Bent prop shaft? ruined prop.

[dieselram94]

It was a good day on the lake until my wife said let me drive. Well I think she hit a rock. she was going about 10 mph or so when she hit. Spun the hub in the prop. Flo-Torque II or something like that. The oil may have about 5 hours on it and had some shavings on the magnetic plug. We ran it for about twenty minutes or so trying to limp in. The skeg has a SLIGHT bend to it , and the aluminum prop is destroyed (tips mangled). As close as I can measure the propeller shaft run out is about .2 mm. maybe less ( can't hold dial indicator very steady). do you guys think there is any major damage? I think the hub in the prop did it's job.

 

[HHIBouy]

Re: Bent prop shaft? ruined prop.

It was a good day on the lake until my wife said let me drive. Well I think she hit a rock. she was going about 10 mph or so when she hit. Spun the hub in the prop. Flo-Torque II or something like that. The oil may have about 5 hours on it and had some shavings on the magnetic plug. We ran it for about twenty minutes or so trying to limp in. The skeg has a SLIGHT bend to it , and the aluminum prop is destroyed (tips mangled). As close as I can measure the propeller shaft run out is about .2 mm. maybe less ( can't hold dial indicator very steady). do you guys think there is any major damage? I think the hub in the prop did it's job.

I doubt that you did any damage other than what you can see. I hit the boat ramp when loading as the wind gaught the bimmi and swung the back around. I bent the last 2 or 3 inchs of a SS prop, and every thing else was fine.

 

[sethjon]

Re: Bent prop shaft? ruined prop.

If you were going that slo you probably got lucky especially since you had an aluminum prop. You'll know for sure when you put on a new prop and try it out.

 

[Alpheus]

Re: Bent prop shaft? ruined prop.

As close as I can measure the propeller shaft run out is about .2 mm. maybe less ( can't hold dial indicator very steady).

You cant hold a dial indicator and get an accurate measurement. It must be mounted on a firm base...

 

[dieselram94]

Re: Bent prop shaft? ruined prop.

I slipped on a old propeller and spun it and it looked as if the hub of the propeller was wobbeling a very slight amount. I didn't tighten it down as I didn't have the correct hardware for that prop on hand. If it really is bent some I wonder how long it will live like that. The local shop wants about $800 to change the shaft so I would be better off going with sei and replace the entire drive and get the fault free warrantee. I have a new prop coming and will see better if it really is bent. I probably will just run it and see how long it lasts. I also wonder if it was already bent some as previous owner took a SMALL chunk out of the skeg and it had a michigan wheel prop on it when I got it.
Any one else running a bent shaft?

 

[a70eliminator]

Re: Bent prop shaft? ruined prop.

Yep, my OMC Cobra is .012 out, thats over double the max, remarkably hasn't leaked at all, no noticable vibration either.

 

[bryank75]

Re: Bent prop shaft? ruined prop.

Its probably fine. Having a aluminum prop really saves your lower unit the shock and damage that a stainless prop can transfer when you strike something.

I am running on a bent propshaft and have been for at least two months. I spin the prop everytime I go out and the bearings feel fine and no sign of leakage of oil. I lucked out and found a original mercruiser alpha gen 2 on ebay for 300 plus 60 shipping. I'm going to be buying me a rebuilt aluminum 21 pitch as soon as I can so I don't repeat this painful lesson.

 

[dieselram94]

Re: Bent prop shaft? ruined prop.

I am going to try to find a way to better hold my dial indicator and get a better reading. How long do you guys think it will live if it is bent?

 

[achris]

Re: Bent prop shaft? ruined prop.

.... Having a aluminum prop really saves your lower unit the shock and damage that a stainless prop can transfer when you strike something.....

I don't know how many times I've heard this said and it's just not true! The material the propeller is made of has absolutely no bearing on the extend of any damage done. I have seen quite a few aluminium props with a few rub marks on the leading edge, and the drive shaft is sheared! or the gears are cracked. I have also seen the exact opposite, a stainless steel prop with the blades folded back so far that they were touching the hub. I was expecting the internals to be like a grenade went off in there.... But no, after stripping the box and checking for cracked gears and bent shafts, it went out with a new prop and that was all the damage sustained. I have also seen a badly damaged ali prop with bent prop shaft....

There is a rubber hub (or plastic in the case of a Flo-torq 2) between the prop blades and the prop shaft... Any shock should be taken by that, regardless of the material of the prop.

Bottom line.... the type and extent of the damage has more to do with the mood of god than the material the prop is made of.....

Chris..........

 

[achris]

Re: Bent prop shaft? ruined prop.

I am going to try to find a way to better hold my dial indicator and get a better reading. How long do you guys think it will live if it is bent?

Maximum allowable runout is 6 thou... If you are trying to hand hold the gauge, forget it! You need to pull the shaft out and set it up on vee blocks on a bench, then measure the runout AT THE CENTRE OF THE SHAFT.... You can not do that with the shaft in the gearbox.

 

[dingdongs]

Re: Bent prop shaft? ruined prop.

get yourself a chartplotter and depth sounder.when in unfamiliar waters dont let the missus take the wheel & rap for mishaps.lets hope ladyluck is on your side this time!!

 

[dieselram94]

Re: Bent prop shaft? ruined prop.

Thanks for the replies everyone. I got the new prop today but haven't had a chance to do anything more with it but I will tomorrow. I guess worst case is I replace the drive with a SEI unit. But I would like to get the rest of our short Maine summer out of this drive.

 

[dieselram94]

Re: Bent prop shaft? ruined prop.

I put the new prop on today and it does seem to have a very slight wobble when spun. I think it might have been like this all along because this prop very lightly rubbed the case in the same spot as the last one ( the inside hub part against the inside of the case) with the first prop I just thought it was some extra thick powder coating on the propeller but now it has done the same thing with another new prop I think it was already bent. So I will put it in the lake weekend after this one and see what happens. Worst case I will buy a complete upper and lower SEI unit, when it fails......if ever.