Termperature Gauge

P

phishin04

New Member
Mar 20, 2014
10
Canada
Boat Info
2004 Sea Ray 185 Sport
Engines
4.3L Mercruiser
My 2004 Searay Sport 185 has a 4.3L Mercruiser engine. Last year, my temperature would not increase on the gauge. I first tried changing the thermostat which seemed to be the correct fix. I ran it for a few more hours last year before winterizing it. This year, my engine alarm began sounding once I hit 3200rpm. The temperature seemed a little hot (190ish) so I checked the thermostat again. After checking the thermostat in a pot of boiling water, I realized we had the thermostat upside down. Interestingly, the thermostat I replaced last year was also in backwards. Anyways, after correcting the position of the thermostat I found my temperature gauge would not read any temperature. When letting off the throttle, the temp gauge will jump to 175 and then when I accelerate it drops to zero again. This weekend, the gauge would randomly jump to 175/180 and then drop down to zero. The hoses/engine did not feel overly hot. When turning the key off and tapping the gauge, the needle will increase on the gauge to around 130. I also checked the wires of the gauge and although there was no consistency in what I was touching, the gauge would read a temperature randomly. this has led me to believe I may now be dealing with a faulty temp gauge.

any thoughts/suggestions before I order a new gauge? any recommendations on where to order a temp gauge for a 2004 sea ray? I'm in Canada.

Thanks
 
more likely a problem with the temp sending unit than the gauge.....

this test procedure is from the service manual for my engine.....it applies to most all gauges on my boat....it may also apply to yours....if the gauge test good replace the sending unit.....


TESTING
1. Turn ignition switch to OFF.
2. Remove wire from terminal S (SEND).
3. Turn ignition switch to RUN. Indicator needle on gauge should be pegged to the left.
4. Turn ignition switch to OFF.
5. Connect jumper wire from ground terminal to sender terminal.
6. Turn ignition switch to RUN.
7. Indicator needle must be pegged to the right. If not, replace gauge.

cliff
 
Do the steps above and also check to make sure there is no corrosion in the wire harness connector on the engine if the temp pin has some corrosion it will do what is happening to you, when you put the harness back together use some dielectric to seal it, don't get any on the pins it doesn't conduct electricity only seals the connector.
 
I'm still fighting with this temperature gauge issue. I monitored the temperature closely last year while running my boat, as I still have not been able to correct this issue. I've grounded out the sending unit wire and the gauge pins to the right, suggesting that it is unlikely a wiring issue. I also ran another wire from the gauge to the sending unit. The gauge pins to the right when I connect secondary wire from the gauge to the base of the new sending unit I purchased last year. However, the gauge does not move when I touch the wire to the threaded end of the sending unit. Faulty sending unit? I pulled the thermostat out again and tested it - seems to be working properly. any other ideas or suggestions?
 
cannot use teflon tape for installation and highly recommend a 140 T stat
 
Drill a few 1/8 holes in the flange of the t-stat.---------------nevermind the holes...it is a sending unit problem...I should have read closer.
 
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What is the water temp you're boating in? A couple weeks ago I was having a very similar issue with a brand new thermostat so I started watching the gauge closely. I realized what was happening was that as soon as the thermostat began to open the temp would drop off the Guage immediately. After sitting for a while not runnining mine would also come up to temp Thats when I realized what ( I think ) was going on..Ran for an hour and the engine never reached 160 cooling with 5c water. Just a thought.
 
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check for air in seawater entering engine..

you can do this by installing clear hose water inlet.
 
Thanks everyone for the tips. I have only run the boat in fresh water it's been in the same lake for the last 5 seasons - only had an issue the last couple seasons so confident that the lake temp is irrelevant. I have conductivity from the sending unit gauge to wiring at engine block. As noted, I've grounded the sending unit wire to engine block and gauge pins right. I can't, however, seem to get any reading when connecting sending wire to sending unit threads - only when wire touches portion of sending unit that is closest to engine block. Seems that the sending unit will not transfer current from tip where wire attaches to side threaded into engine block. Sending unit part I was sold is a Quicksilver 806490T. Thoughts?
 
Mike Blake said:
Change the sending unit on the engine. cheap enough.
Click to expand...

Do that it's cheap.

How much resistance did you have from the sending unit terminal to engine ground?


The resistance of the sender can be measured to determine the sender's correct operation. Remove wire to gauge. Connect an ohmmeter to terminal of sender and to engine block. Approximate values are: 75 (room temperature) = 600 to 800 ohms; 212 degrees = 55 ohms. (These are single station values- twin station values would be 1/2 these numbers).

If sender is shorted (0 ohms) gauge will read above 240F
If sender has infinite resistance (Open) gauge will read below 120F.

zero ohms shorted out sender.
 
just completed a quick test on both old and new sending units, after removing from engine block. Both sending units measured 700+ ohms at room temp, 250-300 ohms at 83F and 165-175 ohms at 98F. both units appear to be working (at least when not connected to engine block or sending wire).
 
you should post up pics of your t stat housing and how you have the t stat mounted in housing.

is it alpha gen 2 or bravo?

engine ser#

show pic of thermostat sleeve you used and gasket.
 
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Touching the wire to the threads of the sending unit will not read anything on the gauge unless the engine is warm. If you're doing this with a cold engine (wasn't clear from the post) then that part, at least, is normal.

When you replaced the t-stat, did you use a new gasket? Did you use any sealant on the gasket? And, although it was asked above, just to ask again... did you use any sealant on the sender's threads? Using your meter, do you get any readings AT the sender (ground to threads) at various engine temps? Let's try to isolate where the issue is.

Also... just on the off chance that something is amiss... what's the condition of the spring/ball setup? Take them out and look at them - then manually stretch the spring a little bit to make it longer.
 
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i have pics of thermostat in housing, gasket and sleeve but are too large to attach. Open half of thermostat sleeve is facing towards front of engine (4 hose connections). there's 2 gaskets on thermostat - is this normal? I will email pics if you send me email address.

No tape or sealant on sending unit threads or thermostat.
 
What about the gasket for the housing? No sealant?

Should be one gasket on the t-stat, one gasket for the housing. Are you saying you put two gaskets on the t-stat?
 
round cork gasket where t-stat sits. no sealant. other gasket is between housing and engine block - looks like same set up as any mercruiser parts list. I don't actually recall if a sealant was applied to gasket on housing, but it's sealed onto block. it has the 2 metal points on either end of gasket.
 
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