How do I know if I bent the prop shaft?

jeff7599

Cadet
Joined
Mar 25, 2003
Messages
19
Hello,<br /> I have a '96 Evinrude 88sp. I was going about 4000 rpm with a regualr prop and hit something submerged in a muddy area. My wife thinks she saw a plastic lawn chair. One blade got a good nick in it. I motored home at about 200 rpm not knowing I had bent the prop. So I really have two questions:<br /><br />How do I know if the prop shaft is also damaged?<br /><br />Did I cause any damage running the prop at 2000 rpm for 10 minutes. <br /><br />I didnt notice any vibrations. I only realized the damage when I got close to home. The engine itself was vibrating a little. Just coincidence. I just changed the lower unit lube today. Will that help identify any problems. I will be buying a new prop. Should I keep the old one?
 

dick

Chief Petty Officer
Joined
Oct 4, 2001
Messages
433
Re: How do I know if I bent the prop shaft?

Whats the compression? have you done a spark check?These engines only are running on the top two cylinders at idle to 1700 rpm so if you have a bad coil,bad cylinder or plugged lower carb(S) you won't know till higher rpm.
 

jeff7599

Cadet
Joined
Mar 25, 2003
Messages
19
Re: How do I know if I bent the prop shaft?

Before I went out today I changed the lower unit oil, new plugs, and checked the compression. Basically, I did a small tune up today before I went out and hit that chair. I live in south texas, so it wasnt a reef or big rock. Either a chair our a small rock.
 

ob

Admiral
Joined
Aug 16, 2002
Messages
6,992
Re: How do I know if I bent the prop shaft?

Jeff ,You could spin the prop and perform a close visual of the center hub or better yet,remove prop and do a runout with a dial indicator on smooth part of propshaft nearest the splines.Anything in excess of .002 mils needs straightening.
 

jeff7599

Cadet
Joined
Mar 25, 2003
Messages
19
Re: How do I know if I bent the prop shaft?

How exactly do I use that dial indicator. Do I mount it to part of the lower unit? Im trying to visualize how to fix that indicator to get a good measurement.
 

ob

Admiral
Joined
Aug 16, 2002
Messages
6,992
Re: How do I know if I bent the prop shaft?

Jeff , a good heavy piece of metal with mag base is sufficient for indicator.Just make sure it doesn't rock.Set on floor under propshaft and adjust as necessary.If you have an indicator clamp you can afix it to the anti-ventilation plate above propshaft.
 

jeff7599

Cadet
Joined
Mar 25, 2003
Messages
19
Re: How do I know if I bent the prop shaft?

OB,<br /> I noticed you are also in Corpus. I this a coincidence or did you find me somehow? I hit that chair over by Snoopys. If I understand correctly, Im going to remove the prop. And rotate the shaft with a piece a metal touching it to see if it gaps or moves. Noting if its bent.
 

ob

Admiral
Joined
Aug 16, 2002
Messages
6,992
Re: How do I know if I bent the prop shaft?

Just a coincidence that we are both from Corpus.What chair by Snoopy's.Was one floating in the water by the channel?<br /><br />Let me clarify runout procedure.First you will need a dial indicator with a pillow button attachment to perform runout.Either attach the indicator base to the anti-ventilation plate on the motor using an indicator clamp from a set,or magnetic base the indicator to a stable piece of metal on the floor under the propshaft to reach the indicator button to a smoothe surface of the propshaft nearest the splines.A 1/4 inch travel indicator is sufficient.Depress around half of its travel on shaft surface and tighten in place.Zero the indicator.Rotate shaft by hand slowly 360 degrees or 1 full turn noting the amount of variance from zero at any given point.insure that indicator returns to zero when one full turn is reached.Bare in mind that you will have some radial movement because of bearing clearance.Perform the 360 degree runout several times until you are satisfied that you have obtained an accurate reading.If you don't have access to an indicator you can secure the services of a dealer or machine shop cheap to perform this check for you.<br /><br />I've got one at the house if you want to borrow it or have me help you do a shaft runout.I'm right off of Rodd Field.Let me know and I'll give you my number.
 
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