I need to add vented loops to the coolingwater intakes on my yanmar3GM30 . I am in Canada and the boat is in Grenada . Does anyone know the id. of the intake hose . The water pump is the stock one.
According to the manual (which I have here) the ID is 13mm, but I haven't field verified on the engine.
[Edit] And then I look at my service manual (as opposed to operation/installation) and the piping diagram shows 20 on the 3GM30 and 24 on the 3GM30F. Won't be near the boat today, so hopefully someone else here can verify [/edit]
When you install a vented loop in the engine seawater circuit, you have to install the vented loop on the pressure side of the seawater system, downstream of the sea water pump. If you install the loop on the suction side of the system, before the pump, you will suck air into the system when running the engine, possibly causing overheat problems or damaging the pump impeller.
There I was, just thinking of the question as asked, and not the implications.
Not even much point to a loop on the pressure side, if the pump impeller is sound then a break in the discharge line won't result in flow anyway (because the rubber impeller has to be spinning in order for there to be flow through the pump). So would take a failure of the impeller (blade loss) and failure of the hose before your vented loop saves things. Depends on how much belt-and-suspenders you like.