Let’s start with a point of clarification. The D13 is offered in two configurations. The inboard “version”, if you will, is the labeled the D-13 1000. It is also offered as the D13-IPS 1350. The difference in nomenclature comes from the fact that, when coupled to a Volvo Penta’s IPS drive, the boat into which the IPS system is installed will experience the performance equivalent of a 1,350 hp diesel inboard. Basically, since IPS features lower drag, having no shaft and struts, and forward-facing, dual-prop propsets for loads of blade area in a smaller diameter, it can deliver higher performance than the inboard equivalent. Boating’s tests over the years corroborate this relationship.