Shift clunk and Flo-Torque hubs

[Bigjohn1]

I have an '04 Merc 115efi 4-stroke running a a Trophy Plus 4-blade prop. The loud clunking noise when going into gear is enough to make me want to switch back to an aluminum prop:^

I am using the Flo-Torque II hub but have been advised that switching to the later Flo-Torque III will quiet the clunk down. My idle is set correctly and not too high, also, the motor is in prestine condition so lower unit gear wear is not a likely cause. How do I get rid of the anoying clunk short of switching back to an aluminum prop?

 

[JUSTINTIME]

Re: Shift clunk and Flo-Torque hubs

sounds like u need to adjust your shift shaft
are u slowly putting into gear?

 

[Bigjohn1]

Re: Shift clunk and Flo-Torque hubs

Shifts are quick and deliberate. Shift mechanism at the front port side of the powerhead is adjusted properly.

 

[JUSTINTIME]

Re: Shift clunk and Flo-Torque hubs

hubs have nothing to due with the clunking
bother fwd and rev gears move
when the clutch dog engages either gear that is when the prop shaft spins
either they are not shim correctly or u have wrong shift shaft height or worn gears or clutch dog

 

[Smig]

Re: Shift clunk and Flo-Torque hubs

Bigjohn - I remember reading something about clunking on the props forum. You may want to look over there - try this thread

 

[Bigjohn1]

Re: Shift clunk and Flo-Torque hubs

JUSTINTIME, thanks for your help. I'm not exactly saying a hub is main culprit but its no secret the heavy mass of an ss prop will have more of a clunk than a light aluminum one on this particular gearcase. Actually, Smig's link above was very informative and Merc suggests doubling the torque value on Flo-Torque II hubs to help out (thanks Smig for the link). I have asked the originator of that thread to comment here. Thanks to all.

 

[Texasmark]

Re: Shift clunk and Flo-Torque hubs

I never had a marine engine that didn't clunk to some degree going into gear and over my 50 years of boating I have had a dozen or so and half were new when purchased. It has to, you are putting metal onto metal and there is resistance; the prop. If you read sales brochures from when outboards first got shifters www.old-omc.de for example), part of the reason for going to the rubber hub was to cushion the shock.....hence clunk.

The lighter the prop and shallower the pitch the less resistance to the shift and lower the noise. My current engine has had 4 props on it since I bought it in December of last year. I guarantee you that the pitch and weight of the prop have a profound effect on clunking. In addition, the highest pitched SS, (13 1/2 x 24P) even does the "clutch dog rattle" at low rpm's.

The engine is an '02 with very few freshwater hours, never been in a marina, and has new lube in the gearbox; the old came out clean as a whistle, so don't tell me that I have a problem with it being worn out and that's causing the noise.

Mark

 

[walleyehed]

Re: Shift clunk and Flo-Torque hubs

Mark is correct...
The problem is most evident in Merc 3-cylinder applications, but does show up in some others as well.
It IS NOT a wear factor, it is simply the combination of gear ratio, number of cylinders and the timming between ignition cycles causing the slowing effect of the flywheel at basically no-load RPM settings. This condition is not harmful, yet very noticable on some set-ups...with the advent (re-birth) of the 3 cylinder engines and the multi-piece hubs, it is something that will be with us unless you use the flo-torq III, which is good to 115HP. Infact I believe it was developed for this reason.

 

[Bigjohn1]

Re: Shift clunk and Flo-Torque hubs

Walley - good info, thanks. Sounds like I need to retrofit with a Flo-Torque III and double the torque value to 100lbft. We'll see what this does....

 

[walleyehed]

Re: Shift clunk and Flo-Torque hubs

Each hub kit comes with a piece of paper stating the torque value for each kit.

 

[DHPMARINE]

Re: Shift clunk and Flo-Torque hubs

I don't understand how different hubs or torques can cause a clunk,but maybe you can enlighten me.Of course if the prop nut is VERY loose .... the prop will move back and forth on the propshaft ..... I don't think that's what you mean.

That Trophy Plus 4 Blade.Is it a 4 stroke prop ?

Most Merc 4 strokes clunk when using the wrong prop.

DHP

 

[walleyehed]

Re: Shift clunk and Flo-Torque hubs

DHP, you're right...
The problem with the flo-torq hubs and XHS hubs is the fact very few read the instructions.
There are hubs specific to a given prop if run on a given (2 vs 4-stroke engine), the torque value is VERY important due to the fact the thrust washer and outer washer must squeeze down on the delrin sleeve or "excess" chatter takes place. The flo-torq III was developed for the 4-strokes up to 115 and the smaller Bigfoots. Torque is very important on the delrin sleeve hubs, not a big factor on std hubs.

 

[Bigjohn1]

Re: Shift clunk and Flo-Torque hubs

The jury is in from Merc Propeller Division and Walleyhed is 100% correct. They say to retrofit with Flo-Torque III which was designed for this problem. When I bought the prop last year, it came with the Flo-Torque II so that's what I installed it with...lesson learned.

 

[Bigjohn1]

Re: Shift clunk and Flo-Torque hubs

That Trophy Plus 4 Blade.Is it a 4 stroke prop ? Most Merc 4 strokes clunk when using the wrong prop.

DHP

For the benefit of the group, enlighten me on the difference between a 4-stroke and 2-stroke prop:^ For the record, a 20" Laser II and 18" Vengeance acted the exact same way on the engine (clunked). Only the stock aluminum Black Max did not clunk. Merc recommends any of these props (dependent on boat loading) with my particular boat/engine combination and even supplied the 18 Vengeance from the factory.

 

[walleyehed]

Re: Shift clunk and Flo-Torque hubs

I've spent several phone calls with Mercury deciding if this was an issue or not...according to Merc, this is normal for the flo-torq systems and is no concern for wear, no warranty issues or other-wise.

 

[gss036]

Re: Shift clunk and Flo-Torque hubs

This is a discussion on the same subject over on the Whaler board. Seems everyone is trying to figure out the problem w/4 blade props.
http://continuouswave.com/ubb/Forum4/HTML/004930.html

 

[walleyehed]

Re: Shift clunk and Flo-Torque hubs

Interesting bunch over there...I wonder if any of them know there are props that will blow away the die-hard Merc versions they are listing...slap on a set of Fusion 4, or OS1 and OS 2 Turbos and see where that rev-4 stands.....8)

 

[Bigjohn1]

Re: Shift clunk and Flo-Torque hubs

My Flo-torque III hub is on the way. I'll read the supplied instructions closely and torque to the stated value. I'll report back here with results - fingers crossed.

walleyhed, just so we're straight on this, I realize this is not a factory defect and is normal when running a heavy ss prop on this engine. Still, if there's a way to minimize it, I'll give it a try.

 

[walleyehed]

Re: Shift clunk and Flo-Torque hubs

I finally caught one of the engineers in the prop division today and here is a copy of what I posted on the same subject in the prop forum.......

"OK, I got to talk with Roger at Merc prop division....
He says I am the first to question the rattle or clunk of the flo-torqII.......
He also told me all in-line 4 Verados and all 3-cylinder Mercs are now shipped with a flo-torq III & IV hub kits installed on the prop shaft because they rattle...
I'm told the paper listing 100ftlbs is for liability only and you will "feel" when the Delrin sleeve "seats", but it should be atleast 55ftlbs, but may take more.
The Flo-torq IV has the long splines and must be reamed-out 3/4"(splines removed), just like any merc or yammy prop to fit JohnRudes.
His answer to the Rattle was "not to idle so much", and if you do, the flo-torq system "may not be for you".
The flo-torq IV is good to 200hp.
Thank you, have a nice day................... "

 

[Texasmark]

Re: Shift clunk and Flo-Torque hubs

Hey Ken,

Made it by the local Merc dealer the other day. He showed me a Flo-Torque hub and we discussed the details.....no new info from what has been discussed here. Did see where you have to mash the delrin onto the hub. He said his sweet spot has been 90 ft-lbs.

He got a set of gears and a clutch dog out and we went through the operation of the clutch dog in the "rattle" senario also. No new info there either and it seems that everyone understands what's going on there.

Later,

Mark