Prop Nuts

[bmac]

This doesn't really need to be in the diesel section as I'm pretty sure it applies to all inboard props. I had both props removed, checked, balanced and reinstalled at the beginning of last season. When the boat was hauled at the end of this past season I had a small ding in one of my props so I had the prop shop come and inspect it and make a recommendation. When they came to the boat they suggested it be sent out to be cleaned up. They also said that the prop nuts, as found, were installed in the wrong order. They didn't comment when I reminded them that they did the props last spring. I looked at a new Sea Ray and its prop nuts are installed thinner nut closer to the prop then thicker nut (please no nut jokes). Mine are opposite that. Which order is correct and if you know, why? Lastly, when sending one prop out, even for minor work, should both go out? As always, thanks for the help.

 

[Johnny D]

the skinny nut goes on first.the thicker nut is the lock nut. see the attached link.

http://www.unitedpropeller.ca/propinstall.htm

 

[tobnpr]

The larger nut is the lock nut.
Why? Good question...

I see no need to send out a prop for service that doesn't need it. If the boat's propped right, and there's no vibration or other issues I'd leave it be.

I'm getting ready to do my annual haul-out/bottom job and I need to pick up 100 rpms or so, so I'm going to have them scanned- I've read it's money well spent.

 

[bmac]

Thanks Johnny. North Shore or South?

the skinny nut goes on first.the thicker nut is the lock nut. see the attached link.

http://www.unitedpropeller.ca/propinstall.htm

 

[Johnny D]

Thanks Johnny. North Shore or South?

south shore, freeport

 

[Robski97]

Brian,
I did not forget ur zincs. I called my marina 3 x . The part #'s are there #'s it wont help u so i asked them to tell me ...

40 days til splash.....

 

[topgun1185]

This is right skinny than fat (lock) nut. I always found this intresting since almost any time I look at an inboard boat they arealways on wrong. Next boat show check it out. My MM dealer even didn't know. Great info

 

[geriksen]

Yes, the skinny nut goes on first.
They get put on wrong so often because it is almost impossible to find a proper wrench to hold that large skinny nut while tightening the outer one. You can buy a plumbers wrench but they are very flimsy. So mechanics put the big one on first so their wrench will hold it while tightening the second nut. Then you have a cotter pin that only comes in to play after the nuts have already loosened up. It is an extremely poor design that has somehow survived for many years.
Many times I have thought about coming up with a solution for this.
A specialized wrench?
A castle nut with deep slots so the cotter pin actually keep the nut in place.
A nylock as the second nut?

We find loose props all the time. This should be very simple to fix but the industry does not seem interested.

 

[mrsrobinson]

On the scan or not scan the other prop question, it's always been my opinion, while the boat is out, while you have access to the props and one is going to the shop anyway, take both. It's cheap to have the shop check/test the prop compared to wondering all season "was it true?".

 

[tobnpr]

Since we're talking prop nuts, don't know if anyone else saw it recently but there was a program on one of the sat channels (mega something, maybe) that was about the largest freighter (containers) ever built- in the last year or two. Single diesel engine that had a footprint the size of a tennis court- put together in the freighter- had access doors where you could actually walk INTO the engine's crankcase, oil sloshing around and all- crank spinning- to inspect it. Propshaft was several hundred feet long- and the propeller, built in Germany, was the largest and most expensive ever made at a cost of one million dollars. I couldn't believe that the whole setup was exactly like on our small boats. Threaded propshaft, slid the prop on and then installed the world's largest washer and the world's largest nut to hold it in place. Didn't see a jam nut, tho... Crazy...

 

[tdappleman]

I saw that show - thing did something like 100 rpm's - yes one hundred....

 

[wingless]

They get put on wrong so often because it is almost impossible to find a proper wrench to hold that large skinny nut while tightening the outer one. You can buy a plumbers wrench but they are very flimsy. So mechanics put the big one on first so their wrench will hold it while tightening the second nut.

Many times I have thought about coming up with a solution for this.

A specialized wrench?

My tool kit now includes a set of open-end wrenches that fit the prop nut / jam nut. I also have a cotter pin removal tool to aid pulling that part while holding my breath.

The wrenches weren't cheap, but they were easy to find.

No problemo holding the skinny while snugging the wide w/ these wrenches.

 

[tobnpr]

I've got a packing nut wrench with pretty skinny jaws that would probably work
http://www.westmarine.com/webapp/wc...=true&storeNum=5000&subdeptNum=4&classNum=286

 

[bmac]

Thanks guys. The prop shop does the reinstall after the props are cleaned up. The funny thing is, they installed the props last spring and then told me the nuts are backwards this winter. Not sure if it was the same mechanic though. Anyway, at least I know to check it after the work is done this spring.

 

[bmac]

40 days huh? I'll be a little later this spring, the first three weekends in April are already spoken for :smt089. As for the zincs....I've identified two of them as E-2's, still working on the other, larger four. Thanks.

Brian,
I did not forget ur zincs. I called my marina 3 x . The part #'s are there #'s it wont help u so i asked them to tell me ...

40 days til splash.....

 

[wingless]

On the scan or not scan the other prop question, it's always been my opinion, while the boat is out, while you have access to the props and one is going to the shop anyway, take both. It's cheap to have the shop check/test the prop compared to wondering all season "was it true?".

My props were scanned and tuned to "S" class this year. This was the first tune. I never noticed an issue. I never whacked them.

Before tune, one was Class 1, the other was Class 2.

Both were balanced.

We'll see how they do once splashed.

It was $1,100 for the pair.

 

[tobnpr]

Can you 'splain how to interpret the bar graph?

 

[wingless]

Can you 'splain how to interpret the bar graph?

The plot shows data for each blade on my four-blade prop in a different color: green; cyan; red and violet. The plot shows data for each blade at four radial locations: 0.6; 0.7; 0.8 and 0.9 of the 22" diameter.

For example, on the 0.9 bar graph before the cyan and the violet blades were working against each other.

Also, the mean pitch on the 0.9 before was way less then the rest of the prop.

The short bar graph on the right shows the mean pitch for each blade, as measured at those four locations.

 

[tobnpr]

Got it.
Looks like it was pretty good to begin with- the purple blade being out only .2 at the worst spot.
Let us know if you think it was worth $1,100 after you've run it.

 

[wingless]

Looks like it was pretty good to begin with- the purple blade being out only .2 at the worst spot.

That's correct. The port prop passed Class 2 and the Starboard was better, passing Class 1, prior to any tuning.

Let us know if you think it was worth $1,100 after you've run it.

It will REALLY suck ifin I touch bottom. Most of the cost was bringing these to Class S. As stated, they seemed fine before, so the improvement is likely to be incremental.

What is the typical Class selected for tuning?