5.7 Exhaust Manifold Temp Difference

[PezzDSpenser]

5.7 OMC King Cobra, RWC, 361 hrs

At the end of last season I did a complete impeller and housing replacement (found the metal sleeve had rotated and was blocking water flow). I replaced the thermostat also. This season I notice a drastic temp difference on the exhaust manifolds (checking with infrared thermometer). 160 deg. thermostat. The starboard side has consistent temps at each cylinder. The port side has one cylinder (first in line at water input) that is easily 20-30 degrees higher. The cylinders behind it (in water flow direction) have lower temps. Both riser temps are the same withing 10 deg. Thermostat housing has a clean pass through for water ( I pulled, drilled out and cleaned rust) Hose to port side exhaust manifold is clear (temps hold well here too). Exhaust flapper is solid and in place. My guess id something may have come off the old impeller (tossed it last year so I don't have it to inspect) and way be clogging up the water channel for the first cylinder in line. Thoughts or an re-assurance would be appreciated.

Thanks!

Oh, and every boater should have an infrared thermometer on hand.

 

[alldodge]

Howdy

There will always be differences from one side to the other. If checking on a hose, the differences can be ever greater. Was the boat in the water or the hose?

 

[PezzDSpenser]

Sorry about delay AllDodge. I never got an email alerting me of this post. The bout is in the water. Like I mentioned the port side has consistent temps. The Starboard side gets hot at the first cylinder and then drops considerably as you go aft. Which would make sense with the "least resistance" path for the water flow. The water blowing by the first exhaust channel, feeding the last channel first and then working itself back to the first. I have every reason to believe I'm getting adequate flow from the impeller because the block and port side temps are all consistent. Even the hose to the exhaust manifold temp seems fine.

 

[alldodge]

Being in the water there should be ore flow then the hose. So long as its not getting so hot to burn when touched (still may not be able to keep hand on) you should be good.

 

[Silverbullet555]

These threads come up regularly for variations in temp. Many say it's normal. Yes, some variability is normal. But, higher temps around 1 cylinder would concern me. The other thing is when it changes.

If this is a new thing, then something changed in the water flow or in the engine and that should be investigated.

I would drain the block and use a bent wire to see if you can free up some of the sediment or debris in the block.

 

[PezzDSpenser]

Yes, being one cylinder is odd. I was told to check the plug. It may be a different brand and run hotter or even that it my not be tight and can't dissipate the heat. Going to check that out and re-check the block temp at that cylinder. I did pull off the hose and cap on the exhaust manifold cooling rail. It a straight open hole through, no blockage but I can't tell if the first channel going up is blocked.