Prop Cavitating (catching air?)

[SW_Boater]

Problem solved. Discovered the 12vdc Boatstogo air pump wasn't putting out the correct air pressure. Although it's supposed to be capable of producing up to 12 psi (80 kpa) via an adjustable knob, it was only putting out a fraction of that even when adjusted for max output. Received the K-Pump air pressure gauge today and pumped up the boat using a manual K-Pump to the recommended pressures. Also installed a hydrofoil. Boat now gets up on a plane with no problem with zero cavitation/ventilation issues.

 

[Texasmark]

Try this : Trim OB to sit on transom perpendicular, that's at 90 deg, usually move trim pin to second/third hole out transom. With wife sitting up front and you sitting rear go for full throttle on flat, calm no wind water cond to plane out the Sib. Once on plane pull head out middle transom and check at which lower leg is wayer flow passing at speed. Can sit at rear tube or on deck next to transom.

Check if passing between middle or lower Cav Plate, report your findings, will go from there. Don't forget to fully inflate your Sib to al least 3.0 PSI on all air chambers including keel.

Happy Boating

When I read his post I thought immediately of you. If I hadn't seen your response I would have responded by telling him to ping you. If anybody should be able to answer his questions you should/would.

Happy Boating!!!!!!! Grin

 

[Sea Rider]

Thanks Texasmark LOL!!

SWB, are you plainly satisfied with the better water combo performance or want to go to the next level...

If so :
-Change 8 HP car for a 9.8 carb
-Buy an induction hour/tach Tiny Tach or Hardline one
-Go for one less pitch size
Will have a 9.8 HP-OB running at near max wot range, superb hole shot and more top end speed with 2 up than before.

Would recommend to trim OB for Doel Fin to ride parallel to water surface once combo is on plane, if not, fin will achieve extra water drag which will slow combo down a bit. inflate the air deck to full 12 PSI if been inflating it bit less, standard air floors don't hold their pressures for long time periods, are prone to deflate during boat use, must be re inflated from time to time. Used to inflate my old air deck Sib to 14 psi using a tire electric inflator hooked to a hose with attached air valve. Worked much better.

Happy Boating

 

[SW_Boater]

Thanks Texasmark LOL!!

SWB, are you plainly satisfied with the better water combo performance or want to go to the next level...

If so :
-Change 8 HP car for a 9.8 carb
-Buy an induction hour/tach Tiny Tach or Hardline one
-Go for one less pitch size
Will have a 9.8 HP-OB running at near max wot range, superb hole shot and more top end speed with 2 up than before.

Would recommend to trim OB for Doel Fin to ride parallel to water surface once combo is on plane, if not, fin will achieve extra water drag which will slow combo down a bit. inflate the air deck to full 12 PSI if been inflating it bit less, standard air floors don't hold their pressures for long time periods, are prone to deflate during boat use, must be re inflated from time to time. Used to inflate my old air deck Sib to 14 psi using a tire electric inflator hooked to a hose with attached air valve. Worked much better.

Happy Boating

Will definitely keep these mods in mind, Sea Rider, thanks. Right now, just savoring the fact we resolved this whole cavitation issue. We originally we had plans to use the boat to sightsee the Black Canyon area on the Colorado River the last few days. Unfortunately, we spent all this time troubleshooting the boat. Today we've got to hit the road. Learned a lot these last few days. We should be good to go next time