Mortar differs from concrete in a number of ways, crucially from a transport perspective it is weighs less.
The reduction in density makes it possible to carry more material within any given payload weight, but only if the drum is big enough! Another characteristic of mortar is that it will flow relatively easily, and accordingly a drum mixer for mortar does not need the focus on discharge rate given to a drum for concrete. In fact since the job site will typically utilise tubs for the Mortar, a slower more controllable rate of discharge would be an advantage.
For mortar applications, Hymix offers the SS range featuring larger drums, a slower discharge rate and mounted further forward to keep the axle loadings right.
The SS model shown below features a Hymix Colour Master. The Colour Master unit will allow pigments to be blended in to smaller batches of natural mortar discharged from the main drum. This saves transport costs and reduces the waste from washing out the liner coat on the larger drum. This system is ideal for a large number of small volume drops of different colours. For larger drops with fewer colours involved you may wist to consider a Hymix MDV specialist Mortar Delivery Vehicle.