Exhaust manifold riser temperatures

[bscheper]

I have a 1992 Merc 305 4bbl, 235 hp with a 160 degree thermostat. I noticed the other day that the right (facing rear of boat) exhaust manifold/riser temperature was much hotter than the other to the touch. I have an IR thermometer but wanted to know what would be an acceptable temperature range?

 

[alldodge]

I have a 1992 Merc 305 4bbl, 235 hp with a 160 degree thermostat. I noticed the other day that the right (facing rear of boat) exhaust manifold/riser temperature was much hotter than the other to the touch. I have an IR thermometer but wanted to know what would be an acceptable temperature range?

There is normally no issue, it's just the nature of how water flows through the channels. If you can touch it and it doesn't burn you your fine,

 

[bscheper]

It does burn my hand on the right. That is why I was curious about acceptable temp range

 

[alldodge]

Your going to find around 20 degrees hotter then the other. Now I cannot leave my hand on the riser without pain but I can touch it without getting a burn. If you get an instant burn then it is to hot

 

[HT32BSX115]

I have a 1992 Merc 305 4bbl, 235 hp with a 160 degree thermostat. I noticed the other day that the right (facing rear of boat) exhaust manifold/riser temperature was much hotter than the other to the touch. I have an IR thermometer but wanted to know what would be an acceptable temperature range?

Salt (raw) water cooled engine? If so, how old are they (both risers/manifolds)

There's also possibly check balls that regulate water flow to both sides. If the flow is weak on one side, it will run considerably hotter.

If you get an instant burn then it is to hot

Yup!

 

[bscheper]

If I touch it is not instant burn but much more then uncomfortable if I leave my hand on it. Raw water cooled and only used in fresh water. I have owned it for the last 20 years and it is 22 years old. Both risers and manifolds are original. Thats also why I wanted to know an estimated temp range expected so that I could plan for maintenance accordingly. (Would you believe 22 years old and never even needed to tune the carb and has never not started for me. I guess good winterization process, maintenance does pay off. I need to go and knock on some wood.)

 

[Bondo]

If I touch it is not instant burn but much more then uncomfortable if I leave my hand on it. Raw water cooled and only used in fresh water. I have owned it for the last 20 years and it is 22 years old. Both risers and manifolds are original. Thats also why I wanted to know an estimated temp range expected so that I could plan for maintenance accordingly. (Would you believe 22 years old and never even needed to tune the carb and has never not started for me. I guess good winterization process, maintenance does pay off. I need to go and knock on some wood.)

Ayuh,..... It oughta be well under 180°,.... It hurts to hold yer hand on 110°,.....

 

[bscheper]

Great Thanks. I will check the temp of both this weekend and post back.

 

[HT32BSX115]

22 years old. Both risers and manifolds are original.

Time to replace the risers and manifolds.......You've had a good (and lucky) run on both!

 

[bscheper]

Thanks too all. Left manifold is 160 and right is 180 just as ALLDodge said. Tks to all.

 

[DJ Jaws]

Might be time for a cleaning? That sounds a little high. Maybe there's some build-up restricting water flow. I'd pull them off and see what's going on. Could save you a headache later.