Motor judder in gear only

Hi. Can you help me out?
I have a Yamaha
~60hp 4 stroke high thrust motor.
~3½years old.
~13½x 15 - K prop., in excellent condition.
~1100 hours exactly...just changed the oils.
~Caribbean , tropical
waterside environment,
~average 6hrs per week, in three trips.
Maybe i noticed because of the added attention after the oil change, I'm not sure. (it has done this a little before) ...but from around 1700 to 2400 rpm, but ONLY in gear, the motor judders. (Forward and reverse. R, only tried it to 1700rpm)
Not a lot, but noticeably, compared to the same rpm in neutral.
The lower unit gear oil was plentiful and clear of milkiness yesterday when i changed it. Nothing on the lower plug's magnet. All foot/engine oil changes have been to the hour, from new.
I'm mystified.
Where i am is pretty remote and there is no worthy mechanic anywhere near....and I'm broke, right now!

Any ideas would be greatfully received. I'm very worried as we live alone looking after wild Amimals.. only indigenous indians close at hand, and the boat is our lifeline. 5 species of deadly viper present, so i try to keep the boat in tip top condition, as the anti venom is 1½hrs away and a Fer de Lance bite gives a window of 3 - 4 hours!!
Thanks a lot.

The cause of this judder while only occurring in gear points to a moving part, obviously. Have you pulled off the prop to inspect prop shaft and seal, free of fishing line or likewise debris? How about the condition of the prop, you say excellent condition. Be sure the leading edges of each of the blades are not compromised, as this will cause vibration. Next I would verify cylinders are within spec compression, along with verifying appropriate timing of each cylinder. Here is a link for a 2014 T60 (high thrust) to help with your troubleshooting:
https://www.vansoutboardparts.com/s...maha-shop-manuals/65-2014-yamaha-f60-jet/file

Also, I'd suggest visiting the forum website listed below, which is completely dedicated to yamaha outboards. Sign up and start a new thread, as you have on this forum. Be sure to list your engine's complete model number and year. This can be found on the engine bracket, I.D. plate.

http://www.yamahaoutboardparts.com