Port Engine Running Hot

[Thomv]

Over the weekend I was able to replace the raw water pump along with the thermostat housing and thermostat on my starboard engine. This engine was running between 190 to 200 degrees before the change. It now is running between 150 and 160 degrees. Now on to the port engine which also is running around 200 degrees. When idling the first thing I noticed is on my thermostat housing the two left side hoses are very hot while the other two hoses on the right side were both cool. The same with both of my risers, the left side is hot and the right side is cool, With this type of condition what should I look for first. Also both exhaust through the transom exhaust pipes are throwing out about the same volume of water. I did forget to check the water temperature out of both exhaust pipes. I could not attach a photo of the housing because it was too large of a file. My starboard engine developed a water leak straying both motors causing all of the rust which right now is not on the top of my to do list because of the over heating condition.

 

[Thomv]

Any ideas what I should look for under my first posting?

 

[Scott Danforth]

start with the water pump on your port engine. Then change the thermostats. are these motors fresh water cooled or raw water cooled?

 

[Thomv]

start with the water pump on your port engine. Then change the thermostats. are these motors fresh water cooled or raw water cooled?

Raw water cooled.

 

[Thomv]

On Saturday I did replace the thermostat. I also cleaned out the thermostat housing, removed any rust and repainted. After doing all of this I still am reading high on my water guage between 190 and 200 degrees while just idling once the motor warmed up. I did buy a thermo scanner and this is what I found. My water temperature out of the large water hose coming from the engine water pump to the thermostat housing was showing 148 degrees. My other three hoses from my thermostat housing was around 88 degrees. Of these three other hoses two go to each riser while the other is coming from my sea strainer. When I scanned both risers my left riser was showing 135 degrees while my right risers was 90 degrees. Water coming out of both open exhaust pipes was about the same volume with the left one warmer than the right. If my left riser has some blockage how do I check? I was thinking of disconnecting both the left and right hoses going to the risers and connect a t fitting with a water pressure gauge to see what kind of pressure reading I will get once I turn on the hose.for each riser. Does this make any sense?

 

[alldodge]

On Saturday I did replace the thermostat. I also cleaned out the thermostat housing, removed any rust and repainted. After doing all of this I still am reading high on my water guage between 190 and 200 degrees while just idling once the motor warmed up. I did buy a thermo scanner and this is what I found. My water temperature out of the large water hose coming from the engine water pump to the thermostat housing was showing 148 degrees. My other three hoses from my thermostat housing was around 88 degrees. Of these three other hoses two go to each riser while the other is coming from my sea strainer. When I scanned both risers my left riser was showing 135 degrees while my right risers was 90 degrees. Water coming out of both open exhaust pipes was about the same volume with the left one warmer than the right. If my left riser has some blockage how do I check? I was thinking of disconnecting both the left and right hoses going to the risers and connect a t fitting with a water pressure gauge to see what kind of pressure reading I will get once I turn on the hose.for each riser. Does this make any sense?

You should have 160 degree thermostats installed. Your gauge is reading 190 to 200 degrees but your inferred gauge reads temps not equal to the boats gauge reads. Your starboard engine was doing the same until the impeller and thermostat was replace, now it reads 150 to 160. If your MPI engines do not reach a minimum of 160 they will always run rich.

In short, it may be your boats gauges because your IR gun is not showing an overheat condition. One riser will always be hotter then the other, but it should be under 170 degrees or so

 

[Thomv]

This morning I decided to try and swap both temperature gauges. What I found was quite interesting. The gauge that was running hot had one of the middle wires mounted to the screw without a nut. It was just loose sitting on the screw stud. I would think this would have caused a higher than normal resistance on that connection. I still decided to swamp both of them out and also add a lock washer and nut to the missing one. I ran the problem engine for about 30 minutes and watched the temp gauge climb up to 165 and then fall back down once the thermostat opened up. It then steadied out around 165 degrees. The warmer of the two risers scanned around 110 degrees while the other was lower at around 90 degrees. Why is there some much of a difference between both risers? Is one more blocked than the other? I also ran the other engine and the switched out gauge acted the same way with no over heating condition. Do you also know at what temperature would the warning horn go off indicating and over heat condition?

 

[tank1949]

I just experience similar problem and it has happened before. Risers are the first to go or clog. I suspect due to the meeting of hot gasses and water.To touch, one riser was hotter than the other. I pulled riser and discover water passage partially restricted. I was able to insert 1/8 long drill and dislodge rust. I put back on and heat went away. I operate in salt water and alway fluish when returing, but I still have to physically (touch) and compare heat.

 

[alldodge]

This morning I decided to try and swap both temperature gauges. What I found was quite interesting. The gauge that was running hot had one of the middle wires mounted to the screw without a nut. It was just loose sitting on the screw stud. I would think this would have caused a higher than normal resistance on that connection. I still decided to swamp both of them out and also add a lock washer and nut to the missing one. I ran the problem engine for about 30 minutes and watched the temp gauge climb up to 165 and then fall back down once the thermostat opened up. It then steadied out around 165 degrees. The warmer of the two risers scanned around 110 degrees while the other was lower at around 90 degrees. Why is there some much of a difference between both risers? Is one more blocked than the other? I also ran the other engine and the switched out gauge acted the same way with no over heating condition. Do you also know at what temperature would the warning horn go off indicating and over heat condition?

It is all an issue with hydraulics and how water flows. The one riser has less restriction based on flow patterns and the other needs the water to change directions and therefore create less flow and a bit higher temps. It's all normal so for what I'm seeing this far I would chalk it up to your gauges and not the engines.

 

[Thomv]

It is all an issue with hydraulics and how water flows. The one riser has less restriction based on flow patterns and the other needs the water to change directions and therefore create less flow and a bit higher temps. It's all normal so for what I'm seeing this far I would chalk it up to your gauges and not the engines.

I agree. Thanks for the explanation about why one riser is warmer than the other.