PCM 555 Merc 496 STB EMCT OVRHT

[helladotnet]

I have a 2005 Rinker w/ dual Mercruiser 496s. I have been having an issue for a while where after running the boat for a while without beeping it starts to beep once it is back at idle. I broke down and finally purchased a Rinda scan tool and after running today and the issue occurred I found that I am getting a "STB EMCT OVRHT" error (not a PORT error, just stb). I have already replaced the back side of the raw water pump (engine flush was leaking) and replaced the impeller. This 496 has Bravo IIIs and around ~300 hours on the boat. I have had this issue for quite some time and have multiple shops look into the problem. Any help that someone can provide would be greatly appreciated.

If there is other information that would be helpful to help diagnose this issue please let me know.

I did notice that the following is listed in the "performance data" when I connected the Rinda immediacy after getting having the issue.
Port Exhst Cool Temp - 105 deg
Stbd Exhst Cool Temp - 392 deg
Manifold Air Temp - 129.2 deg
Lake/Sean Temp - 431.6 deg

Could these temp readings be correct or maybe I have an issue with the sensor?

 

[alldodge]

I have a 2005 Rinker w/ dual Mercruiser 496s. I have been having an issue for a while where after running the boat for a while without beeping it starts to beep once it is back at idle. I broke down and finally purchased a Rinda scan tool and after running today and the issue occurred I found that I am getting a "STB EMCT OVRHT" error (not a PORT error, just stb). I have already replaced the back side of the raw water pump (engine flush was leaking) and replaced the impeller. This 496 has Bravo IIIs and around ~300 hours on the boat. I have had this issue for quite some time and have multiple shops look into the problem. Any help that someone can provide would be greatly appreciated.

If there is other information that would be helpful to help diagnose this issue please let me know.

I did notice that the following is listed in the "performance data" when I connected the Rinda immediacy after getting having the issue.
Port Exhst Cool Temp - 105 deg
Stbd Exhst Cool Temp - 392 deg
Manifold Air Temp - 129.2 deg
Lake/Sean Temp - 431.6 deg

Could these temp readings be correct or maybe I have an issue with the sensor?

:welcome: to iboats

Your issue is the 392 degrees on the starboard exhaust manifold. Overheat is set for above 212 degrees.
Manual states:
Restricted or loss of water flow, or ~~Faulty seapump, or Faulty shaft log seal
Inspect for blockage or leaks in the raw water section of the engine, or Inspect seapump for excessive wear. Repair, or Inspect shaft log seal.

You have outdrives so shaft log is not relevant.

The sensor could be bad or unplugged due to dirty connection, or you could have a clogged manifold issue.

Do you run in saltwater?

 

[achris]

He's at the bottom of Lake Erie. Is that salt or fresh?

 

[helladotnet]

Thank you AllDodge for the quick response. We run in freshhwater only. Sorry for the lame question but what should I do to check to see if the manifold is clogged?

 

[camalot]

I've been help a buddy with almost the same problem, and even thou we changed the impeller it would still show overheat in the manifolds. So after some googleing it would seem that the sea pump is not the best of designs.

We had small .50mm deep grooves on the two impeller sealing faces, I machined the back face for him and we purchased a new front housing.Ran the boat last night for a hour checking the manifolds and riser with a IR gun from time to time in different conditions of running and all was good.

The pump still didn't prime to quick so need to look at that, but once primed it worked as it should..................... a long with the boat.
[h=4] [/h]

 

[achris]

Try swapping the temp sensors across. If the fault follows the sensor, you know you have a failed sensor. If it stays with the stb side, look for something else... If it is the sensor, the part number is -885342002, and they are only about $28....

 

[alldodge]

I would suggest getting the rebuild kit that comes with the stainless steel wear plate. The impeller will have a harder time wearing into stainless. Many have gone that route to stop the wear on the Gen 7 pumps.

As far as the priming, check the package of the impeller you have. This is a long shot, but there were some impellers made that were a few mm shorter then spec. Most all have been found. I'm working from memory but I seem to remember something about a green dot on the package.

 

[camalot]

I would suggest getting the rebuild kit that comes with the stainless steel wear plate. The impeller will have a harder time wearing into stainless. Many have gone that route to stop the wear on the Gen 7 pumps.

As far as the priming, check the package of the impeller you have. This is a long shot, but there were some impellers made that were a few mm shorter then spec. Most all have been found. I'm working from memory but I seem to remember something about a green dot on the package.

Yeah I think this would be the way to go fitting a repair kit with wear plates...........makes 100% sense with a warn plump. I did check the impeller length as I did read about the length problem, but we do have the correct one 50.80mm/2" but thanks for the suggestion!

Having side exit exhaust makes it easy to see the flow of water at idle, once primed there is really good flow now as before it was just a trickle.

 

[helladotnet]

Thanks to all for the information. I added a stainless wear plate this past winter thinking that was the issue. I will swap the sensors today and see if the issue occurs when I run her home tomorrow.

 

[Fun Times]

Thanks to all for the information. I added a stainless wear plate this past winter thinking that was the issue. I will swap the sensors today and see if the issue occurs when I run her home tomorrow.

Also you need to confirm the actual engine and exhaust temperatures. Using an infrared laser temperature gun would be the best and safest way of testing the temperature. Good luck.

 

[helladotnet]

I wanted to post an update of my findings after working through the tips that all of you provided. I checked out the entire stbd side from the heat exchanger to the transom and there were no blockages. I then got the boat up to temp and while having the rinda connected I started to see the temp jump (120 to 300 back to 120 then up to 400) it looked as though it was some sort of short. I followed the sensor cable back to the PCM and decided to swap PCMs from the stbd motor to the port side. After doing that I was NOT able to reproduce the issue. I then swapped the PCM back and again still wasn't able to reproduce the issue. I swapped the PCMs back one more time (stbd pcm is now on port motor and vice versa) and have ran the boat for two weekends without any issues. I am now wondering if the wiring harness on the PCM was loose and needed to be reseeded. Has anyone heard of something like this before?

 

[Fun Times]

I am now wondering if the wiring harness on the PCM was loose and needed to be reseeded. Has anyone heard of something like this before?

Sometimes for unexplained reasons that's all it takes to solve a problem. While the wire connector was out, did you inspect the wire pins for foreign objects or pins backing out of the connector?