I have a 27 tall transom LT on a short transom 1648. What size prop do I need? Thanks.

Check with the engine maunfacturer.

Without serious mods - an 8" pitch is likely too much

Depending on boat weight and average loading a 5 - 6 - 7 is more likely

the manufacturer will be able to tell you the diameter and thread type...

the 9x6 is good on my 16 x 48 with a 23 vanguard-- but I want to try a 9x7 to see if there is anything left to get in speed before I cross the line of too much pitch for a full load...

Yall overthinking this prop thing as of late! The manufacturers suggestion is ussually spot on, with their prop. One from a different company will most likely perfom different, same one from same company might too! Just remember there is more to a prop than diameter and pitch. Go-Devil says 9x7 for a 27....they say 9x6 on my 25, yet It came with 9x7. Say a 9x8 wont work without mods? Been running the 9x8 with an extra blade half the year! I'll agree he'd have a hard time spinning a 9x8 2 blade with any cup. Ive only played with the cup on mine-huge difference in how they run. Gig, I think you'll have a hard time turning the 9x7...with heavy cup and any load. Load seems to make a big difference too. Just more to think about!

I have a 16HP motor that calls for a 9x3 prop, but I put a 9x5 Hill Marine prop on it and it runs a LOT faster. it doesnt dig in the really shallow stuff that great, but for the 100 yards of the really shallow stuff I run in, compared to the 3 miles of deeper stuff I run makes it worth it to me. When I replace my prop again, I think I'll go with a 9x4 and see how that one performs.

9X7 came stock on the 23 GDLT up until a year or so ago.