Previous in Forum: Blind Flange Thickness for Hydrotest   Next in Forum: Where can We get Wet Steam Expander
Close

Comments Format:






Change Mode
Close

Subscribe to Discussion:

CR4 allows you to "subscribe" to a discussion
so that you can be notified of new comments to
the discussion via email.

Close

Rating Vote:







Add Vote
8 comments
Rate Comments: Nested
Circuit Breaker
Guru

Join Date: Jul 2006
Location: CA (Central Arkansas, USA)
Posts: 599
Good Answers: 10

Prop Shaft Run Out

07/13/2012 1:14 PM

My boss let his party barge drift into shore and tore up his prop on a 150 HP outboard. I told him I will go up and check the runout on the shaft. I don't know what the max allowable should be. When I was racing, 40 years ago, if it didn't break the shat, we sent the lower unit to a specialist to be checked. It usually broke the shaft, so it was obvious that it needed to go to the lower unit guy. The prop was usually in a couple of hunderd feet of water, so we had to go to the prop guy, too! I don't remember the brand on my bosses motor, when I go up there I'll get all that so I can check with factory service if it is marginal. I am hoping to get a go/no go because he is asking if he can use it the rest of the season and then send it in. He had a local handiman replace the prop and he said it wasn't "too bad". -- JHF

__________________
 If it's too good to be true, it probably isn't
Register to Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.
KJK/USA
Guru
United States - Member - Member Engineering Fields - Electrical Engineering - Electrical Construction

Join Date: Apr 2010
Location: Mid Western USA - The Corn Belt
Posts: 1439
Good Answers: 58
#1

Re: Prop Shaft Run Out

07/13/2012 1:42 PM

Hey there CB,

Ideally you should have as close to 0 run-out to eliminate the potential for vibration but if my memory serves me, up to .010 on a long shaft and .15 on a short measured just below the nut thread is acceptable turning up to a 14" wheel. (Your Boss's is most likely a long shaft)

I am assuming that the prop was/is aluminum. Outboard props have a rubber bushing (donut) to absorb shock.

Having destroyed many a prop back in my 20 year career of boating, I never damaged a shaft in the process.

Can't tell having not seen the prop but there is a possibility that the shaft survived the impact.

Either set up a dial indicator and check for run-out or if you don't have a dial indicator and with the replacement the handyman put on, take her for a spin.

You will feel any run-out as soon as you throttle up and then can decide if the lower unit needs to be pulled now or at season end.

Hopefully the boss left some adult beverages on board so you don't dehydrate

Regards - KJK

__________________
 The first 5 days after a weekend are always the hardest................................
Register to Reply
Circuit Breaker
Guru

Join Date: Jul 2006
Location: CA (Central Arkansas, USA)
Posts: 599
Good Answers: 10
#4
In reply to #1

Re: Prop Shaft Run Out

07/13/2012 3:05 PM

Thanks! I was thinking around .010. When I first started racing in 1970 the Merc 1250 lower unit was said to have a propshaft that was mild steel inside the housing and stainless outside and they would break at the transition. I pit crewed several boats that broke prop shafts over the years, but I never did. I ran a 1350 that had a different gear ratio than the 1250s and the later 1400 and 1500s. I am pretty sure my boss has a stainless prop and that is what scared me. Thats a lot of weight to be very much off center! Thanks again for the info. I do have a dial indicator and am hoping to pick when to go up there. Its almost 100 miles and I am hoping to get into a camping area and get some R & R (read beer drinking) time while there. -- JHF

__________________
 If it's too good to be true, it probably isn't
Register to Reply
lyn
Guru

Join Date: Oct 2008
Posts: 42355
Good Answers: 1693
#5
In reply to #4

Re: Prop Shaft Run Out

07/13/2012 3:48 PM

It was 105°F two weeks ago when I was there. I hope it has cooled off some.

Better throw in some extra beer and ice just in case.
Register to Reply
Circuit Breaker
Guru

Join Date: Jul 2006
Location: CA (Central Arkansas, USA)
Posts: 599
Good Answers: 10
#7
In reply to #5

Re: Prop Shaft Run Out

07/13/2012 5:15 PM

Ya, and its a dry county, so we'll have plenty of stuff to make a thorough eveluaasssoooonnnnzzzzz.

__________________
 If it's too good to be true, it probably isn't
Register to Reply
KJK/USA
Guru
United States - Member - Member Engineering Fields - Electrical Engineering - Electrical Construction

Join Date: Apr 2010
Location: Mid Western USA - The Corn Belt
Posts: 1439
Good Answers: 58
#6
In reply to #4

Re: Prop Shaft Run Out

07/13/2012 5:08 PM

No Problem.

Even with the SS prop, it should still have the rubber donut between the prop hub and prop.

Hope everything works out for you!

By all means, get some quality drinking R&R time in

__________________
 The first 5 days after a weekend are always the hardest................................
Register to Reply
lyn
Guru

Join Date: Oct 2008
Posts: 42355
Good Answers: 1693
#2

Re: Prop Shaft Run Out

07/13/2012 1:53 PM

If he's going to get it fixed, might as well do it now. Any vibration is not good. It will be transmitted into the welds in the transom and the rest of the boat, not to mention wear on bearings, lower housing etc.

That's not much help, I know.

I solved the problem of boat maintenance by selling mine.
Register to Reply
KJK/USA
Guru
United States - Member - Member Engineering Fields - Electrical Engineering - Electrical Construction

Join Date: Apr 2010
Location: Mid Western USA - The Corn Belt
Posts: 1439
Good Answers: 58
#3
In reply to #2

Re: Prop Shaft Run Out

07/13/2012 2:18 PM

Old and true saying.....The two best days in a boaters life is the day he buys his boat and the day he sells his boat

__________________
 The first 5 days after a weekend are always the hardest................................
Register to Reply Off Topic (Score 5)
Wal
Guru

Join Date: Jun 2011
Location: Phnom Penh
Posts: 4019
Good Answers: 102
#8

Re: Prop Shaft Run Out

07/15/2012 7:15 AM

If it doesn't vibrate the it's probably ok.

100 miles for payed work is not far. Boss is paying for your gas right?

__________________
 Difficulty is not an obstacle it is merely an attribute.
Register to Reply
Register to Reply
Have a Different Question?
8 comments
Copy to Clipboard

Users who posted comments:

Circuit Breaker (2); KJK/USA (3); lyn (2); Wal (1)

Previous in Forum: Blind Flange Thickness for Hydrotest   Next in Forum: Where can We get Wet Steam Expander

Advertisement

Got Something to Say?
Ask a Question
Start a Discussion

Search this Forum
Mechanical Engineering:
Go

CR4 Sections
Aerospace
BioMech & BioMed
Chemical & Material Science
Civil Engineering
Communications & Electronics
Education and Engineering Careers
Electrical Engineering
General Discussion
Instrumentation
Manufacturing
Mechanical Engineering
New Technologies & Research
Software & Programming
Sustainable Engineering
Transportation

Site Directories
Forum Directory
Blog Directory
User Group Directory
RSS Feeds

CR4 Rules of Conduct
CR4 FAQ
Site Glossary

Who's Online (101 right now)
Show Members
Advertisement