Prop Rattle still with Flo-Torq III hub kit - Change to IV hub kit ??

[Canufixit2]

Hi,
Very Quick Summary. ...

2018 Merc 60hp CT on 18 Ft. Pontoon. With my Pontoon I usually ride at min Idle speed. I have a 14"d x 11 Merc Black diamond prop I changed from the flo-torq II hub kit to the Flo torq III and although the prop rattle is Much better, I still get slight annoying rattle at slowest speed (900 ish PRM) and need to up RPM about 300 RPM to prevent rattle ( and just a little too fast for trolling !!).

2 questions ....

1.) can I change to the Flo-torq IV to prevent the rattle or is this a no no / no fix with this engine/prop??

2.) With the Merc Flow-torq III kit - is it Just me - or is the Aft Adapter 878584 lengh too long allowing for sloppy prop fit? I did measure two of these adapter and find they differ in length by about 1/32". Are these lengths Fitted to the specific kit drive sleeve (plastic) length or just drifting due to mfg. tolerances (Plastic drive sleeves length probably varys as well?). Should the Aft adapter (S Steel) be milled down in length to only give a slight slop? Merc says the prop slop is normal and may seem excessive in some fitments. There are multiple Post/discussions on this issue but not concise

 

[Texasmark]

Ping Faztbullet.

 

[QBhoy]

Hi. This is quite a common thing on CT engines. I had it initially with the 115. And especially with the big diameter and heavy tempest plus.
Just be aware that you need a different thrust washer behind the prop with the hub that claims to Eliminate this. Also make sure your hub assembly is fully home in the prop. Also make sure you have tightened the prop but right up too. Not just against the resistance of a tight fitting hub. Think the torque is higher than normal on these usually. Can’t remember without looking it up.

 

[Canufixit2]

How do I ping Ping Faztbullet.

 

[dingbat]

I had the same issue with an Enertia prop on a Flow-Torq hub

Replaced it with a Solas Rubex hub. Problem solved.

 

[Canufixit2]

I'm thinking that quite a few things drove Merc to change from the solid hub .......

- Changes from 2 Stroke to four (each cylinder firing on each rpm, vs every other stroke) Harmonics and vibration changes.
- Changes to the lower units gearing/clutches etc. (command thrust and high HP motors)
- Attempt to reduce number of props to inventory. By changing the hub, less Props need to be stocked to fit more applications.
- 4 strokes with solid hub props transmit shift/clutch noise, motor vibrations much differently. Hub kits help to absorb the shift shocks and prop/motor vibrations differently.
- Some Customers want general all round issues reduced. Others have a specific operating mode that "must" have great performance - i.e., High speed racing vs. Pontoon slow cruising have different performance / noise / vibration needs to the customer.
-

Now, by addressing one or more of the above issues - it causes the other issues to be enhanced. Fix the 4 stroke harmonics in one prop hub design - then it cause louder shift clanking , Prop chatter/rattle is enhanced by some of the Hub kit designs, but clutch shifting is smoother. Tight solid hub kit my fix the prop rattle but transmit more engine vibs/noise.

Seems like Mercury is still hunting for the cure all. In the meantime, they have produced many options on the hubs to address the particular Motor type. Causing confusion to the end user and an inability to properly select the proper prop and hub kit from a catalog/list. Hit and Miss / trial and error and customer frustration is sure to occur with some end users.

So ... I'll continue to read, search, try, and modify and hopefully get "My" best prop/hub kit match.

JMO

SteveC

Other thoughts/inputs most welcome !!

 

[QBhoy]

There haven’t been fixed spline props about for general use for at least a decade or more really.
CT engines aren’t higher HP. Just a step up in gearbox size from what the normal version would be, so bigger props ran. This exaggerates the effect.
enertia ans tempest are both guilty of causing this issue on larger CT gearbox engines, but I’d say the right merc hub, torque and thrust washer is the best answer so far.

 

[Texasmark]

Hi. This is quite a common thing on CT engines. I had it initially with the 115. And especially with the big diameter and heavy tempest plus.
Just be aware that you need a different thrust washer behind the prop with the hub that claims to Eliminate this. Also make sure your hub assembly is fully home in the prop. Also make sure you have tightened the prop but right up too. Not just against the resistance of a tight fitting hub. Think the torque is higher than normal on these usually. Can’t remember without looking it up.

55 ft-lbs on the 75-125, 3 and 4 cylinder engines that normally used the 13-14" diameter wheel.

The rubber cushioned hub, coming of age in the '50's give or take was designed to cushion the mechanics when shifting. Hubs usually lasted the life of the engine. In some applications, where a lot of underwater strikes caused frequent slipping to the point that the hub wouldn't take WOT throttle, you had to re-hub....at a prop shop.

With today's idea, you have a shelf full of props that fit any engine...just install a different hub. sounds great till you get to the part where....upon striking an object, remove the prop and install a new hub and reinstall on engine.....ok, we are back to the days of the shear (er ah drive pin) that seemed to always shear when you needed thrust the most. No thanks.