Flo-Torq IV and III

[Pescadora]

This is a follow-on to the Enertia thread I started, where somewhere in the posting I mentioned an occassional rattling vibration at idle that does not occur with aluminim props.

The "chugga-chugga-chagga" sound with noticable increase in vibration. Nicking up the idle immediately cancels the effect.

I've been exploring the use of the FT IV hub for my 2005 F150 yam ever since. I've found a source for the parts but they are not returnable, which means you have to do your homework before plunking down the cash.

In the pictures they sent me, it looks like the inner splined collar which rides on the output shaft now extends fully through the delrin insert. The thrust washer appears to have its own collar which rides inside the forward end of the splined collar. In this rig, the forward half of the Delrin spacer engages the square cavity in the prop, while the back half does not. The back half engages only the output shaft. The two halves are mated with titanium rods molded into both sections.

Under power, the titanium bars flex, in effect acting like torsion springs which absorb vibration. The design won awards in the plastics industry.

But the questions for me remain:

1. Do the Yam F150 and the Mercury Verado have identical splined output shafts on the their respective gearcases.

2. Are the thrust washers for both engines are the same.

My engine came from the dealer with a FT II hub kit and a Merc prop. IF the answers to 1 & 2 are both yes, then the FT VI hub kit is a bolt-on.

 

[WillyBWright]

Re: Flo-Torq IV and III

Splines are the same, but I believe the Yamaha shaft is a bit longer. Regardless, they interchange a good deal. The hubs are the same, some hardware is different, mostly the nut and thrust washer. Yamaha's thrust washer has a fishline reel built into it, the Merc does not. If I recall correctly, the Merc thrust washer will rub on the Yamaha gearcase where the fishline reel would fit into the cavity.

 

[Texasmark]

Re: Flo-Torq IV and III

Beins I have been living with the rattle for over 6 months, gonna jump in.

If this new hub you are discussing really eliminates rattle, it has to flex (back and forth) to absorb the variances between the firing of the cylinders and the rotational environment of the prop. That says that when you are at WOT, the ears (so to speak) of the hub are laid back and as soon as you dump the throttle, it will spring forward with the tension released. Is this correct?

If so great, ought to work. If not someone is blowing smoke. :%

My 2c.

Mark

 

[walleyehed]

Re: Flo-Torq IV and III

Mark, I have 3 flo-torq IV's now and have reamed 2 of them out to fit my rude and My prop-man's Rude.
With it tightly installed on my shaft, the prop moves ever so slightly without the hub moving.
The Merc engineers tell me this is how they addressed the clanking rattle at Idle...sounds oposite to me, but they say it'll work....snow here and single digits last night so maybe next week I'll put'r on the water and see.

 

[Texasmark]

Re: Flo-Torq IV and III

Thanks Ken.

I am convinced that the shift setup is the culprit. On the Mercs (midrange anyway.....tested several at a dealership besides my own) you can push on the prop and it and the shaft will move forward (spring loaded) about 0.100 inch, and pop back when released.

Since Merc uses a shifter cam at the front of the gear train (in front of the front propshaft support bearing) and this cam pushes on a plunger filled with 3 balls and a spring which position the clutch dog, I'm betting that more tension in that spring (or adding a 4th ball) would overcome the problem by forcing the dog's teeth to remain in the drive gear's teeth better. This would solve the problem.

It's just a theory and makes sense to me. I don't have anyone at Merc, that's knowledgeable about the design of their lower unit that could think through this, or has BTDT and knows what will and won't work and why, and why the current tension setup is what's used in production.

In short, why wouldn't more tension work; what would it hurt? Possibly, when they came up with this design back in the '60's this design (some engineer's guestimate) worked and they stopped designing and started production........never changing since as it worked and didn't cause any problems.

Maybe no one investigated why more tension wouldn't work for the heavier, high pitched props that are popular nowadays.

It's too much trouble for me to trial and error this thing since the lower unit would have to be gutted for each test configuration and if I screwed something up, BOOM :%

Any ideas for folks to contact? email would be the best route as I wouldn't have to chase them down to talk.

Thanks,

Mark

 

[WillyBWright]

Re: Flo-Torq IV and III

It's not a matter of how far the shifter slides. The cogs are fully mating. Your motor doesn't run smooth at all, especially at idle. The crankshaft is constantly slowing down with compression and speeding-up with combustion. A V-6 slows and speeds 6 times each revolution. Graphed-out, you would have something closer to a sine wave than a straight power line.

What's happening down in the gearcase is that the mass of the propeller keeps it turning constantly...the old object in motipn tends to stay in motion thing. Graphed-out, it would be straight line. So every time the crankshaft slows down, the mating surfaces of the cogs form a tiny gap as the prop continues it's constant spin. When the sparkplug fires and speeds-up the crankshaft, the cogs slam together. That's the noise you hear. At idle, those speed-slow cycles are much more pronounced than at higher RPMs.

It sounds awful, but it's not generally destructive since the power at idle is so low. It is much more noticable with stainless props than aluminums because the added weight (mass) keeps the stainless prop spinning smoother when the gap forms and then resists speed-up when the cogs slam together again. The torsion rods on the FloTorq IV absorb that slamming.

I wouldn't advise trying this at home, but imagine pushing a car with an SUV. Slow down the SUV and you get a gap between the vehicles. Accelerate to resume pushing and there's a bump. Now imagine that the pushed vehicle is a truck. The bump is more like a jolt.

 

[Tail_Gunner]

Re: Flo-Torq IV and III

Here's a good blurb... http://www.designnews.com/article/CA6345870.html

 

[Texasmark]

Re: Flo-Torq IV and III

Thanks Tail Gunner but that's not the issue. I did however, assume what the article verified and that was that the Merc IV did have a torque deflection on it when at WOT. My shifting clunk is quite low.

Willie hit the nail on the head and I totally agree with his analogy. I assumed this all along and talked months ago of the flywheel being a bit light for the whack of the piston but I got shot down on that. I used the analogy of the 2 "bucket cylinders" on Johnny Pop tractors and the mass of the flywheel that kept her smooth as silk......well sorta.

I guess, now that I read Willie's reply and think some more about it, that the spring would have to really be a wallapaloozie to be able to keep the gears engaged against the torque of the prop.

The other thing that I think adds to the problem is that the 90 hp 3 cyl has larger cylinders than other 3 cyl engines I have owned and that bigger bang surely adds to the whack that is causing the noise......in addition to this prop being 24" and others never got over 19".

Thanks for your replies and I'll put this subject to bed.

Mark