temp gage for 99 5.0 barely moves off the peg

99 Stingray

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Joined
Aug 30, 2012
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5
I recently replaced the manifolds/risers, flapper valves, raw water impeller and the 160 degree thermostat. I went to fire it up and started perfectly. I was watching the temp gage barely move. I was still able to place my hands on the risers without getting burned, but did notice some steam (more than I normally see during the warmer air temps. I shut down and checked things out. The left side hoses coming from the thermostat housing were much cooler than the right ones. And the right riser was warmer than the left. Could there be a air pocket causing this? I pulled the thermostat to see if it was installed wrong, but I think the thermostat will only go in one way. The boat always ran at 160 indicated on the gage. any ideas or thoughts would be highly appreciated.
 

Howard Sterndrive

Rear Admiral
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Nov 5, 2008
Messages
4,603
Re: temp gage for 99 5.0 barely moves off the peg

remove the wire from the sender and touch it to ground. If the gauge doesn't pin at max temp with the wire grounded, your problem is in the gauge/wiring. Just touch it once though... violent bouncing of the needle can damage the gauge.

One side is always going to feel hotter - especially on the trailer, because the boat, trailer and driveway aren't perfectly level.

was the garden hose on full to the muffs? no kinks....

since the one cheap muffs episode I had where the adapter piece popped out of the rubber cup (grrr), I now have an adapter I use to connect the hose a bit more positively than muffs, but with muffs, or in the lake, I can also spin the cap off and make sure a healthy amount of water is spraying out
001-4.jpg

the little gardena adapter for my hose stores on my riser there, and if the drive is off, I have an expansion plug that just pops into the gimbal housing water hole.
 

Don S

Honorary Moderator Emeritus
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Aug 31, 2004
Messages
62,321
Re: temp gage for 99 5.0 barely moves off the peg

It's normal for hoses and risers to be warmer on one side than the other. Especially on muffs of at idle.
The first thing you need to do is verify the gauge is correct. Get an IR temp gun and check the engine temp right next to the temp sender on the front of the engine. You may also just need a new thermostat. The old one could be opening early.
 

99 Stingray

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Aug 30, 2012
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Re: temp gage for 99 5.0 barely moves off the peg

Don, thanks for the reply and advice. Ran the engine with the IR gun and monitored the temp. The temp came right up to 160 and held there. I replaced the temp sending unit and will op check first thing tomorrow morning. Thanks again for the help!!
 

99 Stingray

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Aug 30, 2012
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Re: temp gage for 99 5.0 barely moves off the peg

Thanks for the advice. I traced the issue to the temp sending unit. I replaced it and will op check first thing tomorrow morning. Thanks again!!
 

spdracr39

Lieutenant Junior Grade
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Aug 30, 2010
Messages
1,238
Re: temp gage for 99 5.0 barely moves off the peg

Also remember that if your did not use the factory Mercruiser gasket with the brass inserts on the thermostat change the gauge will read low. You have to ground the housing or change the gasket out with the correct type. Mine did the same thing.
 

99 Stingray

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Aug 30, 2012
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Re: temp gage for 99 5.0 barely moves off the peg

Thanks for the reply. Sorry it took so long to say thanks. I overlooked the easiest thing to find! But thanks so much for sending me in the right direction. I changed out the gasket...and boom, 160 on the gage it is!!!!
 
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