First grade battled to reasonable scores but were unable to defend them on both days, while third grade took the honours against both Joondalup and Fremantle.
Brayden Sutton and Craig Simmons batted well to give the Mariners something to bowl to after being put in on a typically spicy Iluka wicket against Joondalup on Saturday.
As the wicket became easier to bat on, the total of 7-164 did not seem daunting.
Joondalup got the runs with five wickets in hand and 10 overs to spare to showcase their credentials as reigning champions.
Aidan Andrews, bowling with his usual economy and craftiness, kept the Mariners in the match with 1-18 off his allowed 10 overs and was at it again on Sunday against Fremantle.
In his third season in the top grade, the paceman was again the team’s best bowler with 2-32 in Fremantle’s 7-212 at Lark Hill.
Rockingham-Mandurah, in a strong position in all of the washed out matches last week, could not find the upper gears as batsmen made starts but were unable to go on.
Tony Coulson topped the batting with 31 as five of the top six made double figures in the Mariners’ 9-151.
Third grade swamped Fremantle on Sunday at Lark Hill, keeping the visitors to a measly 8-137 in 45 overs.
The batsmen were then able to cruise to 3-139 with more than 15 overs in hand.
The day before, Tom Lewis and Syd Menezes sensibly picked apart Joondalup’s bowling to guide the Mariners to 167.
The Mariners have a perfect record in third grade, as the bowlers played their roles to a tee, rolling the Centurions for 129.
The results were not so good in the other grades, as the seconds conceded 5-236 against Joondalup and could only muster 8-195 despite John Murphy’s 66.
Against Fremantle, the Mariners amassed 7-220 but were swallowed by the home team, who knocked over the target with only three wickets down.
Fourth grade lost both matches, as did the women’s entry into the expanded WACA B grade competition against newcomers Joondalup.
Rockingham-Mandurah scored 3-86 in the T20 game before the Centurions gathered the win with four overs left.
The under 15s look like contenders again this season with a second consecutive win.
The Mariners squeezed Joondalup to just 8-124, with Zachary Moody snaring 3-17.
Joel Humble got the team home with a fine 93, featuring eight fours and two sixes.
Levi Muller made 72 but the under 17s fell eight runs short of Joondalup at Iluka in a very early start for the trekking Mariners.
Next week the seniors play Gosnells in the third of four one-dayers.
The female team plays Subiaco Marist away, while the juniors begin a two-day fixture against Bayswater-Morley.