Sarisbury were in a spot of bother when Colin Day departed to leave the score 42-3 in reply to the visitors’ 260-4.
But Michael Bond came out to help Mottola add 172 for the fourth wicket.
Bond was eventually out for 69 - his second highest league score, behind his 123 for Sarisbury 2nds against Otterbourne a decade ago.
Mottola, though, powered on before he was sixth out with the score on 218 - just two short of his hundred.
Sarisbury still had work to do but Matt Reeves (16 not out) and Jon Floyd (12 not out) saw them home with a 26-run unbroken stand for the ninth wicket.
Old Netley openers Ben Charrett (75) and Adam Comber (61) had earlier put on 146 before Himat Singh (61 not out) joined in the fun.
Ahmad Khan bagged six wickets as United Services Portsmouth claimed their first league win at the fifth attempt.
The opening bowler was on fire with all the wickets as Paultons slumped to 40-5.
Hugo Hamiid (60) and Simon George (31) put on 83 for the sixth wicket as the visitors posted 172 at HMS Temeraire - Khan finishing with figures of 8-2-32-6.
Ian Cole (51) and Raj Das (45) laid solid foundations when US replied with an opening stand of 104.
Vineet Vajpayee (27) helped the run chase and the hosts eased home by six wickets with more than four overs in hand.