Not familiar with this issue, but could you use safety wire to keep the bolts in?

zt260 how does the 5 blade max handle DOES IT GIVE ANY BOW LIFT.?

It's not bad in stock form with the shorty. I had BBlades lab it for more bow lift and I have picked up 7mph in total over the Bravo. I would say the bow lift is similar to a stock Bravo prop after the labbing.

My v bottom would not plane with out the plate. It didn't make much of a difference with my cat though. I know that my plate cleared everthing that I ever mounted on it, including the the big Hydromotive Q4 by around 1/4". My plate was stainless and it had 4 button head bolts that were through bolted through the cavitation plate. Naturally, lock nuts were used. The nice thing about having bolt through the cav plate is that even if one were to fall out, chances are very small that there would be any damage to the prop.

ZT260 THANKS you have a checkmate? what speeds and rpm are you getting, pitch size .I will use brett too going back out sat to test more getting readings between 80 to 83 gps 5600 to 5800rpms 26 b1 labbed it might be a 27 not sure so going out one more time.

Cord, You are talking about a differnt plate than Quent is..

On the Imco shortie the cavitation plate is mounted on top of the upper housing cav plate. There is also a plate that covers a hole left by the short length of the imco lower on the bottom side of the upper housing.. that is the plate he is referring to with a countersunk flat head machine screw holding it in.

If it were me, I would fill that cavity with something.. Silicone or bondo or something like that.. For a test you could try some kids clay, maybe. I dont think it will have much effect, but water likes to slide off things rather than get hung up on open cavities..

Hope this helps.
Dick