Diesel exhaust - heater

It is entirely possible that there is nothing wrong and the cause could be the way the boat is positioned to the prevailing wind. If the exhaust outlet is up wind of the air vent inlet for the compartment where the heater is exhaust gases can sometimes get drawn back into the boat. This is especially true at heater start up where the fan speed is low to promote initial combustion, and consequently at startup exhaust velocity is also very low so doesn’t clear the hull so well.

Having said all that you do need to find out what is happening. Having experienced similar which turned out to be caused by the wind direction and slow fan speed at startup. To give myself a bit of reassurance, I installed a carbon monoxide detector, the view being that with the heater, the engine and a gas cooker onboard there were too many opportunities for a mishap in what after all is a small volume container.

Hope this is useful 

Simon 

I took it out off the boat and found out the exhaust was completely gone.

It wass helt together by its isolation around it.

Sins then I check it every year…..