SXR TBM pump stuffer and 10/16 Hooker impeller, now cavitation off idle

[550/440]

I installed my 10/16 Hooker and a TBM stuffer on Sunday. Now I get intermittent cavitation from just off idle. I have a Q8 hull, andthe pump was siliconed in. I've checked the silicone and don't see any gaps or issues, just smooth silicone. Any ideas why I'm having cavitation issues? I replaced a small hub 9/17 that was in mint condition and didn't cavitate.

 

[Twinturbostang]

Did you forget the nose cone on the prop?

 

[550/440]

Nope, rubber nose cone installed. It's not a constant either, so it is baffling me.

 

[motoman96]

Why do you guys silicone your pumps? Never done it, never will, an never had an issue with cavitation. That's what the pump seal is for.

 

[550/440]

Pump seal won't fit on the hull. It's built slightly smaller. I suppose I could sand down the gel coat and open it up for the pump seal...

 

[tomski]

Pump seal won't fit on the hull. It's built slightly smaller. I suppose I could sand down the gel coat and open it up for the pump seal...

Be careful how much you grind where the pump seal is. There isn't much material there. Use Loctite 5900 flange sealant to seal the pump.

 

[OCD Solutions]

What kind of gap did you have between the impeller and pump vanes? was the new impeller setback at all?

 

[550/440]

It's a Hooker 10/16 - 5mm setback. I pulled the pump out tonight and redid it all. I'm headed to Grayland for some riding on Sunday, should be all set. Thanks for the advice/input.

 

[motoman96]

Pump seal won't fit on the hull. It's built slightly smaller. I suppose I could sand down the gel coat and open it up for the pump seal...

Grind the pump shoe to fit then....? Never understood the silicone in the pump, it's not a 440.lol

 

[550/440]

Fixed it. My seal job wasn't as great as I thought. I pulled it apart and found a toothpick sized leak. Sealed it up, let it sit overnight and headed out to the surf. Plenty of hook up and even felt good in the fluffy whitewash. Pulled my first backflip, some clean air and plenty of good stabs... I'm loving this new hull.

 

[Scorn800]

What size exit nozzle you running?

 

[550/440]

80mm. I need to go bigger, it has a lot of top end. I've still got to put on the X2 nozzle and tilt, it's 83^ mm.

 

[Scorn800]

82 or 83 should be real good. Do you know what your taching now?

 

[550/440]

Not yet, I just redid the pump w/ the new impeller and stuffer, and I can feel a bit more load on the engine. I need to borrow my bud's tinytach again and find out.