Prop Id help

[slim6969]

Hey there someone please help me understand what the numbers on the side of my prop mean. These are the only numbers I can find. I know the 17p is pitch what are the rest.

48-79572a4 17p

 

[slim6969]

Also is there numbers that will tell me the tooth count with out counting them all ??

 

[jimmbo]

Mercury part number
As for the gear ratio, what is the engine?

 

[slim6969]

It’s a 4.3 v6 Mercruiser with thunder bolt ignition and alpha one out drive

 

[slim6969]

The problem I’m haveing is that it seems the prop is sliping at high rpm and I feel like that’s what it’s doing because the rpms pick up but the boat almost feels like it slows down It for sure does not pick up speed. I’m going to mark the prop before I take it out next time and see if it does move off the mark. But honestly it might just be less time consuming to just buy a new one that why I’m trying to I’d the numbers on the prop

 

[jimmbo]

Sounds more like the prop is loosing its grip on the water. Does it occur when the engine is trimmed out a lot, on turns? I am going to assume it is an Aluminium Black Max prop. Not a high performance prop by any stretch of the imagination

 

[slim6969]

there is a very small window if I trim up where I gain a few rpm and I mean very small if I go past this very small window the boat loses speed Now I know that the prop is not out of the water as I’ve watched it It’s almost like if I trim up a bit it causes stress on the prop and makes it slip or that kinda what it feels like

 

[jimmbo]

When a prop loses it bite, slippage increases greatly. When you lower the drive does it regain its grip?

 

[slim6969]

Yes it does. Also if I’m running say 3/4 throttle and move the throttle to wot I can hear the rpms increase but the boat feels like it does not gain any of any thing it feels as it slows down.

 

[jimmbo]

What condition are the blades? Nicks? Filed areas? Chunks missing?

When you say you hear the RPMs increase, are you just hearing more induction noise, or does the Tachometer show a substantial rpm increase?

My guess is you are over trimming the drive too much for your current prop and you are experiencing ventilation/blowout. It might be due to a prop that has worn blades and/or damage tot he blades. Some higher performance props are designed to hold the boat higher out of the water at lower trim settings, and their blade shape/design can offer a more secure bite on the water.

 

[slim6969]

So I have a new tach to go in as the only one did not go past 2500 rpm and was lent a prop to try out so will post back on on how it goes next time I’m out with the boat