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Thru hub exhaust

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rob_boyd

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will someone exsplain the diff

will someone exsplain the difference of thru hub and thru and over exhaust my boat is a 1989 ranger354v with a 150 faststrike 1991the prop that came on it is a 13 1/2x23 4 blade it has a vibration and iam going to replace it i was told that i needed a 14 1/2 x 23i tested a 3 blade 14 1/2x23 and eliminated the fibration thanks for help
 
"thru hub,...exhaust goes thru

"thru hub,...exhaust goes thru prop hub,as yours does.....the other,i think,u r referring to,would create massive cavitation,...for very high speed application and light weight,....its a prop,that the hub is just over the splines,exhaust goes belching out of lower unit,all around it.
u want to stay w/a thru hub,w/whatever prop u decide."
 
"Some hi-perf props have holes

"Some hi-perf props have holes in the hub in front of the blades just behind the gearcase. These are typically large, high pitch props for high speed operation.

If operated as a normal thru hub, they would lug the engine down and kill the hole shot. The holes add a little exhaust to the water in front of the prop at low speed. This allows the powerhead to spin up into it's powerband. As the prop spins up and the boat starts to plane out, the exhaust from the holes stops. The prop then attains full grip. As the speed continues to pick up, a "wall" of water flowing along the holes helps fully block them, and the forward motion of the boat sucks the exhaust out the back of the open hub. The prop then operates at minimum slip.

As for the vibration you experienced, the prop may have been out of balance or have a partially failed rubber insert in the hub."
 
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