Assuming your boat has 1.95 to 1 ratio you should be better off with F5 unless you load up with 8+ adults all the time… You will loose a bite at hole shot little but should pick up 2 to 3 mph on top end… F5 comes on standard for H240 with 5.7GXi DP but about 600 lb. lighter than SL242…. We have F5, F6 and F7 for our H260 (8.1GiDP) with 1.78 top 1 ratio and F6 seem to be the right choice… F7 picks up a few mph on top but loose grip at low speed especially for tubing or skiing…. But keeps lower RPM for cruising so not bad for a long distance trips… F5 for our boat is too much grip (or we should say unnecessary grip) at hole shot and will over lev a little at top end and also runs too high on typical cruising speed… We recently sold our F5 prop set since are not the ones for our boat… However, I feel F5 is overall right fit for SL242 with 5.7 GXi DP with light load.
_________________

08 H260 VP 8.1Gi DP.....Previous
2013 Crownline E6 Merc 8.2MAG BIIIX, DTS/SC