 Optimax 
ASPA0345M80I
"Gone Fission"
ClassicAquasport Member #209


 


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