Indmar Tube-in-tube headers

[Dustinb702]

I have a 2015 23 lsv with indmar tube style headers. Noticed port side cat is about 50 degrees hotter than starboard. All tubes are normal temp coming from head, but one port side tube is a lot hotter than all other tubes when it meets the cat. Pulled o2 sensor noticed both on port have build up "one more than the other". Also Noticed slightly less water coming from port side exhaust when running off of hose. Boat is not over heating just noticed i can hold hand on starboard cat just fine but can only hold hand on port side for 2 or 3 seconds because of heat. Boat has 506 hrs. Any ideas? Thanks.

[UWSkier]

Can't recall the applicable years but there is a replumbing kit for some model year monsoons. Might be worth looking into. 

[csleaver]

You probably have a Monsoon 409 / L96 6.0 liter engine or the LS3 if you have tube style exhaust.  The replumb ETX exhaust kit were for 5.7L engines prior to 2012, so it likely will not apply to your engine.  There may be debris stuck in the exhaust, but it will be difficult to verify that.  

You may want to check the thermostat housing and hoses that send sea water to the exhaust manifolds or the water distribution tube and hoses below the manifolds for a leak or obstruction.

A worn impeller could cause a similar issue.

Edited September 7, 2021 by csleaver

[Dustinb702]

2 hours ago, csleaver said:

You probably have a Monsoon 409 / L96 6.0 liter engine or the LS3 if you have tube style exhaust.  The replumb ETX exhaust kit were for 5.7L engines prior to 2012, so it likely will not apply to your engine.  There may be debris stuck in the exhaust, but it will be difficult to verify that.  

You may want to check the thermostat housing and hoses that send sea water to the exhaust manifolds or the water distribution tube and hoses below the manifolds for a leak or obstruction.

A worn impeller could cause a similar issue.

Yes, I do have the indmar monsoon 409 l96 6.0l. Fresh impeller and transcooler is clean. I will check out the thermostat housing and hoses. I was beginning to think there was debris in exhaust because only one tube is really hot. Thanks for the replies guys.