Multiple Spun Hubs

[edc413]

I have spun the hub on my port engine 2 times in the past month. Neither time do I believe I hit anything. Just cruising along and it gave. Boat is a 28' Pursuit with twin 200 HDPI Yamaha's counter rotating. I guess my question is, does anyone have any input into why this may be happening? Could it be caused by excess cavitation / improper trim?

 

[gcboat]

Re: Multiple Spun Hubs

If you've had that same prop repaired twice by the same prop shop sounds like a shoddy repair to me. Take a real good look at it - if no dings, dents or whatever then I would look for someone else to fix it.
Cavitation and trim really have no issues with a hub spinning. Take it back to the previous repair shop - I'd love to hear their side of the story.
Hard to believe that a new prop would fail twice in on e month and on the same motor. My thoughts !

 

[marine4003]

Re: Multiple Spun Hubs

If you've had that same prop repaired twice by the same prop shop sounds like a shoddy repair to me. Take a real good look at it - if no dings, dents or whatever then I would look for someone else to fix it.
Cavitation and trim really have no issues with a hub spinning. Take it back to the previous repair shop - I'd love to hear their side of the story.
Hard to believe that a new prop would fail twice in on e month and on the same motor. My thoughts !

BINGO!!

 

[5150abf]

Re: Multiple Spun Hubs

Were these new props or repaired, you don't say.

I am on my 3rd lower unit so I have hit ALOT of stuff but I have never once spun a hub.

A good prop shouldn't spin because of vibration or anything else, certainly not anything you are doing, as stated, bad repair or bad prop, either way get your money back.

 

[edc413]

Re: Multiple Spun Hubs

A couple answers. There props were recently (a few weeks ago) reconditioned. They are stainless steel 4 blade props and at WOT both engines rev to 5500 RPMS. Which is at the top of Yamaha's suggested 4500-5500 range.

I also misspoke when I said spun 2 times... I guess actually it was 3 times. The first time I noticed some dings so I sent the props for reconditioning when they came back I was told the 1 hub was also bad and it was fixed.

I ran it for a few weeks and the same prop went bad again. This time it was fixed by a different shop. Fix number 2.


Ran it a few more weeks and now is broken again.

Sounds unlikely that 2 different prop shops did a bad repair job so that is why I am asking if anything else could be the cause.

 

[edc413]

Re: Multiple Spun Hubs

Was talking to a Yamaha mechanic about my multiple spun hubs. He looked at the prop and said I had cavitation burns on the prop. He thinks perhaps cavitation is heating the prop causing the hubs to go bad. Does this make any sense?

 

[CharlieB]

Re: Multiple Spun Hubs

How many hours on this engine?

How many Hours on this impeller?

Merc has had an occasional problem with exhaust temps, lack of cooling water mixing into the exhaust stream and melting water pumps. I'm wondering if you could have excessive exhaust heat contributing to this hub problem. Hub running just a bit too warm, then add anything else into the equation and the hub relaxs just enough to fail.

 

[Dhadley]

Re: Multiple Spun Hubs

CharlieB is right on. Some of the Yamaha HPDIs have pretty high exhaust temps and can burn hubs easily. We see it more often on 225s and more on 250 / 300s. There is actually a specific hub the prop shops should be using that's different than the standard hub. The ultimate answer is to get away from the old pressed in hub and go to the square bore props and use the replaceable hub system like the Flo torq system.

How is that motor running? A little down on power compared to what it once was? It's not unusual for those running with that high of an exhaust temp to burn a tuner too.

 

[CharlieB]

Re: Multiple Spun Hubs

The Merc 'fix' is to slightly enlarge the water outlet holes in the adaptor plate to provide additional flow into the exhaust stream.

May be a possibility here.

J/E once drilled at 1/16 hole in the side of the lower transfer tube to direct a cooling stream onto their water pump to cure a melting problem from exhaust heat.

Before I did either I would recommend installing a water pressure gauge an know base pressure before any mods.

 

[edc413]

Re: Multiple Spun Hubs

Thanks for the help guys. Engines (2005) have 250 hours on them (75 this season). Unknown hold old the impeller is. Just got the boat a couple months ago. Water pumps seem to be running fine. No engine alarms. Power seems the same since I got the boat.

I guess this is a novice question, but why would one engine/exhaust run hotter than another? Is that something that needs to be looked at?

 

[CharlieB]

Re: Multiple Spun Hubs

It's been know to happen, that hitting a rotted log, or part of, pieces of that soft wood can be picked up and run thru the cooling system, accumulating and restricting water flow.

Dragging the bottom, beaching, sand gets passed thru the system and accumulates.

Once the water drain holes in the adaptor plate are restricted enough, exhaust temps begin to climb, shortly followed by climbing engine temps.

Which of the above applies to you?

Change those impellers AT LEAST every other year, if not every year. It's cheap enough insurance against toasting a motor. Learn to DIY.