5.7L overheating on just one side?

[LoudDog]

the details: 1996 mercruiser 5.7L with alpha 1 out drive, not Fresh water cooled, and used in salt water.

Last year the the water on the right side coming out the back when flushing it was always a little warmer, but never too much warmer. Getting it ready for taking out this year, the right side is getting real hot now. after running about 15 mins steam is coming out with the water, just on the right side. Using a non-contact thermometer the temps on the cooling manifold and riser on the right side is getting to 160+ while the left side stays at or below 110.

I took the riser off and water passes though all the channels, but I never opened one of these so I have no clue what I'm looking at. there is corrosion in there, but it's not too terrible.

I'm thinking I'm going to replace the manifold and riser on that side? Could it be anything else?

Please help!!! I'm pretty good working on cars and what not, but pretty new to boats.

 

[mikeneal]

Re: 5.7L overheating on just one side?

Needs a new impeller I bet. Could be you sucked up trash and clogged something but fresh water manifolds last forever.

 

[LoudDog]

Re: 5.7L overheating on just one side?

The impeller was changed last year and it's pumping water just fine. Could it be the impeller?

Also, it's NOT freshwater cooled. I opened up the side that is getting hot and there is some corrosion in there. I don't know how much is enough to cause a problem?

Could the problem be the other side is not hot and should be? But it should not be getting hot enough where steam is coming out at the outdrive? Should it?

Thanks

 

[LoudDog]

Re: 5.7L overheating on just one side?

Also, i need to note that this is all while running in the yard off a hose. Digging around I fould one guy that said it's normal for one side to overheat when running on a hose? Is this true?

Thanks

 

[mikeneal]

Re: 5.7L overheating on just one side?

Also, i need to note that this is all while running in the yard off a hose. Digging around I fould one guy that said it's normal for one side to overheat when running on a hose? Is this true?

Thanks

Certainly not normal to "overheat" when on a hose but it is very true one side gets more water and runs cooler while on flush muffs.

 

[Dshow]

Re: 5.7L overheating on just one side?

I have a 2001 5.7L Mercruiser TBI. After running hard, I will see steam coming out the driver side exhaust outlet. You can notice a temp difference on two hoses going to the risors from the thermostat housing. I removed the thermostat housing to see if one side was restricted and both outlets to the risors were clean. Since it's been this way for a couple of years and it's not causing me any issues, I just keep an eye on it.

 

[LoudDog]

Re: 5.7L overheating on just one side?

SO I think I found the problem, it's me!

I noticed one side hotter then the other so I ran it up to 2000 rpm for a few minutes and that's when it got ugly, I got scared, and asked my question.

Running it now, just at idle, one side stays about 125, the other about 85. No big deal.

I now know I'm not suppose to go anything over idle on muffs...

Thanks!

 

[JoLin]

Re: 5.7L overheating on just one side?

SO I think I found the problem, it's me!

I noticed one side hotter then the other so I ran it up to 2000 rpm for a few minutes and that's when it got ugly, I got scared, and asked my question.

Running it now, just at idle, one side stays about 125, the other about 85. No big deal.

I now know I'm not suppose to go anything over idle on muffs...

Thanks!

The only thing that changed when you slowed it down, is the absolute temperature. I think you still need to determine if a 40-50 degree difference from side to side, is normal. No, I do not know the answer to that, but to my inexperienced eye it seems extreme.

 

[deves3000gt]

Re: 5.7L overheating on just one side?

Just out of curiosity, is the boat sitting on a tilt so the side that is heating up is higher then the other? I was have the same ting happen to my boat, the one side would get hotter then the other and the water flow would be a little less. Would also get some steam at idel. Someone on here had said they bet that side was the uphill side. It was. try putting a few boards under the tire on the "cooler" side and see if it canges anything.

 

[Fun Times]

Re: 5.7L overheating on just one side?

the details: 1996 mercruiser 5.7L with alpha 1 out drive, not Fresh water cooled, and used in salt water.

Last year the the water on the right side coming out the back when flushing it was always a little warmer, but never too much warmer. Getting it ready for taking out this year, the right side is getting real hot now. after running about 15 mins steam is coming out with the water, just on the right side. Using a non-contact thermometer the temps on the cooling manifold and riser on the right side is getting to 160+ while the left side stays at or below 110.

I took the riser off and water passes though all the channels, but I never opened one of these so I have no clue what I'm looking at. there is corrosion in there, but it's not too terrible.

I'm thinking I'm going to replace the manifold and riser on that side? Could it be anything else?

Please help!!! I'm pretty good working on cars and what not, but pretty new to boats.

Hi thought I would jump in and help give you something to look at that might help, At the thermostat housing you might have a check ball valve on a spring type rod that a lot of times will get stuck or bound up if you will. Some engines have it some do not, But if your dose then it will do what you are saying is happing, and yes one side will run a little hotter then the other that is normal on some of those engines. To fix it you could either grab the black hose tight that goes from the "thermostat housing" to the riser and and push and shove the hose right at the end of the hose right before it gose in to the thermostat housing to loosen and and brake a way any thing that might be holding it closed not letting the water flow thur, Or you could take the hose off for the first time to see what I am talking about and to make sure your system has this or not, I normal will try to clean the area up a little if I take the hose off and I shoot some WD-40 when done but that may not really do any thing It just makes me feel like I tryed to keep it freed up the best I can is all. Once you see it you will know what I am talking about of grabing it and try moving it while the engine is running then you will see the water coming out the exhaust at a better flow rate but most of the time you will never get a perfect 50/50 flow out the exhaust it will be more like a 60/40 or some times even a 70/30 on the hose flow rate that is why one side will run hotter. Also some engines will have a tube that will go from the intake manifold to the exhaust manifold for smog burn off if you will, And that tube will get too 220 plus degrees and will make the right side run hotter. If your engine dose has this system then I hope this helps you out a little, Good luck with it.

 

[cooter2506]

Re: 5.7L overheating on just one side?

Its ok to run it on the muffs at 1200 rpm for a short burst to get it warm but that is about it. Muffs dont allow enough water flow at anything above that. But if at idle you are getting those readings of 125 and 85 then you should be ok. BUT if you are seeing corrosion in the manifolds I would change them especially since you are in salt water. Only will get worse

 

[LoudDog]

Re: 5.7L overheating on just one side?

It's a gravel driveway and with the slight slope, it is the low side that is cooler and spitting out more water so that makes sense. I'm going to take it out to the lake, probably tomorrow, and make sure it's pumping good water from both sides and staying fairly evenly cooled. It's not over heating at idle and the water going to each side from the t-stat is the same temp (I love the non contact thermometer!) so I'm pretty sure the problem is just me. We'll find out tomorrow.

Thanks All! (I'll post what I find when I take it out)

 

[LoudDog]

Re: 5.7L overheating on just one side?

So I eventually took it out and tested it. That side still gets warmer then the other. I hung off the back while on plane and it looks like plenty of water is coming out and it is not overheating.

I think to start I'm going to change out the risers and see if that helps.

My theory here, flushing it in the slopped driveway, one side got flushed better then the other. Thus one side is a little more corroded/rusted then the other and the water does not flow quite as well now.

I'm crossing my fingers just replacing the risers will eliminate the problem. The manifolds do not look fun to replace as the bolts look really hard to get to and I'm sure they will not want to come off.