Mercruiser 260/alpha, seems to be running hot.

[holorinhal]

81 mercruiser 260/alpha, with EMI thunder exhaust, SS risers. 160* thermostat.
So the temp gauge reads from 160-175 ish when running at speed, then creeps up to around 210, when i come down to an idle or flat wake.

A couple weeks ago, i had two sections of exhaust water boot, melt and get holes in them, in the lower section at the exhaust tip and upper down tube, on the starboard side.

i can hold my hand on the very top of the riser for a good while, but as i go further stern ward and down to the exhaust tip, it gets quite a bit hotter.
i can hold my hand under the exiting water for only a few couple of seconds.

i have used a laser temp gun and shot the temps on top of the risers and various other spots.
the top of the risers read about 97*, the lower portion of the exhaust tubes read quite a bit hotter and the block and heads read around 180 or less, if i remember correctly.
The wet exhaust hose or boots are about 5 years old.

is any of this out of the ordinary? Does any one have any ideas asto the issue?
Thanks

 

[holorinhal]

Raw water system, Fresh water only.
had an exhaust leak on port side? Any thing to do with heating?
pulled riser and manifold yoday. Fixed exhaust leak.
riser joint looked good no corrosion, to speak of.
will do starboard side tomorrow to change exhaust gasket.

 

[Bondo]

Ayuh,..... Sounds like a serious lack of water Flow,......

 

[Scott Danforth]

81 mercruiser 260/alpha, with EMI thunder exhaust, SS risers. 160* thermostat.
So the temp gauge reads from 160-175 ish when running at speed, then creeps up to around 210,

you have a lack of flow issue, or a no flow issue.

A couple weeks ago, i had two sections of exhaust water boot, melt and get holes in them, in the lower section at the exhaust tip and upper down tube, on the starboard side.

without water flow, the rubber parts that have a max temp of 250 F see 1000 degree exhaust temps.

the burned exhaust indicates no water flow

i have used a laser temp gun and shot the temps on top of the risers and various other spots.
the top of the risers read about 97*, the lower portion of the exhaust tubes read quite a bit hotter and the block and heads read around 180 or less, if i remember correctly.
The wet exhaust hose or boots are about 5 years old.

and when was your raw water pump serviced? that is a replace every few year sort of thing

Does any one have any ideas asto the issue?

you have no water flow - start at the raw water pump