overheating question

[brian4321]

Hi I have a 2000 5.0 alpha gen two that is seawater cooled. It normally runs at a steady 175 but over the past 2-3 months my temp has slowly risen now runs 180-185 and I've seen it spike up to 195 ...the impeller in the lower unit was replaced a month ago and the thermostat was replaced 2 years ago..one more thing is my port side exhaust elbow is cool enough I can comfortably lay my hand on it but the starboard elbow is too hot to keep my hand on for longer than 5 seconds or so...any advice would be appreciated, thanks

 

[Bt Doctur]

do yourself a favor and put a 140 Deg thermostat in it.Clogged up risers will do that. when were they replaced last?

 

[brian4321]

OK thanks I'll do that...as far as when the risers were replaced last, I don't know . I've only had the boat two years ...is there a way to flush them or do I just need to replace them? Also is it normal for one side to be hotter than the other side?

 

[brian4321]

Sorry for all the rookie questions but can I use an automotive t stat?

 

[Bt Doctur]

I doubt you will find a stat at 140 for an auto application, you would need to remove the riser to inspect it. post some pics for evaluation

 

[brian4321]

OK thanks doctur I'll do that next time I have a chance to work on it

 

[brian4321]

OK so I checked the power steering cooler, its clean. Then I removed the riser that was getting hot...it has some buildup in it but not a lot . I'll post some pics and see what you guys think. Next step is to get a 140* thermostat ordered.

 

[brian4321]

Ok sorry but it won't let me upload any pictures but there is very little buildup in the water passages so I think I'll just clean it up and out it back on. Is there anything else that would be causing one side to get so hot?

 

[nateo]

I spent a bunch of timing troubleshooting overheat issue recently only to discover the gauge and or sending unit was wrong. Picked up a IR thermometer at harbor freight and discovered temp was right were it should be. At it at stat housing. Experienced exact same temps you're describing. $30 well spent.

 

[brian4321]

I ordered one and it should be arriving today so I'll check that out too..

 

[brian4321]

I'm having a problem finding a 140* thermostat for my engine. Every time i search according to my serial number the only thing i find is 160* t stats...Maybe I'm not looking in the right places? Engine SN is OL617778... If anyone could point me in the right direction it would be greatly appreciated

 

[Bt Doctur]

sierra 18-3646 . you will sacrifice a bit of fuel economy but gain a precious few seconds to spot a overheat condition. It is not the build up its the clogged exit ports that stop the water. This link shows the cutaways of risers . you see the small areas the water must exit. once they clog ,water cant get out and you run hot.
.http://www.michel-christen.com/ExhaustElbows.pdf

 

[brian4321]

Thanks for the part number and the link...I'll be sure to check that out before I put it back on

 

[brian4321]

I still can't upload any pictures but the exit ports are clean as well...I took the riser to my mechanic and he said it looks good...could a bad circulating pump cause one side to run cool but the other side to run hot?

 

[nateo]

When you run it on muffs is there water coming out of both ports? When I was troubleshooting same temp problem on my 5.0 I changed impeller, removed and tested thermostat. Removed all hoses and checked for obstructions. Checked for any signs of kinking. Bought a IR temp gun and aimed it thermostat 162 degrees steady. My temp would warm up to 160 initially but then slowly climb to 170, 180 and as high as 195 or so. 162 degrees on thermostat housing, other parts of engine were much cooler then that. I see you've spent some time troubleshooting this. You may want to consider parting with that $30 on a temp if you want to chase this further.

 

[nateo]

gauges and sending units go bad unfortunately.

 

[brian4321]

Thanks for the reply nateo... I did buy a temp gun ... So I replaced t stat with a 140* and checked all hoses for blockage and removed the riser that was getting hot...everything looked good but cleaned it anyway.... So took it to the lake tonight and ran it, according to temp gun , t stat was at 150,starboard riser 160,port riser 135...my temp gauge is obviously off... My only concern is the small copper line running from my starboard manifold to the top center of the engine was 220*...I'm a rookie and don't know what this line is so can anyone tell me what it is and if it's supposed to get that hot? Thanks

 

[brian4321]

I think I figured out what it is..exhaust vent tube? Runs from starboard exhaust manifold to the intake manifold... Is that what it is and is it supposed to run at 220*?

 

[Bondo]

Ayuh,.... It carries exhaust, Yes, it gets very Hot,....

 

[brian4321]

Thanks for all the help guys