The 2910 is rated at 30 HP not 29. I guess because of the name, it keeps getting called 29 HP. Even the Carver web site incorrectly lists it at 29 HP even though the Kubota specs say 30. I realize it is only 1 HP but if someone said the 2710 was rated 26 HP or the 2410 was rated 23 HP, I am sure they would get corrected.
The difference in the engines between the B2710 and the B2910 is more than an increase in fuel flow. The engines have different displacement. If you compare bore and stroke you will notice that the B2710 engine is a 4 cylinder version of the 3 cylinder engine in the B7500/B2100, and the B2910 engine is a 4 cylinder version of the 3 cylinder engine in the B2410/B2400.
Andy