prop rattle

[nelson edens]

I am new to FloTorque props. Got my first experience this year with a new 4 stroke 115 (pontoon). The prop rattles so bad at idle (in gear), that it sounds like the lower unit is coming apart. Problem is only at idle in gear.

Just bought a FloTorque prop for the Allison. Same thing, but not as bad.

Both of the boats are small shaft Mercs. No problem with fixed hub props.

thanks, Nelson

[pointer]

Some of the smaller 40 - 50 big foot gearcases have a higher torque spec on the prop nut, and I think that 115 does as well. I don't have the spec on hand but can look it up for you if you wish.
On the Allison - not sure.

pointer

[HStream1]

The Flow Torque takes a different Hub washer/spacer than a standard hub. That sounds like your problem Nelson.

http://i465.photobucket.com/albums/rr18/jbcincnc/Flow%20Torque%20washer_zpspv236jro.jpg

[XstreamVking]

The new smaller 4 strokes have a wobbly prop to negate vibration at low speed. A flo tq needs a washer like bud says.....They do not wobble..

[nelson edens]

Really confusing to me. There seem to be 100's of prop hubs. I need part numbers if possible.

The pontoon prop is an Enertia (48-898992-16P). The plastic insert fits really loose in the prop. And the brass sleeve fits loose in the plastic sleeve.

[XstreamVking]

Here's a list of some https://propshopinc.com/Flo-Torq-Hub-Kits-c261/ One at the bottom left of the page says reduces rattle and is for 4 strokes.

[nelson edens]

The reason I bought a 4 stroke is because it was 'quiet'. I don't want to 'reduce' prop rattle, I want NO prop rattle. It seems that I will have to buy a fixed hub prop. It's insane that I have a new quiet motor with a high dollar prop that makes this much noise. Sorry for the rant!!!

[XstreamVking]

My bud has a 150 4 stroke with a rattle prop on it. Never heard a peep out of it....And very little vibration...

[phillnjack]

how are you tightening the prop nut ? as in what poundage on the torque wrench are you tightening the hub nut too ?

[nelson edens]

About 75 ft lbs.

[flabum1017]

The rattle is the nature of the beast, even Merc came out with a service bulletin about it and called it normal. I have seen Yammis and Susuckies do it too.... you can try putting more pressure on the prop by trimming up with the engine. The rattle is caused by the boat getting to it's fastest speed and the inertia of the boat relieves the load to the prop so the engine has no real load and the ss prop is heavy and it's spinning inertia and will "pass up" the boat then as the boat slows the pressure is put back on the prop and the gears slam back together.... clear as mud? Rubber hub props will dampen the gear impact, so you don't hear it. Aluminum props don't tend to do this since they are so light, there is not enough spinning inertia to cause this. Trimming the engine up will put more constant pressure on the prop since it will be trying to push the boat forward and pushing down on the back of the boat at the same time...... just remember to trim back down before you try to jump back on plane.

[nelson edens]

I think that settles it. I will get a fixed hub aluminum prop. After all, it's a 30 mph pontoon boat!!!
Anybody need a new Mercury Enertia 48-898992 16P? (14.7 x 16P) OR trade for 15 spline approx. 15P aluminum pontoon prop ???

[perfmarine1]

The rattle is the nature of the beast, even Merc came out with a service bulletin about it and called it normal. I have seen Yammis and Susuckies do it too.... you can try putting more pressure on the prop by trimming up with the engine. The rattle is caused by the boat getting to it's fastest speed and the inertia of the boat relieves the load to the prop so the engine has no real load and the ss prop is heavy and it's spinning inertia and will "pass up" the boat then as the boat slows the pressure is put back on the prop and the gears slam back together.... clear as mud? Rubber hub props will dampen the gear impact, so you don't hear it. Aluminum props don't tend to do this since they are so light, there is not enough spinning inertia to cause this. Trimming the engine up will put more constant pressure on the prop since it will be trying to push the boat forward and pushing down on the back of the boat at the same time...... just remember to trim back down before you try to jump back on plane.

Yes this /\ remember 4 strokes fire every other time. IMO like flabum said the prop is getting ahead of the clutchdog then the rattle you here is when it slams back against the teeth. It shows up more on sm motors than large. Stick with a light prop.

[staylor]

I have a 21 ft 'toon with 115 Merc 4S. I'm running a stock black max aluminum prop and have no rattle. In comparison, I also have a 17 ft vee hull fishing boat running a 150 Merc 4S with SS props. With a 21 Tempest Plus with the high performance Flo-Torque hub with the forward bushing I get some prop rattle in reverse only. With 23 Trophy Plus with the same Flo-Torque hub with forward bushing I get no rattle. I'm guessing that the exhaust flow over the small hub Trophy Plus is not allowing prop rattle to set up. On your pontoon rig I think you'll be very happy with a plain old aluminum prop.
Doug

[W2F a V-King]

Sure sounds like gear backlash rattle to me.

I had a Yamaha 225 Excell in 1987 that exact noise you describe drove me nuts... It idled so low and the prop was a heavy SS prop. Never had any issues what so ever with it, but the noise was always there...I bumped the idle up just enough to negate that noise.

Done

HTH

[Mr. Demeanor]

Read this:
http://www.thehulltruth.com/boating-forum/604189-hubs-power-tech-s-cush-lok-vs-mercury-s-flo-torq-2-vs-solas-rbx.html#b

[Mr. Demeanor]

Call Ken Reeves at www.propgods.com he will get you squared away with the right hub that wont rattle.

[phillnjack]

Vey interesting read.