Catalyst engine riser temperature

[BillK2632]

My Cobalt has a Volvo Penta V8-300 (GM 5.7), it's a 2014 and has catalytic converters in the risers. I have also gone by the old school thought that risers temp should be 110-120deg and you can generally lay your hand on them - my old Mercruiser they were down right cool sometimes, but those were not catalyst engines. My Volvo Penta, the risers run a good bit hotter, not burning hot, but hot to the touch - 135-140deg at idle - engine temp 160. I am assuming risers with a catalytic converter run hotter?

 

[Scott215]

I would assume so. Mine don't run dead cold on my boat but I can keep my hand on them

 

[techmitch]

Cat. conv.'s need to get up to 600 - 1200 degrees f. to be efficient.

 

[Scott215]

Definitely more heat with cats

 

[stg099]

I can agree with the above. My previous raw water cooled 4.3s were warm to the touch at the risers. My current closed cooled 8.2l with catalysts run far hotter due to the cats needing to be a higher temp to be efficient.

 

[BillK2632]

I can agree with the above. My previous raw water cooled 4.3s were warm to the touch at the risers. My current closed cooled 8.2l with catalysts run far hotter due to the cats needing to be a higher temp to be efficient.

That's what I figured and what I am seeing -- my old 4.3 (non cat) was not hot at all, could hold my hand on them indefinitely. My VP with Cats is hot, not burning hot, but hot.

 

[bfernald0]

Same. Frankly, hot enough to burn I think if you left your skin on there.

Incidentally, Mercury recommends running the things at idle when you get back to the dock for 5-10 minutes just to cool the cats down before shut off. Otherwise, you flash the water to steam and leave more scale in the manifolds. You run out of fuel with one of these while running, and you risk melting the cats because you lose cooling.