[Sans Peur]

I had a 40' sport fisher (not a Tiara) that would surge water on the port side. Starboard would run nice and even but the port would push a bunch of water every 5 seconds. After digging around in the engine room I noticed the engine exhaust was exiting on the starboard side of each engine so the stbd engine ran straight from the engine out to the back if the boat. The port engine exhaust came off and made a 90 degree turn across the rear of the engine then made another 90 degree turn towards the rear of the boat. This allowed water to build up in the exhaust tube and once it got to a certain point the exhaust would overtake it and push it all out creating the surge.
I lifted the exhaust to make a cleaner angle and the surge disappeared.