Starboard riser running hot

[Toppozinim]

I have a 2000 model Mercruiser 4.3L Alpha I gen2 and cannot get my starboard riser to cool down. I changed the impeller twice, all seems well there. There seems to be good volume coming out of both sides of the discharge ports. I have removed the risers on both sides and do not see any obstructions. I have replaced the exhaust flappers and thermostat and yet my starboard riser keeps getting hot to the point of reaching 185F. Then I shut the engine down because something is certainly not right. Meanwhile, the port riser runs a constant 95f. Interestingly, the engine itself does not seem to warm up at all. The temp, (taken with IR gun) reads around 120 - 128F and remains there. Not sure if there is a connection between the two conditions but any advice anyone may have would be appreciated. I also tried running the engine both with the muffs and in a barrel...no change. I am at a loss as where to go from here. Seems no mater what I try it does not bring my starboard riser temp down. Grateful for any suggestions or thoughts.
Mike T.

 

[Bondo]

Ayuh,.... Welcome Aboard,..... Risers never run the same temps on both sides,.....
Is the motor dead level,..?? tip slightly it to the starboard side,.....
It sounds to me, that yer chasing a ghost,....

 

[1985 Century Mustang]

Deleted previous message. Just read that you removed your riser and checked it. They do get clogged up w rust. I know mine was really bad. I wonder if you might have a bad/faulty water pump, not impeller, but the water pump itself. There could be a water flow restriction in the system somewhere too.

 

[Toppozinim]

Deleted previous message. Just read that you removed your riser and checked it. They do get clogged up w rust. I know mine was really bad. I wonder if you might have a bad/faulty water pump, not impeller, but the water pump itself. There could be a water flow restriction in the system somewhere too.

Thanks for the quick response. I sometimes wonder the if I am chasing ghosts as well. I might just put it in the water and go for a spin to see what happens. Not sure about the engine temp either....very confusing why the engine temp will not exceed 130f yet the starboard riser runs over 180. As for the water pump, both sides seem to be spitting out the same volume of water yet the port side is only about 90+f. Anyway, thanks for the input. I will keep poking away at it. Cheers.

 

[1985 Century Mustang]

Thanks for the quick response. I sometimes wonder the if I am chasing ghosts as well. I might just put it in the water and go for a spin to see what happens. Not sure about the engine temp either....very confusing why the engine temp will not exceed 130f yet the starboard riser runs over 180. As for the water pump, both sides seem to be spitting out the same volume of water yet the port side is only about 90+f. Anyway, thanks for the input. I will keep poking away at it. Cheers.

Yeah I'd put it in the water and run it too. Maybe the pressure from the lake/ocean will be a better outcome. You won't know till u try it.

 

[1985 Century Mustang]

@Toppozinim You may want to read this thread and the other one I just posted. Some really good info here. Especially about the broken impeller.

https://www.thehulltruth.com/boating-forum/767673-why-one-riser-hotter-then-other.html

Stbd Riser hotter than Port

Scenario: 5.7 EFI Merc seawater cooled, while underway comparing the STBD riser to the Port riser shows a signifigant difference in temperature. The STBD side is almost too hot to keep your hand on it, while the port side is much cooler - just warm. I have done countless research and talked...

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