Propeller Rubber Hub Damage

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
Oldslowandugly
Posts: 414
Joined: Fri Jan 15, 2016 11:19 pm
Location: Queens NY

Propeller Rubber Hub Damage

Postby Oldslowandugly » Tue Sep 10, 2019 10:50 am

On a 1993 Evinrude 48SPL with a stainless steel propeller, while chasing Bluefish I ran across a mud-sand bar at full speed. The engine halted twice before I cleared the bar.

The propeller rubber hub is supposed to slip so the gear case does not get damaged, and I think it did slip.

My only prior experience has been with old dried out hubs that once they slip they are done for. This hub I had replaced with a new one last year.

If the rubber hub slips is it still good?

Tomtep
Posts: 12
Joined: Fri Aug 12, 2016 9:56 pm

Re: Propeller Rubber Hub Damage

Postby Tomtep » Tue Sep 10, 2019 12:42 pm

Time to have the rubber hub replaced again. There needs to be zero slippage.

Oldslowandugly
Posts: 414
Joined: Fri Jan 15, 2016 11:19 pm
Location: Queens NY

Re: Propeller Rubber Hub Damage

Postby Oldslowandugly » Tue Sep 10, 2019 5:57 pm

So they are expendable. I didn't know that. I ran [the engine and the boat got] on plane; the rubber hub seemed OK.

User avatar
Acassidy
Posts: 136
Joined: Sat Nov 14, 2015 10:25 pm
Location: Galveston, Texas

Re: Propeller Rubber Hub Damage

Postby Acassidy » Tue Sep 10, 2019 11:34 pm

The hub is not supposed to ever slip. The force going WOT is way more than changing gear. Once the hub slips once it is gone forever. Have the prop shop press a new one in there for you. They are supposed to be sacrificial to save the lower unit when striking something.
Archie

flymo
Posts: 189
Joined: Thu Oct 22, 2015 2:58 pm

Re: Propeller Rubber Hub Damage

Postby flymo » Wed Sep 11, 2019 6:33 am

Unless you hit a rock, the hub may be fine. If it takes off OK on a fast start I'd be tempted to leave it alone. You may have ingested some mud, so keep an eye out for cooling system problems.

jimh
Posts: 7125
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: Propeller Rubber Hub Damage

Postby jimh » Wed Sep 11, 2019 8:29 am

To know the exact condition of the rubber hub on the propeller on you boat is impossible. To know how the rubber hub reacted to whatever occurred on the passage across the shoal is impossible.

To tell if the hub is slipping, remove the propeller from the propeller shaft. Examine the forward face of the hub. Look for circumferential scratches or other indicators that there was a difference in rotational speed between the propeller and the propeller shaft.

Oldslowandugly
Posts: 414
Joined: Fri Jan 15, 2016 11:19 pm
Location: Queens NY

Re: Propeller Rubber Hub Damage

Postby Oldslowandugly » Wed Sep 11, 2019 10:00 am

I just re-read the factory service manual. Oddly it does not mention the rubber hub or what to do if the prop strikes something. I took the steel prop off and replaced it with a spare aluminum one I had. I can't leave that one on because it has one inch too much pitch and the motor struggles to reach full rpm. I ordered an identicle new stainless steel prop but it will also have one inch too little pitch like the original. I had the current steel prop cupped at the prop shop so that it acts like the unavailable in-between pitch my boat requires.When it arrives I will take it to the prop shop to get cupped. I will also bring the current prop and let the shop guy put it on his equipment. He will test it and see if it is usable or needs re-hubbing. When he cupped that first prop he advised that the rubber was "squishy" but still usable for the season. He said to go ahead and use it and if the motor likes it then to bring it in over the winter for a new hub. That is what I did and that is why I was wondering if the new hub could stand the impact slipping or must be replaced. As Jim mentioned, I have no way of knowing if it actually slipped. Besides losing a lot of paint there are no dings or scratches so maybe it missed any rocks. I will let the shop test it.

biggiefl
Posts: 326
Joined: Thu Jul 11, 2019 1:31 pm
Location: south Tampa Bay area
Contact:

Re: Propeller Rubber Hub Damage

Postby biggiefl » Wed Sep 11, 2019 11:26 am

Just because you hit bottom does not mean you damaged the hub. If it drives the same as before you hit the bottom you are OK and so is the hub. Why would you buy a new SS prop even if you did ruin the hub? You just have a new hub put in for $40 or $50. This does not make sense as the 1yr old hub is probably much stronger than the old one in the aluminum prop. If I replaced the hub for every time I struck bottom, I would be broke. I have ripped off blades and not spun the hub. It is not only "sacrificial", it helps reduce vibrations, etc being rubber. They are a LOT stronger than you think.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll:

Oldslowandugly
Posts: 414
Joined: Fri Jan 15, 2016 11:19 pm
Location: Queens NY

Re: Propeller Rubber Hub Damage

Postby Oldslowandugly » Wed Sep 11, 2019 4:29 pm

I hope you are correct. I will let the prop guy test it. He puts it in a jig and measures the amount of torque it can take before slipping. This prop was badly pitted because the previous owner didn't bother to fix the $800 tilt assist. The lower unit sat in salt water all season long. I filled the pits with Marine Tex, sanded it smooth, and epoxy painted it. Worked OK but I grabbed a new one simply because when I was looking around I saw that the stainless steel props are discontinued by Bombardier. Aluminum is available but I need stainless so I can get it cupped. The few vendors still selling the SST props are asking cutthroat prices. I scored an NOS one cheap enough to re-hub it if necessary and still come out ahead.

biggiefl
Posts: 326
Joined: Thu Jul 11, 2019 1:31 pm
Location: south Tampa Bay area
Contact:

Re: Propeller Rubber Hub Damage

Postby biggiefl » Thu Sep 12, 2019 11:27 am

Ah, that makes sense.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll:

Oldslowandugly
Posts: 414
Joined: Fri Jan 15, 2016 11:19 pm
Location: Queens NY

Re: Propeller Rubber Hub Damage

Postby Oldslowandugly » Thu Sep 12, 2019 5:28 pm

The new propeller arrived. It is spotless. In the future I will take both [the old propeller that was suspected of being damaged and new spotless propeller] to the propeller shop. I will [post an article that reveals if] the old propeller [was actually damaged when the boat was run over the shoal at speed]. I [bought the] new propeller [because] I have no idea of the history of the old propeller. It may have been fixed sometime in the past, The blades may have been cut down to remove damage.

[The old propeller possibly having been reworked in the past] would explain why engine speed over-revved so much [when using the old propeller, and] yet the pitch of the old propeller is only 2-inches less than the aluminum propeller.

jimh
Posts: 7125
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: Propeller Rubber Hub Damage

Postby jimh » Thu Sep 12, 2019 8:00 pm

What will happen to the new spotless propeller when you take it to the propeller shop?

Oldslowandugly
Posts: 414
Joined: Fri Jan 15, 2016 11:19 pm
Location: Queens NY

Re: Propeller Rubber Hub Damage

Postby Oldslowandugly » Fri Sep 13, 2019 11:45 am

The propeller shop will cup the blades of the new 15-pitch propeller. Then it will act like a 16-inch-pitch propeller which no one produces.

My original problem was that the 15-inch-pitch propeller allowed the engine to easily over-rev a lot, to almost 7,000-RPM. Yet a 17-inch-pitch propeller would cause the engine to struggle to reach 5,000-RPM. The engine operating range is 4,500 to 5,500 and the cupped 15-inch-pitch propeller does that perfectly with a maximum engine speed of 6,000-RPM. The SPORT 15 jumps right up on plane and scoots along at 5,000-RPM effortlessly.

Before I do that I need to test the new propeller against the old un-cupped one. If the new one operates the same as the old one before cupping then the old one has not been modified. But if the new one acts like the now cupped old one then I can assume the old one was modified.

biggiefl
Posts: 326
Joined: Thu Jul 11, 2019 1:31 pm
Location: south Tampa Bay area
Contact:

Re: Propeller Rubber Hub Damage

Postby biggiefl » Fri Sep 13, 2019 2:46 pm

If the range is 4500-5500 why are you getting 6,000--RPM?
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll:

Oldslowandugly
Posts: 414
Joined: Fri Jan 15, 2016 11:19 pm
Location: Queens NY

Re: Propeller Rubber Hub Damage

Postby Oldslowandugly » Fri Sep 13, 2019 6:30 pm

That is at WOT. Best I can do. Even if I bring a big butted friend it does 6000. I don't mind because it has enough grunt to lift the boat even with a load. It won't explode just because I accidentally hit 6000.

biggiefl
Posts: 326
Joined: Thu Jul 11, 2019 1:31 pm
Location: south Tampa Bay area
Contact:

Re: Propeller Rubber Hub Damage

Postby biggiefl » Mon Sep 16, 2019 10:33 am

No it won't explode but you should not have your boat propped to hit 500rpm over the redline.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll:

Oldslowandugly
Posts: 414
Joined: Fri Jan 15, 2016 11:19 pm
Location: Queens NY

Re: Propeller Rubber Hub Damage

Postby Oldslowandugly » Mon Sep 16, 2019 12:43 pm

That's the problem. None of the available props will get me EXACTLY in my range. The 15-pitch propeller over-revs wildly and the 17-pitch propeller makes the engine struggle to get to 5,000-RPM. One would assume I need a 16-pitch propeller, but none are available. Best I can do is get the 15-pitch propeller cupped so it acts like a 16-pitch prop.

I guess if I had the propeller shop put a more severe cup on the blades it might bring it down some but there is a limit to what they can do without ruining the prop.

Right now it is muggy and buggy and I hate working like that. The weather is suppose to cool off a lot so I will take the new prop for some testing.

jimh
Posts: 7125
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: Propeller Rubber Hub Damage

Postby jimh » Mon Sep 16, 2019 1:27 pm

OLDSLOW'--thanks for the clear explanation.

That the engine speed is so sensitive to propeller pitch is quite interesting. You report the 15-pitch lets the engine rev to almost 7,000-RPM, and the 17-pitch limits the engine to 5,000-RPM.

It seems like the two-inch change in pitch is causing almost a 2,000-RPM change. Usually we think a two-inch pitch change brings about a 500-RPM change.

Oldslowandugly
Posts: 414
Joined: Fri Jan 15, 2016 11:19 pm
Location: Queens NY

Re: Propeller Rubber Hub Damage

Postby Oldslowandugly » Mon Sep 16, 2019 3:06 pm

Jim- yes that does seem odd. That is why I am going to test the new un-cupped 15" prop and see how it performs. It may be the "right" prop all along. If the old 15" one was cut down that would explain everything. We shall see.

I also had this problem with a 1985 Evinrude 30-HP that was on my 18-foot aluminum skiff. One prop was too little pitch and the next was too much. In that instance the in-between pitch prop WAS available from SOLAS. It worked perfectly. No such luck with this 48SPL.

jimh
Posts: 7125
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: Propeller Rubber Hub Damage

Postby jimh » Tue Sep 17, 2019 8:24 am

Based on the reported outcomes with changing propeller pitch on smaller horsepower engines, that may explain why often in these lower pitch ranges the pitch increments are only in 1-inch changes.

biggiefl
Posts: 326
Joined: Thu Jul 11, 2019 1:31 pm
Location: south Tampa Bay area
Contact:

Re: Propeller Rubber Hub Damage

Postby biggiefl » Tue Sep 17, 2019 12:59 pm

I had a 15' Sport with a 48spl and I ran a 17". I had another 15' sport with a 2cyl 60hp that ran a 19". With my other 15' sport with a 3cyl 70 I ran a Suzuki 20". It depends on the boat and the prop manufacturer.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll:

Oldslowandugly
Posts: 414
Joined: Fri Jan 15, 2016 11:19 pm
Location: Queens NY

Re: Propeller Rubber Hub Damage

Postby Oldslowandugly » Tue Sep 17, 2019 7:58 pm

I have probably over-loaded this Sport. When I first tested it the hull was pretty bare. Just a center console and a cooler seat. I was almost scared at how fast it went. Then I went about customizing it for my kind of fishing and stuff. Now it has the fully loaded console, cooler seat (full of stuff), full stainless railings, stainless Bimini top, forward swivel seat, battery box under that, a 5' x4' mahogany hinged rear bench with two swivel seats, two 6 gallon gas tanks, two large tool/tackle boxes, two oars, and other sundry necessities. It all adds up and weighs a lot for such a small boat. But I accept the weight penalty because I use it only for fishing and everything is indispensable. Tomorrow I test props and will report back.

Oldslowandugly
Posts: 414
Joined: Fri Jan 15, 2016 11:19 pm
Location: Queens NY

Re: Propeller Rubber Hub Damage

Postby Oldslowandugly » Wed Sep 18, 2019 7:51 pm

I installed the 12-3/4 x 15-pitch propeller. Here is the results: IT IS PERFECT.

The engine speed range is from 4500 to 5500-RPM. The boat leaps right up on plane, and settles in at 5,000-RPM. That is the "sweet spot.”

If I push it I can get [the engine speec] to 6000-RPM but no need to. It simply purrs along at 5000. It will maintain plane at 4000 rpm and at 2000 I can easily navigate "NO WAKE" zones without a worry. In fact 2000 and 5000 rpm seems to be the optimum operating points for this boat. So this proves that the old 15" prop that came with the motor had to have been "re-conditioned" at some point. Now that I have an untouched stock prop to compare it to I can now say that the old prop acted more like a 13" pitch. Getting it cupped made it act like a 14" pitch and that is why I could get the motor up past 6000 rpm so easily. This NOS prop seems to have been made around 1985 so it is as old as the boat. Paperwork in the box says it is a factory cupped prop. If the old one was also factory cupped then when they rebuilt it they probably ground off the edge to eliminate dings and chips. That not only reduced the diameter but it also eliminated the cupping. So my getting it cupped merely brought it back to something like a 14" pitch. I wish I had been told the facts about this old prop. I would have just bought a new one way back then and avoided all this drama.

biggiefl
Posts: 326
Joined: Thu Jul 11, 2019 1:31 pm
Location: south Tampa Bay area
Contact:

Re: Propeller Rubber Hub Damage

Postby biggiefl » Thu Sep 19, 2019 9:55 am

[The boat is] still under propped if [the engine can accelerate] to [6,000-RPM].
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll:

Oldslowandugly
Posts: 414
Joined: Fri Jan 15, 2016 11:19 pm
Location: Queens NY

Re: Propeller Rubber Hub Damage

Postby Oldslowandugly » Thu Sep 19, 2019 8:36 pm

Perhaps but I can carry a load better. Just today I had my Son-in-law and Grandson out fishing. [The Evinrude 48 SPL engine] still hummed along at 5,000-RPM easily.