I can not give you an authoritative insight into Amel's reasons for reducing the size of the hose, but...
The total volume of the exhaust hose is a design criteria for the water lock. The box needs to be able to catch and hold at least one hose full of water without overflowing back to the engine. If the hose run is long, then they might have needed to neck it down a bit to keep the volumes matched.
If the horsepower of your new genset is equal or less than the original installation, then I would match the exhaust system as originally designed. If your new genset engine has higher horsepower rating than the original, I'd have an expert on engine installations look it over to be sure the exhaust system is sufficient.
Annapolis, MD, USA
---In amelyachtowners@..., <mfw642000@...> wrote :
Hi, I am installing a new genset into a super maramu 2000.
The engine is a kubota with a 50mm hose going to the vetas water lock. On the outlet of the water lock the hose reduces to 40mm. This is how the original is installed. It has a reducer 50 to 40mm glued into the water lock.
Can anyone help with the reasons why the hose is reduced in diameter?
The generator supplier advised to have a 50mm hose going on the water lock outlet.