do I need a new prop?

Reply

  #1  
Old 04-12-03, 04:19 AM
Member
Thread Starter
Join Date: Sep 2000
Location: Lapeer, Mi.
Posts: 52
do I need a new prop?

My 40 hp Mercury, about 10 years old, will sometime go to real high rpm as if the prop quit turning. If I keep a low power setting of around 1500 rpm it seems to work ok.
Is a prop make in such a way as it will spin on the bushing that fits onto the spline of the out put shaft?
High rpm's and what seems like cavitation is my problem I need help with.
 
Sponsored Links
  #2  
Old 04-12-03, 04:48 AM
fewalt's Avatar
Member
Join Date: Feb 2001
Location: sw VA
Posts: 3,100
donnyjay,

I doubt you need a new prop. I can't remember for sure on my Dad's old Merc40, but you just may need a new clutch.

The BoatCop will be here shortly for the final word.

fred
 
  #3  
Old 04-19-03, 08:22 PM
BoatCop
Visiting Guest
Posts: n/a
Most props are made with a neopreme (rubber) bushing between the hub and the prop itself. After years of exposure to water, heat and exhaust gasses the neopreme breaks down, and the spline will spin, just as you describe.

The neopreme "bushing" is only a few milimeters thick, and is designed to reduce harmonic vibration in that prop, and also act as "weak link" in case of the prop striking something it shouldn't (like a rock). The neopreme will absorb the majority of the impact shock, and reduce it before it's transmitted to the drive gears. Often that's what destroys the bushing.

There are 2 remedies.

1. Buy a new prop
2. Have yours re-conditioned

If it's an "old" 40, reconditioning may be the best bet. It isn't that expensive, and they can also fix any dings or flaws in the blades, and even true up the pitch.

I'm not sure what they get for prop jobs in your neck of the woods, but I pay about 75 bucks when I need mine done. I use high performance stainless props, 21 X 19. The one for your 40 is probably aluminum and much smaller, so it shouldnt be that expensive.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes