Engine Temperature Fluctuates

J

jomo

Active member
Joined
Apr 28, 2020
Messages
28
Fluid Motion Model
C-30 S
Vessel Name
JOMO
We cruised from Shilshole down to Gig Harbor this weekend between 2100 to 2600 rpm. I noticed the engine temperature was at 185 (normal) then dropped to 170 then 165 then back to 180 and eventually back to 185. Then a couple of minutes later the engine temp dropped again to 179,178, 170 (random temps in the 70s). We were fluctuating speed to miss logs and slow down for large waves. I am not sure if the speed fluctuations can change engine temp but maybe..? I have never seen the temp fluctuate once it reaches 185 so I found this to be strange.

Any ideas on 1) Is this an issue 2) Any ideas as to why?

2017 29S Volve D4 260
 
I don't have an answer for you. But our 2018 R29 never fluctuates. Once iyt warms up to 185 it never moves until we shut it down. We often run at various speeds.
Since the temp goes down...i would suspect the thermostat rather than a clogged strainer or bad impeller. The other option could be a bad electrical connection...but speed shouldn't have an effect on that.

Sorry I couldn't be more help, but ot does sound like you have an issue.

Rocky
 
I second the thermostat. I have had them stick open and closed. Open is a bit easier to deal with.
 
We a had something similar happen a few weeks ago. We were fishing and switching helmstations back and forth and then when we left the area the temperature indicator on the VP display was fluctuating erratically. It would show 175 then drop to 165 then 140 very quickly and then maybe 175 again. So I shut down the engine and shut off the ignition tab. I waited a minute then fired it up and then it showed 185 steady as usual. So I am assuming what I did was the equivalent of rebooting a computer. In our case the temperature showing was fluctuating so fast that I knew something was wrong as there is no way for the temperature to fluctuate that fast in a Diesel engine.
 
Thanks for all the replies.

We were actually switching between the main and aft helm station because I was also checking the stuffing box to make sure it was dripping at the rate 1 drop every 20 seconds. Maybe this switching had something to do with it.

I will check the temp again this week and only use the main helm station and see if that had anything to do with it.

Otherwise, we will have someone look at the temperature sensor (this is out my comfort zone to check).
 
jomo said:
We cruised from Shilshole down to Gig Harbor this weekend between 2100 to 2600 rpm. I noticed the engine temperature was at 185 (normal) then dropped to 170 then 165 then back to 180 and eventually back to 185. Then a couple of minutes later the engine temp dropped again to 179,178, 170 (random temps in the 70s). We were fluctuating speed to miss logs and slow down for large waves. I am not sure if the speed fluctuations can change engine temp but maybe..? I have never seen the temp fluctuate once it reaches 185 so I found this to be strange.

Any ideas on 1) Is this an issue 2) Any ideas as to why?

2017 29S Volve D4 260[/quote

When was the impeller last changed out? Thermostats hardly ever fail, when was the last time you had to change one out in your car.
Click to expand...
 
The impeller was changed out when we purchased the boat a year ago (March 2019).

Based on the rapid changes in the digital temperature gauge, I doubt it is the engine. It fluctuated so fast that it couldn't have been the engine changing temperature.

I am going to check it again this weekend when we go out.
 
Had a similar problem two years ago on our 2016 R-29S. Spend 53 days in the Broughtons with no problem then 3 miles from home the temp started registering 5 to 20 degrees. Assumed it was the temperature sensor and went to Kent to order a new one. Richard said first try cleaning the connections and apply some electro light grease. The connections still looked brand new, but I did apply the electro light. Started the engine everything back to normal and two years later not a problem.
 
Had a similar problem two years ago on our 2016 R-29S. Spend 53 days in the Broughtons with no problem then 3 miles from home the temp started registering 5 to 20 degrees. Assumed it was the temperature sensor and went to Kent to order a new one. Richard said first try cleaning the connections and apply some electro light grease. The connections still looked brand new, but I did apply the electro light. Started the engine everything back to normal and two years later not a problem.
Click to expand...

Where can I find the connections to apply the electro light grease?
 
I think what he’s using is called dielectric grease. If Electro Light Grease is a brand name, I can’t find it.
 
Dielectric grease is correct. The connection is on stbd side of engine block, mid block halfway down.
 
Thanks, 1Harrison. I'll do it this weekend and let you know.
 
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