Engine temperature reading

[Ernie Bubb]

Having trouble with the temperature reading on my engine. The temperature generally reads around 180 to 185 degrees. When I check engine with IR sensor the true temperature in 150 to 155 degrees. Had the yard technicians look at it. Short story, they thought bad wiring harness, replaced that but didn’t fix problem. So I think that leaves the engine sending unit or the gauge on engine. As engine heats the temperature reading on the gage moves as you would expect - so smooth signals coming from sending unit. Does anyone have insights into this problem? Which device is most likely faulty?

Ernie Bubb
At Ease II
Hull 19
Sent from my iPad

[ken magida]

When Forever Young #46 was new she tended to run close to 180. After the exhaust elbow failed it got a little better. After the second exhaust elbow replacement it runs at 160. Go figure.
In any event good preventive maintenance dictates replacement every five years.
Ken Magida
Sent from my iPad,
An intelligent device which corrects my typing.


> On Jul 21, 2026, at 09:48, Ernie Bubb <erni...@gmail.com> wrote:
> Having trouble with the temperature reading on my engine. The temperature generally reads around 180 to 185 degrees. When I check engine with IR sensor the true temperature in 150 to 155 degrees. Had the yard technicians look at it. Short story, they thought bad wiring harness, replaced that but didn’t fix problem. So I think that leaves the engine sending unit or the gauge on engine. As engine heats the temperature reading on the gage moves as you would expect - so smooth signals coming from sending unit. Does anyone have insights into this problem? Which device is most likely faulty?

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[Claudia Allison]

At 2500rpm we always have 158. When we saw an increase in temperature to 168, slowed down and temperature dropped. After returning to the marina found the impeller had one broken fin and needed to be replaced. Thankfully a simple fix and good to change around every 5 years or before. Why good to watch temperature when running, as enabled quick reaction to the situation.
Claudia
SV Salvation #152




Sent from my iPhone

> On Jul 21, 2026, at 10:11 PM, ken magida <kensa...@outlook.com> wrote:
>
> When Forever Young #46 was new she tended to run close to 180. After the exhaust elbow failed it got a little better. After the second exhaust elbow replacement it runs at 160. Go figure.

> To view this discussion visit https://groups.google.com/d/msgid/catalina355/MW4PR18MB5036A5A6B0852D31086C54E5BBC12%40MW4PR18MB5036.namprd18.prod.outlook.com.

[Charlie Wing]

Hi Claudia,

If you mean the raw water pump impeller I believe this should be changed every year ... to prevent failures like the one you described.

Thanks

Charlie

Wing'n It 

Hull #20

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[hvb...@gmail.com]

I agree! Waiting five years between changes is asking for trouble. Preventative maintenance may seem like it costs a little more, but can save a lot of aggravation down the waterway! 

HVB

Sent from the field. 

On Jul 23, 2026, at 8:30 AM, Charlie Wing <charli...@gmail.com> wrote:



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[catalina]

I'll add that if you find that even with a decent impeller that you aren't seeing strong outflow of cooling water, it's time to replace the pump itself.  The inside of the pump body wears out and doesn't make a tight seal on the sides of the impeller.

We changed the pump a few years ago when we noticed the symptoms.  The water flow was night and day after.  

So if you sail in shallow, silty or sandy water, be aware that these raw water pump bodies can wear out faster in these conditions.  We had similar experience on our C320.  To the point where priming after a filter change became an issue.  Priming should not be the same issue on the 355 since water doesn't drain out of the pump feed line on a raw water filter change here.

Jeff Hare

#17 Solstice

Sent from my Galaxy

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[bill pittore]

I agree. I put a new one in every spring before launch. $35 well spent. 

Bill

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[George Southern]

I learned the hard way that just replacing the impeller isn’t always good enough. I bought #101 when it was seven years old and there was an old raw water pump in the spare parts kit, so I knew the pump had been replaced.  But only two years later, the seals failed on the newer pump covering the engine with salt water.  I was not even aware until sometime after when the engine overheated.  This happened just at dusk and by the time I got towed back to my mooring it was very late.  In hindsight, I should have then sprayed all the WD-40 I had all over the engine. But I did not. Now, even after a thorough cleaning not only does the engine no longer look like new, but a couple of months later my alternator locked up solid.  I’m thinking that three years is all I can trust the raw water pump.

George Southern

Blessing #101

On Jul 23, 2026, at 9:55 AM, catalina <cata...@thehares.com> wrote:



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[Dhyanesh Kostka]

I have installed a temperature sensor in the exhaust elbow. If the raw water pump fails, the temperature spikes immediately, showing me that something is wrong.

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[Ernie Bubb]

Thanks to all for advice. 

Ernie

Sent from my iPad

On Jul 23, 2026, at 2:14 PM, Dhyanesh Kostka <dhyanes...@gmail.com> wrote:



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