This is Raphael Pont's web site (he lives in Geneva, Switzerland).
The header design is interesting but I don't know if it gives any insights with respect to headers for the cars. My main concern would be that the boat headers are for a very narrow RPM range because boat propellers seem to deliver maximum efficiency at fixed RPM.
Still, looking at the engine setup gives some interesting insights and points to contemplate:
- The engine seems to be installed in reverse, i.e. the drive shaft exit (that would lead into the clutch bell housing) is near the bow (not near the driver).
- The angle of the engine is much steeper than it is in the cars (and going in the opposite direction), similiar to a car that going down a steep incline. This means that the oil sump construction must be different, as the oil pick-up tube needs to be longer because the oil pump location is (with respect to the oil level in the sump) higher than it would be in a car.
- The intake manifold and carb linkage is also completely different because of the reversed engine angle.
The attached image is from a confidential Frech dealer brochure with information about the performance of 2600 Sprint and 2600 SZ and its main competitors in the market place (Lancia, Mercedes, etc.). To bolster the sales argument for the cars and their engines, 1965 race results for boats were also included: