4.3 - Hot Starboard Side Exhaust Manifold

[blay127]

Serial No. - 0M059613
'98 mercruiser 4.3 with thunderbolt V ignition, one-piece exhaust manifolds

Was out for a cruise yesterday evening and after coming down off a full throttle run for about 30 seconds and then idleing a while, i wanted to check the exhaust manifolds to see if they were hot, just out of curiousity. I noticed that the starboard side was much hotter than the port side. I could only touch it for a second or two, whereas the port side i could rest my hand on for as long as i'd like. This was my first time to check them, so i dont know if this is a recent issue or if its been ongoing. but i dont know if this is a problem or not.

I had just replaced the ignition coil, dist cap & rotor, and all plug wires. The motor has about 25 hours on it, the original was replaced last spring.

I wouldnt think this is normal, so what could i start looking at? Thanks in advance

 

[Bondo]

Re: 4.3 - Hot Starboard Side Exhaust Manifold

Serial No. - 0M059613
'98 mercruiser 4.3 with thunderbolt V ignition, one-piece exhaust manifolds

Was out for a cruise yesterday evening and after coming down off a full throttle run for about 30 seconds and then idleing a while, i wanted to check the exhaust manifolds to see if they were hot, just out of curiousity. I noticed that the starboard side was much hotter than the port side. I could only touch it for a second or two, whereas the port side i could rest my hand on for as long as i'd like. This was my first time to check them, so i dont know if this is a recent issue or if its been ongoing. but i dont know if this is a problem or not.

I had just replaced the ignition coil, dist cap & rotor, and all plug wires. The motor has about 25 hours on it, the original was replaced last spring.

I wouldnt think this is normal, so what could i start looking at? Thanks in advance

Ayuh,... Welcome Aboard,.... While riser temps are rarely to never the same,...

Those manifolds are Junk, 'n were the day they came from the foundry,...

Find a conversion kit to go to 2 piece, manifolds, 'n risers, while you've still got a runnin' motor to bolt 'em too...

Those things have a long history of hydro-lockin' motors, 'n turnin' 'em into an Anchor...

 

[blay127]

Re: 4.3 - Hot Starboard Side Exhaust Manifold

Thanks Bond-O, I am well aware of the hazards these manifolds present and will be changing them out this winter.

Also, forgot to mention, the starboard side manifold (the one thats hotter), leaks a little bit from the elbow on the bottom side. I'm thinking that could be taking some flow away from the rest of the manifold and causing it to heat up more. thoughts?

 

[Nivekt]

Re: 4.3 - Hot Starboard Side Exhaust Manifold

Perhaps the starboard side manifold is clogged up with rust and doesnt flow as well. Maybe this build up of water pressure in that manifold is also whats causing the leak.

 

[cliffblue]

Re: 4.3 - Hot Starboard Side Exhaust Manifold

June 17th, 2012, 02:13 AM #18
chcliffb
[OP] chcliffb is online now
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Join Date
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Default Re: 2001 4.3L Alpha 1 - one exhaust manifold is hot and she shakes in gear. (Answers)

Ok, the manifold temp difference appears to have been caused by the right hose from the stat housing to the manifold having more bends than the left one and it being too long at the stat housing end causing it to crimp slightly in the first bend. I trimmed an inch or so off it and now the right manifold is still warmer than the left, but only slightly. The shutters still look new. The prop hub gave it up on the lake and it's replacement is a lot smoother. I have an off-idle shake and stumble that I'm 90% sure is engine. I will start another thread for it if I can't find the cause. Thanks to everyone. Cliff

1542 War Eagle Camo Duck slayer with a 25HP Mercury
21' Suntracker Party Deck with a 4.3L 190HP I/O