Tank should come with female threaded fittings installed
So you won't need a hole saw...all you'll need to buy are the male thread-barb plastic --PVC or Marelon--hose fittings...and yes, both straight and 90s are available from just every marine store. No, there is no such thing as "marine grade" plastic plumbing fittings...though some sold at hardware stores have walls that are too thin to be suitable for use on a boat.
Inlet and outlet should be 1.5". Avoid gray PVC 1.5" because nominal 1.5 x 1.5 is actually 1.5 OD at the threaded end, but 1.5 ID at the barbed end...making 'em 1 5/8 barbed, impossible to get a hose onto. Gray PVC is ok for all other sizes, though.
Hopefully you specified a 1" vent fitting...if not, you'll need a 5/8" thread-barb tank fitting.
Do NOT use ANY sealant on the threaded end, only Teflon tape...nor any sealant whatever on the barb end. Warm the hose a little--do not overheat!--and use a little dishwashing liquid or K-Y as a lubricant...double clamp all connections, with screws 180 degrees apart...or at least 90 degrees if access makes 180 impossible.
Never heat a hose to make it bend tighter than it wants to bend willingly...break it and insert an inline radius fitting. And use 45s or 90s at the tank or thru-hull if the hose has be at an angle...don't just pull it, 'cuz that'll cause a fitting to leak.
And finally, don't overtighten the fittings in the tank. Tank fittings are NPT standard, which is slightly tapered (too slightly to see in a fitting that short)...over-tightening will crack the female collar, if not immediately, in time. Just one turn past hand tight, plus enough to aim an elbow where it needs to go is as tight as they should ever be.
