5.7 EFI running hotter on starboard exhaust

[Tunabass]

I removed and inspected the water pump and impeller expecting to find a bad impeller. But it was in great shape. Normally, engine runs around 160 degrees then when thermostat opens it drops to 120. The other day it was running around 180 until thermostat opened dropping it to 160 but no lower. I get it home and run on the hose and the starboard exhaust water is noticeably hotter then port. Starboard riser is also about 40 degree warmer then port. Besides thermostat which is my next check what else should I be looking at? Manifolds and risers were replaced about 3 years ago. It’s all raw water cooled. I doubt it’s the thermostat as I would assume both sides would be running warm. Open to any ideas. Thank you. Serial number of engine. OLO12923

 

[alldodge]

With a 160* thermostat the motor should stay right at 160*, it should not lower to 120*.
Start by using a IR temp gun and verify the of the thermostat housing is the same temp that your gauge is showing.

On manifold will most always be hotter the then other and more so on a hose, because the hose cannot supply the same amount of water that sitting in the water will.

If the manifold will not instantly burn your hand, then its ok for now

If it is getting hot, place a short piece of clear hose between the water intake hose and the thermostat housing. When it the water there should be no bubbles

 

[Tunabass]

I have a IR gun and will report after I attach water pump again. It’s always run up to about 160 then drops to 120 which is why I noticed something was up when I saw it stay between 160-180. Also usually both water exhaust temps are about the same. Now they are not. I’ll report back with temps later today. Thank you.

 

[Tunabass]

I have a IR gun and will report after I attach water pump again. It’s always run up to about 160 then drops to 120 which is why I noticed something was up when I saw it stay between 160-180. Also usually both water exhaust temps are about the same. Now they are not. I’ll report back with temps later today. Thank you.

Ok the engine is running right now for 15 minutes on the hose. Temp gauge is doing what it use to and goes to 160 then back to 120 then back to 160 over the course of about 20-30 seconds. IR gun shows thermostat housing no warmer then 106 even when gauge shows 160. Stbd manifold is warmer then port but no where near burn my hand. Starboard manifold is 86 and port is 63. Starboard exhaust temp is occasionally warmer then port. But nowhere near as hot as the other day. Sometimes the gauge stays near 120 for a minute or so and other times it goes between 120 then up to 160 and back down again in 20 seconds. Right now it’s holding at 160 for 30 seconds then drops.

 

[alldodge]

Think your good so far as temp
Being on a hose cal cause things to work slower. That said, none of my boats have ever done (or at least I have never noticed) what yours is doing

 

[Tunabass]

Think your good so far as temp
Being on a hose cal cause things to work slower. That said, none of my boats have ever done (or at least I have never noticed) what yours is doing

It’s weird it’s back to “normal” as far as I know it. The other day in the hose after I came in noticing above avg “normal” temps I put it on the hose and could sea steam coming from starboard exhaust from outdrive but port was cold. Now after removing and reinstalling the pump and putting a new belt on its back to what I consider normal. I wonder if I just sucked up some seaweed or something. As of now it’s normal after 30 minutes on the hose so I’ll do a in water test this weekend.

 

[Tunabass]

On the water right now and temp gauge is showing 160-180 again. It almost sounds like a bearing rattle a little but not super noticeable. 80 degrees on port manifold and 100 on starboard. Very front of thermostat is 125. Any ideas?

 

[Tunabass]

Big center top pulley housing is leaking. I ran it up to full turtle and temp dropped after a minute of running to 120. Then started to spike. Immediately brought to neutral and found water leaking out of top center pulley housing. What does this mean?? Limping in at clutch. Just a trickle and temp is staying ok. Pump is keeping up. Only one mile from ramp.

 

[alldodge]

Should take the reading where the sender is. The top of the housing has constant raw water going passed

 

[Tunabass]

First pic is the pulley that is attached to the housing that is leaking. The second pic is if the housing. When I felt the underside of the housing I could feel and remove a piece of the gasket between the housing and where it mounts to the engine. What is the housing called? I need to remove it and probably replace the gasket and inspect whatever it is called. Thank you.

 

[alldodge]

That is the circulating water pump item 10, gaskets item 11..
I most cases the pump needs replacing

https://www.mercruiserparts.com/bam/subassembly/31844/2704/200

 

[Jtom7]

Ok the engine is running right now for 15 minutes on the hose. Temp gauge is doing what it use to and goes to 160 then back to 120 then back to 160 over the course of about 20-30 seconds. IR gun shows thermostat housing no warmer then 106 even when gauge shows 160. Stbd manifold is warmer then port but no where near burn my hand. Starboard manifold is 86 and port is 63. Starboard exhaust temp is occasionally warmer then port. But nowhere near as hot as the other day. Sometimes the gauge stays near 120 for a minute or so and other times it goes between 120 then up to 160 and back down again in 20 seconds. Right now it’s holding at 160 for 30 seconds then drops.

I have a 1995 Mercruiser 5.7 carb model and Ive noticed starboard side is hotter than the port. Starboard has never gotten too hot to touch and things have been fine for me. my temp gauge runs around 140 though. Once Ive been running for a while both sides tend to even out temp wise to the touch. IDK if that helps any

 

[Lou C]

What your stat seems to be doing is sticking open (120*) then not opening fast enough or far enough (180* is too hot). Get a new stat test it in a pot of water and install a new circulating pump.

 

[Tunabass]

So when I removed the old circulation pump I could here some severe rattling. Installed the new one (test tomorrow on the hose) and opened up the old one and this is what I found. The center shaft sheered at some point.

 

[alldodge]

Good deal

 

[Scott06]

So when I removed the old circulation pump I could here some severe rattling. Installed the new one (test tomorrow on the hose) and opened up the old one and this is what I found. The center shaft sheered at some point.

Always the simple stuff. should be ok now did you replace the thermostat while you were in there ?

 

[Tunabass]

On the hose it acts normal after replacing water circ pump. In the water it runs hot on starboard still. Going to get new thermostat kit now. Short of that working it’s gotta be a blockage in the hose or manifold right?

 

[Scott06]

On the hose it acts normal after replacing water circ pump. In the water it runs hot on starboard still. Going to get new thermostat kit now. Short of that working it’s gotta be a blockage in the hose or manifold right?

its not unusual for one side to be hotter 30-40 deg than the other. I have never checked mine with a IR thermometer but others may know what the range is. I suspect if you can touch it for a second or two your ok.

 

[Tunabass]

The thing is it never use to do that. Even last week then the circ pump failed. There has to be an issue.

 

[Tunabass]

Just tested the old thermostat in a pot of water and my IR temp gun and it appears to start to open at 175 and fully open at 190. No movement at all at 160-174. Is that right?