Custom/Hybrid Driveline/ pump issue?

[g-ski]

Looking for some input or ideas on something my ski just did.
Background--Rickter FS1 hull, ltd 701, stock pump, Skat freeride prop (12/17?)
I was out riding and my Worx intake broke (it was old, had a crack in it, already had new one ordered). Part of the grate broke the OEM plastic pump shoe so I ordered a replacement from Blowsion (had to tap my own installation holes; yea I called and whined). Put everything back together. Boat ran good on trailer. Went out yesterday and ski would only run at about 1/2 effort similar to maybe bad cavitation. Rode in, took it out of the water, same thing, revs normal, back into water;same problem. Then as I was riding at full throttle I felt a "thump" from I'm guessing the pump/drive shaft area and the boat stopped. Now kneeling, I noticed the boat seemed to be going backwards. About 10-15 seconds of this another thump and the boat revved up and took off. I then rode for about 5-8 minutes and everything was normal. I was out of time (pick-up kids) but now feel like everything is good. Any ideas?:question:

 

[McDog]

You can get cavitation if the pump shoe isn't sealed all around. No idea on the thumping and running backwards part.

 

[g-ski]

When I first put this ski together I did not seal pump area sufficiently so I know first hand how important that is and how even the slightest gap makes a big impact. I feel like I sealed everything very well this time. If that was the issue it would not have ran great at the very end. The thumping and the backwards is what really has me curious. I can't wait to get back in the water and verify that everything is now good. The new shoe and the grate seem to make a difference.

 

[Billybo455]

weren't the epic guys having their boats reverse when jumping with low idles?

 

[Matt_E]

Used to happen quite a bit on older analog MSD TL systems.