Prop shaft bent?... or mis aligned? VolvoSX

[gregtay]

Hi all. first post.
Question... last year i backed my boat into a cement wall in my garage... the outdrive was turned and it was up.. took a hit (alum prop took most of the hit.) Wasn;t going fast, but it was a cement wall.

a few weeks later i noticed oit leaking from the outdrive. turns out a broke a seal (not surprised.) I expected more damage but they said everything was fine... but...

When i try to install my original Volvo prop i rubs ont he out drive. It only rubs on the left side. I can fully install the prop but if you spin it you can feel/hear it rub. (i had been running a different prop with more clearance where it meets the outdrive... so i didn't notice anything till now.)

So it seems that my prop shaft is actually not aligned with my outdrive. If it was bent i would expect the "rubing" to rotate with the prop. But in my case it seem the shaft is simply not centered in the drive.

Thoughts on what could cause this? Thanks for your time.

1999 Monterey Montura 196 Volvo 5.0 SX

 

[DJ]

Re: Prop shaft bent?... or mis aligned? VolvoSX

When you backed it into a concrete wall, you bent-SOMETHING.

Prop shafts are very resilient to forces generated, normally, while boating. Backing up is NOT one of them.

My guess, from description received, you bent your prop shaft. Time for a dealer visit.

 

[gregtay]

Re: Prop shaft bent?... or mis aligned? VolvoSX

Thanks. That is what i figured.. but I guess i would think that the place where it rubs would rotate with the shaft... vs. just being always on the left. The dealer looked at it right after i did it and said i just broke a bearing... but obviously they missed something.

 

[bruceb58]

Re: Prop shaft bent?... or mis aligned? VolvoSX

I would think that if you bent your prop shaft, you would have a wobble which would cause the prop to rub on all sides. Seems to me that you damaged your bearing housing.

 

[tommays]

Re: Prop shaft bent?... or mis aligned? VolvoSX

i think you may have mixed Up the thrust washers that go in front of the prop

different brands of props use different ones to provide the correct clearance

Tommays

 

[gregtay]

Re: Prop shaft bent?... or mis aligned? VolvoSX

i think you may have mixed Up the thrust washers that go in front of the prop

different brands of props use different ones to provide the correct clearance

Tommays

Actually i thought the same... and originally that was the problem. But i went and ordered a new Volvo thrust washer (the one be goes between the drive and the prop.) Certainly less rubing (since the washer actually centers the prop)... but i still have rub. Good thinking though... because that was a problem.

 

[Limited-Time]

Re: Prop shaft bent?... or mis aligned? VolvoSX

Is the housing egg shaped by chance? Or is there a prop shaft alingment issue?

 

[gregtay]

Re: Prop shaft bent?... or mis aligned? VolvoSX

Is the housing egg shaped by chance? Or is there a prop shaft alingment issue?

How would i know if the housing is egg shaped? Is it possible to adjust the prop shaft alignment? There is no free play anywhere in my unit... what every is "not right" is just slightly "not right". (if it was obvious i would think my dealer would have figured it out when he had the drive apart replacing the seal/gasket.)

 

[Reel Poor]

Re: Prop shaft bent?... or mis aligned? VolvoSX

Remove the prop and check the shaft runout (wobble) with a dial indicator. If you don't have the tools to do it, with take it back to the dealer that did the repairs and have them do it. If the shaft is bent this will show the problem.

 

[DHPMARINE]

Re: Prop shaft bent?... or mis aligned? VolvoSX

Dial indicate the shaft.If is okay (under .005) I have seen props slightly off,rubbing the larger diameter of the gearcase. After a short run not a big problem.

DHP

 

[Bondo]

Re: Prop shaft bent?... or mis aligned? VolvoSX

When i try to install my original Volvo prop i rubs ont he out drive.

Is this the prop that was on the drive when you backed into the wall,..??.......

Is the Hub still Square with the Prop's Body,..??.....

 

[Don S]

Re: Prop shaft bent?... or mis aligned? VolvoSX

To cause the prop to rub the housing, you would have to have a lot of bend in the shaft. You should be able to see if you have a bend by using a ruler and turning the shaft. Touch the ruler to the cavitation plate and hold it close to the and by eye watch the center of the shaft as you turn it by hand and see if it moves from a point on the ruler. A dial indicator would be the best thing to use, but for the amount of bend needed would be visable.
I would bet you have a prop hub problem it it's the original prop. Assuming it was repaired, did they repair or check the hub also? Have you tried another prop on it to see if it rubs?

 

[gregtay]

Re: Prop shaft bent?... or mis aligned? VolvoSX

When i try to install my original Volvo prop i rubs ont he out drive.

Is this the prop that was on the drive when you backed into the wall,..??.......

Is the Hub still Square with the Prop's Body,..??.....

No, different prop. The prop that was on the drive when it hit the wall never had a problem (the damage was minimal to the prop and i had it repaired.) That prop (Merc 4 blade) had a lot more clearance when it fit into the drive... so i never rubbed.

 

[gregtay]

Re: Prop shaft bent?... or mis aligned? VolvoSX

To cause the prop to rub the housing, you would have to have a lot of bend in the shaft. You should be able to see if you have a bend by using a ruler and turning the shaft. Touch the ruler to the cavitation plate and hold it close to the and by eye watch the center of the shaft as you turn it by hand and see if it moves from a point on the ruler. A dial indicator would be the best thing to use, but for the amount of bend needed would be visable.
I would bet you have a prop hub problem it it's the original prop. Assuming it was repaired, did they repair or check the hub also? Have you tried another prop on it to see if it rubs?

I just spent about 1 hr with a ruler and my prop shaft... it's straight and true. I have zero wobble or deflection. I tried many different things and it spins round. (yeah)

So i happen to have an extra prop identical to the one i ahve been messing with. I tried it last night and had the same rubbing issue.... but tonight i tried it again (this time i actually tightened the prop nut.) turns out it has not clearance issues and everything is good. So I am guessing my old prop (and it is about 6 yrs old) has a worn hub. So all of this for nothing... or at least i hope. I will drop the boat in the water tomorrow and double check there is no rubbing (easy to tell.. the black paint will be worn off the prop where it rubs.)

Thanks all for your suggestions... you saved me a trip to the boat doctor (and he is expensive!)

I am amazed at how close the clearance is between the prop and the drive.... guess everything needs to be perfect.

 

[Don S]

Re: Prop shaft bent?... or mis aligned? VolvoSX

I am amazed at how close the clearance is between the prop and the drive.... guess everything needs to be perfect.

Basically, you're right. It does need to be perfect. The prop is designed to fit very close to the housing so exhaust gasses go out the hub of the prop, and not around the prop at the housing. That would cause air hitting the blade and cause ventilation of the prop.

 

[gregtay]

Re: Prop shaft bent?... or mis aligned? VolvoSX

I am amazed at how close the clearance is between the prop and the drive.... guess everything needs to be perfect.

Basically, you're right. It does need to be perfect. The prop is designed to fit very close to the housing so exhaust gasses go out the hub of the prop, and not around the prop at the housing. That would cause air hitting the blade and cause ventilation of the prop.

That explains why my 4 blade Merc prop ventilated (alot!) in the turns. Never really liked the prop for that... but it had a great hole shot and performed well at wakeboard speeds. The merc prop has a much smaller hub side (external dimensions) and i can see how a lot of exhaust would have come out around the prop.

So that leads me to another question... how do you know the exterior hub size when purchasing a prop?

 

[Bondo]

Re: Prop shaft bent?... or mis aligned? VolvoSX

There's 4" Gearcases,+ 4,1/2" Gearcases..........
They Both use the same Propshaft dimensions..........
For Merc.s anyways....

The Small 1s are on Outboards,+ use the Smaller Props.....

"The merc prop has a much smaller hub side (external dimensions)"
It's Probably an Outboard Prop..........

 

[gregtay]

Re: Prop shaft bent?... or mis aligned? VolvoSX

There's 4" Gearcases,+ 4,1/2" Gearcases..........
They Both use the same Propshaft dimensions..........
For Merc.s anyways....

The Small 1s are on Outboards,+ use the Smaller Props.....

"The merc prop has a much smaller hub side (external dimensions)"
It's Probably an Outboard Prop..........

Guessing your right. grrrr... guess you can't trust the boat shop. Oh well.. the prop still served it's purpose for a few years.