Your a bit smaller than me Luke, so you should be able to reach it as I can, but it will be under the rear of the cockpit floor. I'm not sure of the relevance of that particularly though, as if the raw water pump is hot, there can't be any water going through it, so it stands to reason the pipe entering the exhaust elbow will also be hot. The problem must be the impellor or a blockage (or air lock) as no water is getting through the pump.
Ok, another silly thought. When the new impellor was installed, was it put in the right way, so the vanes are compressed in the right direction? The manual states the impellor should be installed with a clockwise rotating movement. This is to ensure the vanes are compressed i nthe right direction in the pumping part of the housing, otherwise when it turns, they will be pushing rather than pulling.