Exhaust overheat on 4.3 gxi

[saaristo]

Pulled out my boat the other day - ran it for five minutes on the hose and got really surprised. Port side exhaust manifold, riser and exhaust pipe was just warm or even rather cool as it should be. But on the starboard side, manifold and riser was uniformly warm/cool but the exhaust pipe was so hot it got me swearing when I touched it. So how's that possible? I would imagine if there is lack of waterflow or obstruction or something then also manifold and riser would overheat? But only the exhaust pipe? Any ideas?

 

[Scott Danforth]

was your boat sitting completely level? as in perfectly level?

if not, the lower manifold gets more water than the higher manifold

completely normal when boat is on a trailer

 

[Lou C]

Ok I installed the same style exhaust on my OMC Cobra replacing the old bat wings. And yes the starboard side alu exhaust pipe between the upper and lower hoses does get hotter that the port side. Port is about 100* starboard is about 135-140 depending on where you measure it. Water flow in these systems is never 100% equal on both sides. This is with a totally cleaned out thermostat housing as well. If yours hasn’t been cleaned out then that’s one thing to try the passages do get necked down by corrosion. On mine the manifolds & elbows are at about the same temp, idle 100 or so highest after coming off plane is about 125-135.

 

[saaristo]

Hmmm...measured the position now, if anything, the starboard side is actually lower. And since it is closed cooling (forgot to mention that) the thermostat doesn"t affect the waterflow in exhaust. Someghings wrong here...

 

[Lou C]

If it’s a Volvo you should have a half system

 

[saaristo]

If it’s a Volvo you should have a half system

Yup, half system, meaning the seawater goes through heat exchanger and out through exhaust.

 

[Scott Danforth]

Someghings wrong here...

see post #2

the higher manifold is always hotter, especially while on the trailer and on muffs