Exhaust Manifold and Riser - HOT

[OutforFun]

Wanting to know how hot does the exhaust manifold typically get when the engine is on and just idling on the dock. The temp gauge indicates its normal so not sure if this is broken or not but the exhaust manifold when touching after 5-10mins gets really hot to touch. I have replaced the impeller recently and the manifold was replaced back in 2019. I have the Volvo Penta 50GXiC-J engine. Serial # 3869351. Local mechanic took a look and said that the temp is (moderate). Don't know what that means but is this normal? When is it a problem? What other warning signs I should be looking out for? The reason is, I keep getting check engine light and warning beeps periodically now. Very annoying.

 

[alldodge]

It's normal idling or on a hose, pump just isn't moving enough water. The difference between pretty warm and hot is just a few degrees to the touch. One side will always be hotter then the other also, just the way the motor works

 

[Horigan]

I would get a $25 IR temp gun and measure it. Mine never get much above 120F. If either of yours are much more than that, I would pull the riser and see how much corrosion exists.

Last year mine went quickly from mildly warmer to so hot I could smell the large rubber hose smoking on a WOT run. I turned off the engine, but the resulting heat, steam, and contraction pulled a bunch of water into my engine. Found lots of corrosion in the risers. The risers were only 4-5 years old and I had been running the engine in fresh water after every salt water outing, but only at idle. Now when I rinse the engine (at a fresh water ramp), I run the engine up to 2000 rpm to ensure good fresh water flow through the exhaust manifold and risers.

 

[Donald0039]

What year? I agree get a IR temp gun. The engine temperature gauge is measuring the temp of the cooling system in the engine. Remember the engine has a impeller for raw water and a water pump that recirculates the water through the engine.

Closed cooling?

If it's a engine that you can plug a scanner into you can get the temp of the engine, each exhaust manifold and each exhaust riser. Consider a Diacom to access the engine diagnostics.

You may need to buy gaskets and pull the exhaust manifolds and risers. Could have been poor install of exhaust manifolds or risers. Too much gasket sealer blocking passages.

Once it's resolved get baseline temp readings with IR temp gun and write down for future comparison.

 

[Lou C]

Yep get the IR temp gun. I have Volvo style manifolds on my OMC. Idle is approx 95-100 (barely warm) after coming off plane the hottest they get is 125-135. If they get hotter by a significant margin I’d look at the impeller and/or exhaust elbows.