Engine water in sizing

[vic008]

Vetus specify 20mm water in for the engine heat exchanger. Just bought skin fitting, ball valve, and notice down to 12.4mm bore for some of this stuff. Should I ensure all fittings have 20mm bore? Thank you

 

[ChromeDome]

Given that "Vetus specify 20mm" there is no reason to go with half of that?

I'd go a far way to prevent overheating and all the mess & problems that could cause.

 

[scottie]

Apart from future proofing the. Engine water requirement must determine pipe sizes

 

[lustyd]

The pump will have a metal bore, measure that. The strainer will have hard plastic bores, measure those. I seem to recall mine were 3/4" fittings for my MD2040 which loosely aligns to 20mm I think

 

[vic008]

The worst culprit is the nipple at the inboard end, barb to take 20mm hose so it's bore is going to be considerable smaller.

 

[ChromeDome]

As suggested the size of the hose fitting on the pump (suction side) should guide you.

Depending on the fitting's design you may need a bigger to provide the inner diameter, still to fit the 3/4" (19.8mm) hose to the pump.

 

[scottie]

Worth remembering that boat builders may use water setups to suit various options to reduce inventory and fit largest size as it will suit all

 

[Freebee]

I would go for the biggest reasonable size you can better too big than too small if vetus specify 20 mm why would you go an smaller???

 

[ChromeDome]

If we can get the engine/pump ID it's easy to get the pump manufacturer's (most commonly Johnson/Jabsco) data sheet.

Apart from what's stated by Vetus restriction is systems may play a role also

 

[B27]

I'd be concerened that a small skin fitting will be easier to block with weed or debris.

The flow rate is probably not huge, it will be in the data somewhere. You could work out the pressure drop of bends and small fittings.
If your system is short and direct, a small fitting here and there might be fine.

You might find Vetus spec the same fittings for much bigger motors?

 

[Tranona]

The Vetus 20mm is misleading - that is the bore of the hose. You need a 3/4" BSP skin fitting and valve with a tail to take 19mm hose. Either DZR brass, bronze, or more likely TruDesign composite where you are. all standard stuff. The intake spigot to the water pump takes 19mm hose which is the giveaway as are the spigots on the water strainer. Almost all small heat exchanger engines use this size. Older seawater cooled engines like Bukh and Yanmar GMs use 1/2" and bigger (60hp+) use 1".

 

[saxonpirate]

The Vetus 20mm is misleading - that is the bore of the hose. You need a 3/4" BSP skin fitting and valve with a tail to take 19mm hose. Either DZR brass, bronze, or more likely TruDesign composite where you are. all standard stuff. The intake spigot to the water pump takes 19mm hose which is the giveaway as are the spigots on the water strainer. Almost all small heat exchanger engines use this size. Older seawater cooled engines like Bukh and Yanmar GMs use 1/2" and bigger (60hp+) use 1".

This.. ^^^^ 3/4" BSP skin fitting and 19mm tail on the hose..

I sorted my Vetus MD4.14 several years back with the above sizes.. no problems whatsoever..