My 496 engine running hot

[Dewayne Riley]

I have a 2006 searay sundancer with the 496 engine. My temperature is exceeding normal conditions which triggers my check engine alarm. If I run it over 3400 rpms the alarm will go off with 5-6 minutes. The temp at that point is about 190-194. I can shut it down to and idle and it will stop the alarm as the temp goes back below 190. I just replaced the impeller and it didn’t seem to help. Any thoughts on what it could be?

 

[Strecker25]

I have a 2006 searay sundancer with the 496 engine. My temperature is exceeding normal conditions which triggers my check engine alarm. If I run it over 3400 rpms the alarm will go off with 5-6 minutes. The temp at that point is about 190-194. I can shut it down to and idle and it will stop the alarm as the temp goes back below 190. I just replaced the impeller and it didn’t seem to help. Any thoughts on what it could be?

Are you in salt water? Are the manifolds and risers original? Your engine block should be fresh water (antifreeze) cooled, but the exhaust components are a wear item and need replacing as the rust and scale will build up and restrict cooling flow. It often shows itself at higher RPM's because the water flow can't dissipate the heat quickly enough

A laser temp gun can be of help to find if the risers are running too hot.

 

[KevinC]

Could be a blockage upstream from the pumps were any parts of the impellers missing? Also if you have smartcraft what does the water pressure show for the raw water? I had an overheating problem at the beginning of the season on my 8.1s that was related loose and worn belts. Never really overheated but it would have if I let it go - it was part of my beginning of the season check list.

-Kevin

 

[Dewayne Riley]

Are you in salt water? Are the manifolds and risers original? Your engine block should be fresh water (antifreeze) cooled, but the exhaust components are a wear item and need replacing as the rust and scale will build up and restrict cooling flow. It often shows itself at higher RPM's because the water flow can't dissipate the heat quickly enough

A laser temp gun can be of help to find if the risers are running too hot.

I’m running in freshwater and I do know that one of my risers is hotter than the other.

 

[Dewayne Riley]

I’m running in freshwater and I do know that one of my risers is hotter than the other.

 

[Dewayne Riley]

Could be a blockage upstream from the pumps were any parts of the impellers missing? Also if you have smartcraft what does the water pressure show for the raw water? I had an overheating problem at the beginning of the season on my 8.1s that was related loose and worn belts. Never really overheated but it would have if I let it go - it was part of my beginning of the season check list.

-Kevin

 

[Dewayne Riley]

I found that the impeller was actually good. I replaced it anyway. So it didn’t help at all.

 

[scoflaw]

I found that the impeller was actually good. I replaced it anyway. So it didn’t help at all.

Was it a salt water boat ?
What condition was the brass pump in ? Known problem.
Did you backflush the raw water side ?

 

[paulswagelock]

I have found that a 496 run on the flush port can melt the plastic insert in the b3 drive and cause an inlet restriction.

What drive? What is your water pressure?

 

[KevinC]

Do you have a single engine or twin? I believe the 280s at that time had twins - if so it this only one engine or both? Did this just start to happen or have the engine temps slowly been rising?

Also - check the serpentine belt routing (as well as tension). I had this issue a long time ago on my 260DA when I accidentally mis-routed the belt. The temps were fine near idle however on acceleration the belt started slipping because there was not enough catching one the raw water pump.

-Kevin

 

[skibum]

Follow the water inlet hose from the seawater pump all the way back to where it connects to the transom water inlet housing. Remove the 2 bolts holding that housing to the transom assembly. Look at the end of the rubber tube that is under the housing. See if it looks clogged up and corroded. It could be that you have a relatively common problem called Bravoitis.

 

[Strecker25]

Follow the water inlet hose from the seawater pump all the way back to where it connects to the transom water inlet housing. Remove the 2 bolts holding that housing to the transom assembly. Look at the end of the rubber tube that is under the housing. See if it looks clogged up and corroded. It could be that you have a relatively common problem called Bravoitis.

Just to clarify, I think you would be recommending he do this out of the water? I have to imagine the transom inlet is submerged. Hate to see him sink the boat

 

[skibum]

That's how I checked mine. He might be a little more adventurous than I am, though.