For p=2 it is directly checked that there are no solutions. Assume that p>2. Observe that N=11p+17p≡4(mod8), so 8∤3pq−1+1>4. Consider an odd prime divisor r of 3pq−1+1. Obviously, r∈/{3,11,17}. There exist b such that 17b≡1(modr). Then r∣bpN≡ap+1(modr),
where a=11b. Thus r∣a2p−1, but r∤ap−1, which means that ordr(a)∣2p and ordr(a)∤p, i.e. ordr(a)∈{2,2p}.
Note that if ordr(a)=2, then r∣a2−1≡(112−172)b2(modr), which gives r=7 as the only possibility. On the other hand, ordr(a)=2p implies 2p∣r−1. Thus, all prime divisors of 3pq−1+1 other than 2 or 7 are congruent to 1 modulo 2p, i.e.
3pq−1+1=2α7βp1γ1p2γ2⋯pkγk,(∗)
where pi∈/{2,7} are prime divisors with pi≡1(mod2p).
2811p+17p=11p−1−11p−217+11p−3172−⋯+17p−1≡p4p−1(mod7),
so 11p+17p is not divisible by 72 and hence β≤1.
If q=2, then (∗) becomes 3p+1=2α7βp1γ1p2γ2⋯pkγk, but pi≥2p+1, which is only possible if γi=0 for all i, i.e. 3p+1=2α7β∈{2,4,14,28}, which gives us no solutions.
Thus q>2, which implies 4∣3pq−1+1, i.e. α=2. Now the right hand side of (∗) is congruent to 4 or 28 modulo p, which gives us p=3. Consequently 3q+1≡6244(mod3) which is only possible for q=3. The pair (p,q)=(3,3) is indeed a solution.