Engine Steam

[SanJuanDreamer]

On our way to Pleasant Harbor, Wa I decided to take some temps while under way as I noticed steam about 15 to 20 feet behind exhaust. Not really abnormal for my boat but I wanted to see what was going on.
Here is what I found:
Starboard Engine at neck\temp sensor was 168 while running at 18rpm. While running at 36rpm, it read 177. The thermostat on the heat Exchanger is set to 170. The thermostat was 165 at 18rpm and 189 at 36rpm.
The exhaust riser on left was 104 and the right was 95. Not sure why so much stream.

On Port at neck\temp sensor was 160 while running at 18rpm. While running at 36rpm, it read 189. The thermostat on the heat Exchanger is set to 170. The thermostat was 158 at 18rpm and 180 at 36rpm.
The exhaust riser on left was 107 and the right was 101. Again, not sure why so much stream.

The temp gauges were not so accurate at 18rpm, but read accurately while at 36rpm.
I did temp checks on other hoses and found there was about 10degree diff between them all at 18rpm. Mainly in the range from 141 to the highest at 157. At 36rpm, add 10 degrees for those hoses.

The engines are 454xli with +1400hrs.
Anyway, something to think about.

[SanJuanDreamer]

After some thought, I noticed the part about "Starboard Engine at neck\temp sensor was 168 while running at 18rpm. While running at 36rpm, it read 177". I think I missed the mark on that one.
If the cooler water comes from the Heat Exchanger to the neck\temp sensor, then I believe that temp should be 198 on the starboard at 36rpm...using the Port engine temp checks. Seems there is a 2 degree diff between HE and neck on the port engine while at 18rpm, at 36rpm its a 9 degree diff. Based on that, I should add 9 degrees to the starboard, which now is over an acceptable level.

[km1125]

Qr Bbpost After some thought, I noticed the part about "Starboard Engine at neck\temp sensor was 168 while running at 18rpm. While running at 36rpm, it read 177". I think I missed the mark on that one.
If the cooler water comes from the Heat Exchanger to the neck\temp sensor, then I believe that temp should be 198 on the starboard at 36rpm...using the Port engine temp checks. Seems there is a 2 degree diff between HE and neck on the port engine while at 18rpm, at 36rpm its a 9 degree diff. Based on that, I should add 9 degrees to the starboard, which now is over an acceptable level.

I'm not following you.

Are the thermostats in the engine 160 degrees? You say "The thermostat on the heat Exchanger is set to 170'.. does the exchanger also have thermostats?? Usually it's just an exchanger and the thermostat in the engine is doing all the temperature regulation.

[SanJuanDreamer]

The thermostat is attached at the Heat Exchanger, away for the neck where the temp sensor is located. The neck is where one would add antifreeze.
The manual calls for a 170, so I assume that's what's in it.

[mjk1040]

Raw water impellers, cams and wear plates. Recent change of my impellers included an information sheet for the Sherwood raw water pumps and frequency of maintenance schedule. Thinking raw water flow is proportional to engine heat dispersal. After changing my impellers the amount of steam from exhaust ports was considerably less, since the pumps are 19 years old and have 600 hours on them, thinking cam and wear plate replacement is in order too. And hopefully no steam at all, since I'm not overheating per temp gauges, running 140 with 143 degree thermostats per open cooling specs.

[Viper]

Raw water pump efficiency is definitely a possibility. Restrictions in the exhaust elbows' water passages where the water exists the elbow will also cause this. After 5 years in a salt water application, this is a possibility as well. What is the current ambient water temperature? Do you have this problem all year long or just the colder part of the year?

[SanJuanDreamer]

Last weekend I went through the raw water cooling side.
On the Port HE, I found about 4 -5 tubes blocked and restriction in a few others.
On the side of the HE that's difficult to get to, the outside of the tubes had corrosion, I cleaned it up.
Went through the oil cooler and found a couple blocked by debris...wasn't expecting that.

Did the same for the Starboard too, but found little problems with that oil cooler.
So, well see what comes of it...

[mjk1040]

Thanks, that's good info. I may have to investigate the same if my issue worsens.

[SanJuanDreamer]

Update, the Port engine ran just above 160, improvement.
The Starboard had no change, still running at 177 - 178.
I guess I'll check out the raw water impeller and pump and everything in front.
It has about 90 hours on it so I was hoping that wouldn't be a cause.
BTW...these temps are running on plane at 25mph at 36rpm, idle and cruise are fine.

[mjk1040]

Is Descaling in order for the entire system???