X-Shark

Here's how to check for a Spun hub.



Use a bright colored Sharpie Marker.



Make a mark on the edge of the prop and hub. This will be what is called a "Witness Mark" Those marks will be aligned with one another.



Go run the boat and hammer the throttle. You don't have to take it far from the dock to do this.



Bring the boat back to where you can get a clear view of these marks. If they are misaligned your hub is spinning and needs to be replaced.

SCUBA Junkie

Same thing happens on my boat. 150 Zuk 2 stroke pushing 20' deep V. Sometimes when Igo from very slow to firewall, acts like it grabs then rpms shoot up. Come back just a little on gas, everything comes together and we get up and go. Hub is not spun, motor is mounted with cavitation plate approx 1-2" below keel. It sounds and feels like cavitation, but I don't think the prop is pitched wrong as the rpms at full throttle are right on the money.

Breeze Fabricators

Alright guys this one I know. I was a quicksilver propeller franchised and "factory trained" (I went to a Merc sponsored school for about three consecutive years) for 15 years. His problem is almost surly cavitation. The spun hub problem is almost always as you are coming out of the hole and the boat il absolutely NOT plane off. He needs to check to see if a bolt head on the lower unit is sticking out further than it should. This causes a low pressure are to form behind it. Water boil in this area and allows thevapor to stream back and grow large enough to cause the prop to quit pushing water . A large bubble will form until he comes off a plane and slows down until clean water gets to the prop. He should check his trim angle as he could be pulling air around his anti cavitation plate which would do the same, The otherplace gas could be leaking into the water stream causing the problem would be if he put his thrust washer which goes in front of the prop. This will allow exhaust gas to leak out and fowl the blades until enough forward speed is achieved to collapse the gas bubble onto the hub and allow the blades to bite.

Now as far as a prop breaking loose while under way. That is usually caused by grass wrapping around the front of your lower unit and again causing the low pressure steam thing to happen. If it is happening while in a tight turn then you can have more cup added to your prop and that will end most cavitation problems caused by trim hight or breaking loose in the turn. You also need to check and be sure your transducer or livewell pick up is not too close to the propeller. This will also cause watervapor to stream down and cause your prop to cavitate. I can fix your problem as I still have the tools for cupping props and used to do alot of custom race work on propellers. I don't mind helping you guys out. :mmmbeer

__________________
Tim Scallan
Breeze Fabricators Inc.
4220 Gulf Breeze Parkway
Highway 98
Gulf Breeze Fl.
32563
850 554 6172/934 8609
BreezeFabricators.com

Bigg J

thats some hard core info. preciate guys.

If it helps my motors are volvo pentas 130 i/o. Prop size is 14.25x23R S and 14.25x23L S

I have no idea what that means.

sosmarine

That shines a different light. I think we were assuming, I know bad thing, that you had removed your lower unit to change your impellers. But that obviously is not the case. And did the RPM on both engines increase?

Bigg J

:banghead man I don't know, I forgot to look at the tachometer when in did it. My instinct was to turn around and look back to see if anything is obvious to why its reving up. It sounded like it was just one motor.

The props do have a couple of minor dings and I did get into some shallow water while running.