wet exhaust hose burnt through

[BoatingTimbo]

Out this weekend the wet exhaust hose off one of the elbows burst on port engine and all along the nearly 4 feet of hose was bubbled from from the heat.

The hose is different from the other 3 so not sure if it was replaced because of poor water flow on that side or is just the last to be replaced over the years. It felt soft and i debated changing it but wasn't sure what too soft was?

two questions:
1. replacing the wet exhaust hose; are they all standard hoses? my engines are '85 crusader 350's. Also should i just replace all 4 hoses?

2. I'm going to get an IR heat gun to understand temp of all four elbows. If i have poor water flow and the elbow is overheating what temp will it read? what are normal ranges?

engines are running at normal operatin temp.

Any help is greatly appreciated. Thanks in advance.

 

[CaptainKickback]

Re: wet exhaust hose burnt through

I had mine actually catch on fire. When I came off plane, the up and down movement of the boat in the waves forced enough water back up the hose to put the fire out.

But the problem wasn't the hose, or even the elbow. It was the manifold. Replaced manifolds on both engines (and the elbows too because they were very corroded). Also installed a fresh water flushing system on each boat at that time.

I used the boat in salt water and kept it at a dock (could not flush). The manifolds were 3 years old when the fire occurred. And I had replaced water pumps several times. Since I started flushing, I didn't have any problems with manifold, elbows, water pumps etc. in the next 7 years that I owned the boat.

Bottom line, you probably need manifolds.

Sea ya...

 

[BoatingTimbo]

Re: wet exhaust hose burnt through

hmmm, ok. when checking the temp what kind of readings should i see in normal range at manifold vs. elbow?

 

[sdowney717]

Re: wet exhaust hose burnt through

far below the boiling point is normal.
Maybe 140F

I modified my risers so the glycol flows thru them as well as the manifolds.

I brazed on a large bronze nipple to the output and attached a stainless water injection tube.
Then blocked the single water outflow on the riser.
My risers were easy to reconfigure.

Now going on 15 years with the same ones in salt water.

 

[BoatingTimbo]

Re: wet exhaust hose burnt through

Ok so at riser around 140F and normal at manifold will be closer to actual engine temp at 160F or so? Or will Manifold be hotter? I'll check temps from manifold through riser but would love to know normal ranges.

this way i'll understand if i need to replace manifold as well?

 

[sdowney717]

Re: wet exhaust hose burnt through

Normal here does not exist, going to vary between engine and loading.
Why not do a flow test, take a decent pressured hose and see how they flow and if the water pressure is let out or retained by rust.
My temps are guesstimates, my manifolds and risers are all part of the fresh water cooling circuit.
The other boat when I used to run with raw water thru manifolds and risers were cooler.

Either way too hot to hold a hand on them very long, certainly way below boiling point.
Never the hoses get soft from too much water temperature and no steam exiting the boat exhaust at rear.

If the manifolds are part of the fresh water cooling then they should be close to engine thermostat range. They may vary from the block temp depending on if water flows direct from heat exchanger to manifold to block or heat exchanger to block - heads - manifold

On my engines, the recirculating pump takes cooled water from heat exchanger and pumps into risers, then exhaust manifolds then heads-block then intake manifold then out the thermostat and back to heat exchanger. So my risers run cooler than the exhaust manifolds.

 

[Bondo]

Re: wet exhaust hose burnt through

Normal here does not exist, going to vary between engine and loading.
Why not do a flow test, take a decent pressured hose and see how they flow and if the water pressure is let out or retained by rust.

Ayuh,.... Agreed,... Exhaust hose gets burnt from a lack of water flow,...

Not the temps of the water....

When was the raw water impeller last changed,..??

 

[BoatingTimbo]

Re: wet exhaust hose burnt through

Not sure. Just bought the boat this spring. Should i consider replacing risers + elbows (or are the risers/elbows a combined part) on both engines for starters?

 

[Lyle29464]

Re: wet exhaust hose burnt through

closed cooling I would change the risers tomorrow. open system I would change it all.

 

[Bondo]

Re: wet exhaust hose burnt through

Not sure. Just bought the boat this spring. Should i consider replacing risers + elbows (or are the risers/elbows a combined part) on both engines for starters?

Ayuh,... Start at the water pump, 'n then Check for flows....

It wouldn't hurt to Check the manifold/ riser interface, 'n either change the gasket, or replace, if necessary...