Quote:
Originally Posted by Rusty
Understandably Cats need to be hot to convert harmful pollutants into less harmful emissions.
I don't have a boat that is powered by a motor so I'm sort of in the dark about the engine safety features in newer boats. I would think that there would be some sort of warning light or sound that would tell the boat operator that the engine is reaching a dangerous and damaging temperature. To just see smoke coming from the engine compartment after it has already done some damage doesn't seem right.
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There's a temperature gauge and an audio alarm for overheating. If the engine is being pushed hard when the supply is interrupted, the rubber hoses in the wet exhaust system can get hot enough to melt and smoke (without actually failing) before the alarm goes off. That's what typically causes the smoke. The hose has to be marine-rated (typically SAE J2006 standard) which defines temperature resistance and flammability, among other things, so the chances of a fire from this situation are not as bad as you'd think.
Another cause of smoke might be the engine's serpentine belt heating up due to a stalled water pump pulley.
I'm surprised that the manifolds needed replacement from a single overheat situation. Non-catalyst manifolds usually survive that kind of abuse without issues and the innards of all catalytic converters can easily withstand absurdly high temperatures since they require them to operate. I wonder if they were swapped for purely cosmetic reasons. Malibu puts a lot of "bling" on their boats, so perhaps the engines are dressed up as well.