Slightly bend in Prop shaft?

[Ruggybuggy]

The 2004 50hp Merc 4 stroke that I've bought has a slight bend in the shaft after the seal. It's about .001 to .002 out (a guess, I haven't measured it yet). Is this going to be a problem? Previous owner said they never noticed any vibration. Local shop said they could straighten it for $300.

 

[Faztbullet]

Re: Slight bend in Prop shaft?

Re: Slight bend in Prop shaft?

If you can see the wobble by rotating /spinning prop with your eye its more than .001-.002 out. I have alo seen props with center mis-cast/machined that looked like shaft was bent, find another shop as for a additional $130 you can buy a new one. My machine shop charges $65 to straighten one. It takes about 10 minutes to remove it and is a very simple and straight foward procedure to remove and reinstall.

 

[Ruggybuggy]

Re: Slight bend in Prop shaft?

Re: Slight bend in Prop shaft?

If you can see the wobble by rotating /spinning prop with your eye its more than .001-.002 out. I have alo seen props with center mis-cast/machined that looked like shaft was bent, find another shop as for a additional $130 you can buy a new one. My machine shop charges $65 to straighten one. It takes about 10 minutes to remove it and is a very simple and straight foward procedure to remove and reinstall.

I'll measure and make sure it's out. I took the prop off and ran it at idle in gear and if you put the end of your finger on the shaft (threaded portion) you can see it's bent slightly. I was under the impression that a "special" tool is required to remove the shaft. I'll find a service manual.

Thanks

 

[sschefer]

Re: Slightly bend in Prop shaft?

You should double check the runout spec's for you engine. If you can find anything on a factory Merc engine that is within .001 I'd be shocked. Check your manual, but I think the prop shaft, drive shaft and crank shaft runout max is .006.

 

[Faztbullet]

Re: Slightly bend in Prop shaft?

I check my shafts in a lathe and have never seen a used stock shaft over .003 out and a new one is almost dead on.

 

[Ruggybuggy]

Re: Slightly bend in Prop shaft?

What would the spec be according to the manufacturer?

 

[Ruggybuggy]

Re: Slightly bend in Prop shaft?

So I got around to measuring the prop shaft runout. It's .020". So much for the old eye ball meathod. Would a bend of .010" still be a problem. A friend said if you can't feel a vibration don't worry about it and that he ran one similar to mine for years and never had a problem

 

[sschefer]

Re: Slightly bend in Prop shaft?

So I got around to measuring the prop shaft runout. It's .020". So much for the old eye ball meathod. Would a bend of .010" still be a problem. A friend said if you can't feel a vibration don't worry about it and that he ran one similar to mine for years and never had a problem

In my mind, .020 is quite a bit but not knowing the spec's I can't say if that is o.k. or not. Perhaps someone that rebuilds L/U's can chime in and give you advice.

 

[Faztbullet]

Re: Slightly bend in Prop shaft?

Take it to a GOOD machine shop and have straightened, if they are good they will know how to use press an v blocks. If they can get it .006 or under it will be fine. If you run it like it is it will eventually cause seals to wear and fail and rear bearing in carrier may fail due to increased side loading. If its bent it vibrating even if you dont feel it.

 

[sschefer]

Re: Slightly bend in Prop shaft?

Faztbullet has given you good advice. Get a quote for straightening it and replacing the seals. You may find that there's already significant damage. If that's the case shop eBay and Craigslist for a replacement lower unit. It might be cheaper in the long run.

I would not run it. If it were to fail and lock up you could end up damaging the splines in the crankshaft. Not something you want to do.