Hurth ZFm-10 Slipping after 250 hrs

[bendoo]

replaced it 250 hours ago after the last one (a smaller hurth zfm-5) tanked.
yes I have a folding prop and no doubt that is not helping.
I will replace the fluid (fluid looks ok, but just a touch brownish grey) and the linkage is working correctly. haven't checked the damping plate, but it is the rubberized type and I would be surprised if that were the issue as I replaced it as well 250 hrs ago.
questions: 1) any other diagnostic I am not thinking of 2) can a transmission be bench tested? 3) any thoughts on changing out the prop at anchor (we are in Panama w/ limited access to yards etc) .

thanks in advance for any help.

[bendoo]

question 4) is there a "clutch" adjustment I can make....not seeing any reference to that in the owner manual.

[Dynamo1181]

Two points: I had what I thought was a slipping issue but after buying a new Hurth, I found that my Max prop was not fulling deploying, giving the appearence of slippage. I use a combo of ATF type Mercon and Type F. A rebuilder told me that the type F fluid has more bite that the straight Mercon fluid.
I had a friend who thought he could use 30W motor oil. After several hrs running he had a severe clippage issue.
My Hurth was an HBW250.
Be certain you dont have a prop issue!!!
A