Fuel Pump Orientation

All we can do is provide the information stated by Rotax and information based on our experience/testing. It's your engine and entirely up to you regarding what you do with it and what advice/instructions you wish to follow. 

This article provides information regarding fuel vapor lock. https://www.rotax-owner.com/en/flightsafety/476-ai476

As stated on page 103 of the Rotax 912 installation manual: The design of the fuel system is the responsibility of the aircraft manufacturer. The fuel system must be designed to ensure that the engine is supplied with sufficient fuel at the correct pressure in every operational situation. Operating limits must be adhered to. https://www.rotax-owner.com/pdf/IM_912_Series_Ed3_R0.pdf

Repositioning (re-clocking) the fuel pump inlet and outlet ports are not permitted by Rotax and will void the warranty of the engine or component. (Rotax did state it voids ALL warranty)

Some people will either use 100LL or a blend of 100LL when they are having issues with the vapor lock or operating in a very hot climate. TCP or Declan cuts down on the lead build-up when using 100LL. With that said, the entire fuel system design needs to be optimal and should be thoroughly tested in multiple weather and flight conditions to ensure there are no issues. 

Rotax -Owner - If you read my initial question it was a "random thought", speculative if you will. 

My last Rotax powered aircraft did show fuel vaporisation symptoms, on a number of occasions, when ambient temperatures were in the high 30C's.

I was/am well aware of the potential for Rotax 9 carburetted engines to exhibit this characteristic and manage accordingly (without the need to resort to leaded fuel) - its no more of a "problem" than managing density altitude changes - just part of good piloting.

Mitigating adjustments (return fuel line/insulation/improved cowling air flow) that can be made, should be available to the pilot.This should include fuel delivery hose routing options, as long as it does not negatively impact on safety, which in my mind includes engine operational reliability and service longevity.

My enquiry, though speculative is genuine, so I find the responses from Rotax, as conveyed by you, to be disappointingly unconvincing eg if there is no change to the supply/delivery level of a fluid the "head" remains the same no matter the length of pipe or its routing.

Looked at my engine set up this morning - I now think that  90 degrees down (vertical), would be optimum (assuming pump casing can be re oriented)

What about the drain?

Roger Lee wrote:

What about the drain?

Drain stays as is Roger - my speculation (for that is all it is) is that the outer cap, with spigots, can be rotated, with the base remaining as is. 

If someone, out there has an old pump, they could remove the screws, examine the interior, to asses ability to rotate cap/spigots,  and give me a definitive answer to my question.  Otherwise I will do this myself  - in 5 years (:.