Overheated Weirdness

[Jeff48081]

Hello all and thanks in advance.
Having a overheating issues where the port side off my mercruiser 260 is getting hotter and I noticed this when my exhaust robber boot gor so hot it melting. This boot located right below the exhaust elbow. The starboard side is fine.
Okay I replaced the boot and let the motor iidal for 20 minutes and I start seeing smoke coming from the new boot.
Now my question is what could cause this ? I'm thinking perhaps it could be a Bad Exhaust Shutter?
The boat is an older Searay..

 

[todhunter]

Idling in the trailer, or with the boat in the water?

Are you getting water flowing into and out of each exhaust manifold and elbow?

 

[alldodge]

Welcome
Happen to know the serial number of the motor?

There are a few models of the 260

 

[dubs283]

Verify raw water cooling supply. First place to check is raw water pump/impeller

Nothing weird about a melting rubber exhaust component due to lack of proper water flow

 

[Lou C]

Either water’s not getting in that manifold/elbow or not
out…
Salt water boat?

 

[kenny nunez]

Do this test without the engine running. Locate the hose that goes to the port exhaust riser, disconnect it at the thermostat housing then connect a garden hose to it. This will tell if the riser is causing the problem. The water should flow freely, if not or if the hose to the riser starts swelling up then you have found the problem. Sometimes it is possible to clear the slag out of the riser or replace it. There may be a stainless sleeve inside the exhaust opening, you will have to remove it to get to the restricted area. Then just drive it back in.

 

[Scott Danforth]

Lack of cooling water means the exhaust goes from 200f to 1100f

Burnt rubber means no cooling

 

[flashback]

The elbow may be rusted up. I had to replace mine last season for the same reason

 

[Lou C]

At the end of this season I'm pulling mine, 5 full seasons in salt water, may also wind up replacing the manifolds at the same time. No cooling problems as of yet, but......

 

[dubs283]

No cooling problems as of yet, but......

Failing exhaust manifolds start with excess temperature within the combustion chamber due to water contamination

First notable indication of such is noted with a plug burn using current setup

 

[Lou C]

My past history with the old OMC Batwings showed that there was enough corrosion to start clogging the relatively small outlets after 5-6 seasons. Even then I never had hot running problems or overheated spark plugs. The exhaust I have on it now (later OMC/Volvo 2 piece) has larger cooling passages but still you will always have the risk of clogging the outlet in the elbow or rust thru. So this fall they’re coming off…