The 29-year-old former Great Britain international, who has scored 145 tries in 173 appearances for the Black and Whites, signed his new deal, which takes him to the end of 2015, before Sunday's pre-season friendly.
"I'm really happy to sign a new contract and it's great timing to come with my testimonial game but I'm not going to get sentimental, I'm only focused on making sure this is my best two years to come," Yeaman said.
"I was extremely frustrated with how last season went for me and I'm intent on making sure I bounce back this year and produce my best rugby. I love the club, I don't want to play anywhere else and I want to make sure that I'm back to my best week-in week-out."
Hull ran in five tries against the Tigers, with close-season signings Gareth Ellis, Daniel Holdsworth, Shannon McDonnell, Ben Galea, Joe Arundel and Jason Crookes all making their first appearances in the second half.
It came after an impressive showing from the club's young stars helped establish a 10-6 half-time lead courtesy of tries from Ben Crooks and Josh Bowden. And, with the club's senior players taking to the field in the second half, the Black and Whites added further tries through Aaron Heremaia, Joe Westerman and McDonnell.
Castleford's points came from an early try by former Hull KR centre Jake Webster, which was converted by Kirk Dixon.
Former London Broncos winger Omari Caro scored two tries on his first home appearance for Hull KR in their 32-10 win over Wigan at Craven Park.
The under-strength visitors led 10-0 after 15 minutes thanks to tries from Ryan Hampshire and Dominic Manfredi but Rovers responded with touchdowns from Lincoln Withers, Greg Eden and Micky Paea, all converted by Michael Dobson, to lead 18-10 at half-time. Liam Salter stretched Hull KR's lead with a fourth try and Caro struck twice to round off the victory.
Elsewhere, Australian prop Justin Poore was a tryscorer on his home debut as Wakefield gained a 38-10 victory over Featherstone and Elliott Whitehead scored four tries in Bradford's 48-6 win at Dewsbury.
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