Woe's since installing S/S prop

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Also forgot to mention...

The original alum prop had a Flo-Torq hub installed like this one: http://url.ie/1uc

The stainless steel one has the type of hub where there is a plastic ring around the perimeter of the hub. This actually kind of worried me because I had to use a spacer on the side with the nut, and I have nowhere to press down the wings on the washer to stop the nut from, but I was assured once the locknut is nice and tight there won't be a problem. The prop is nice and tight. Here is the prop: http://cgi.ebay.com/ebaymotors/ws/e...70011765706&rd=1&sspagename=STRK:MEWN:IT&rd=1

 

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Woe's since installing S/S prop

Hi everyone, I am re-posting this here as I feel this is the best place for it. Here it goes...

I have a Mercruiser 1.7 (120HP) Turbo-Diesel on my sports cuddy with an Alpha 1 Gen II leg

It came as standard with a 14 x 23 aluminium prop, but was over-revving, so I upgraded to a 14.25 x 24 stainless steel prop. I fitted it up nice and tight. Nothing is loose, there is no play on the spline. The prop rotates freely and doesnt come in contact with any part of the leg

When I put the engine into gear, there is a very loud 'thumping' noise until I hit 1200RPM. Once I hit this RPM it stops. This did not happen with the aluminium prop. I am worried that I might be doing damage to my gearbox. Has anyone had anything similar happen to them? The noise is definately coming from the leg, because the noise goes when I put the engine into neutral. Could it be the extra load thats making the noise?

Any help much appreciated!

 

[Texasmark]

Re: Woe's since installing S/S prop

Let's try "clutch dog rattle". Same thing happened to me and it is very noticeable on my 24" pitched SS prop.

Annoying sound, but according to the local Merc mechanic, Merc put out a letter on it and it is not hurting anything. Said you get it with low rpm's on heavy SS props with lotta pitch. :'(

So, it's put up with the noise or go back to a lightweight alum prop.

Just to prove it, I bought an alum prop which stopped it, best I could tell, but the alum prop was a 23" pitch and I lost 600 rpm's running it. It's currently sitting on th shelf and I do a lot of shifting into and out of gear when manuevering onto the trailer.....Notice it only does it in F where the clutch dog can slip. Can't rattle in R because there is no clutch, it's hard locked in place.

HTH

Mark

 

[walleyehed]

Re: Woe's since installing S/S prop

Also, the Rampage, I believe, is a Michigan wheel prop...not Merc, and it "may not" be for a Merc.
It requires different washers because it has a different hub length.

 

[Texasmark]

Re: Woe's since installing S/S prop

Hey Kenny, while I have your attention,

Got any ideas about why I lost 600 rpm's. Was running the Ballistic 13 1/2 x 24 XP (bought off this site).

Got a Hustler 14 1/4 x 23 alum, also off this site. The Hustler was made for the 14 1/2 gearbox (V6 engine box) which made it's hub diameter the same as the diameter of the gearbox on my 90 hp I 3cyl (didn't know it at the time of purchase).

I built a spacer so that I could run it and it set the prop about 3/8 " back from where it would have been had it had a 14" dia. Just far enough back so that it would clear the lip on the gearbox (that the regular 4" prop would normally slide under). Doubt that the dia played a part in the loss and the diameter of the hub did not protrude outside the gearbox diameter.

The blade shape on the Hustler was more conventional, cup a lot more pronounced and blades were much thicker, being alum. It was ported (Ballistic not) It was said to have progressive pitch and high rake (as the Ballistic).

I'm thinking cup, blade area, and leading edge thickness got me......but I should have recovered some of that being I dropped 1" in pitch. So, in reality I lost 800-850 rpm's between the two props and it cut 6 mph off my top end.

Thanks for your input. 8)

Mark

 

[Texasmark]

Re: Woe's since installing S/S prop

Bumping it up.

 

[Crownie2]

Re: Woe's since installing S/S prop

I don't know, but I am wondering if the spacer had anything to do with it.

Bob

 

[Texasmark]

Re: Woe's since installing S/S prop

I made it so that the hub would just clear the housing; like 1/32" when you push it in. After the run, when I took it off, no paint was scraped off either at the housing hub interface, so I know it wasn't rubbing.

I didn't gain rpm's, I lost them, so I know it wasn't slipping.

For now it tells me that that the Ballistic is giving me better performance than I thought. I mean, when you roll 50+ mph (49 into the wind, 50+ with it) in July in a 17' boat with 90 hp something must be right.

Mark

 

[Crownie2]

Re: Woe's since installing S/S prop

The Ballistic is well thought of by many.

I am betting that if you have a Merc engine that a Merc prop with the Flo Torque II hub system would not rattle.

Bob

 

[Texasmark]

Re: Woe's since installing S/S prop

Hub's not rattling man. The clutch dog is.

The clutch dog slides back and forth on the prop shaft shuttling between F(thru N) to R gears. It's what actually does the shifting for you and is moved by the shifting fork connected to your gear shifter lever.

The F and R gears turn as long as the drive shaft is turning. They are permanently meshed and since one is in front and the other is in the rear of the driveshaft, they turn in opposite directions.

It's up to the clutch dog to engage the gear you want for the direction you want the prop shaft to travel.

On the front of it is a sawtooth gear pattern. On the rear of F gear is the inverse saw tooth pattern. On the rear of it are straight teeth (cogs) as are (inverse cogs) on the front of the R gear. R can't rattle cause when you get in R you stay there till you shift out of it.

You can feel all this by shifting (carefully) with the engine off and rotating the prop in both directions.....don't force it into R....turn the prop slowly as you shift till the gears line up, then it will drop right in.

In F it will lock trying to turn it ccw (looking from the rear) and click cw. In R it locks in both directions.

Anytime the prop is going faster than the engine the teeth skip over each other.....and make a rattling noise. This happens every time you decelerate; you just don't hear it. That's the reason for the arrangement.

I guarantee you that if it weren't for that when you shut down the throttle, the boat would do a nose dive. It'd be like throwing a giant sea anchor out at 40 mph. :% Bet it was funny the first time they (OMC probably) put a shifter on an OB. Bet they didn't think about needing a "slip clutch", which is what the dog is, besides a shifting shuttle.

When the engine is doing the driving, the perpindicular edges on F (and the front of the dog) butt joint and lock and you get drive power to your prop.

Apparently on engines with few cylinders (like mine, only 3) and high pitched (24 in my case), heavy props (a heavy SS sucker), there is enough turbulence at idle that the engine doesn't always drive the prop.

My last engine was an I6 and when I bought it it had a 24 on it which I had to exchange (too much prop). It didn't rattle; course, the tower ran like a sewing machine.

So the prop jumps back and forth from being driven (quiet) to trying to drive (rattle).

HTH

Mark

 

[walleyehed]

Re: Woe's since installing S/S prop

As Mark is saying, the clutch dog is rattling, not the hub...
Any time a flo-torq or XHS system is used with the delrin sleeve, the clutch rattle will be there at Idle. The Flo-torq III can be used insted up to 175HP and it has some rubber to it and will eliminate "dog rattle".
Mark, as to why the RPM drop, I can't answer that...The Ballistic is "typically" a hard pulling prop...usually drops RPM in comparison to a simular SS in the same pitch.
You're running the XL and that's the only 3-bld Ballistic to give any "real" performance. The Hustler is an aggresive alum prop, but an inch down should in no way, have put you where it did.
I've not experienced anything like that in the Hustlers I've ran when comparing pitch numbers to SS.

EDIT...the Blade area of the Hustler might have got you a bit on this one, Mark...Not the diameter per say, but shear bld area...

 

[Texasmark]

Re: Woe's since installing S/S prop

Thanks Ken. I have been wondering about this. No big deal, but being retired, and not having all the high tech business problems to worry about and all, all I worry about now is my boat and my cows. Geez, if you didn't have something to worry about, what would you do with your day.................go fishin ? 8)

Mark

 

[jrbachman]

Re: Woe's since installing S/S prop

I have an outboard 225 merc that has clutch dog rattle with a 15.5x15 ss 4 blade but no rattle with 14.5x17 3 blade ss.If your interested in getting rid of the rattle its possible but you would need a prop shop that does lending or it could get expenssive.Just a thought because I didnt like to hear the gear box making sounds like that when I cant see land. later Jason

 

[walleyehed]

Re: Woe's since installing S/S prop

Picking a prop because it is quiet is the last reason for prop choice. Some of the early Michigan SS wheels were VERY heavy and caused some noise, but that's not a concern according to the engine builders.
I'm going to a flo-torq III on the Enertias to see if it changes anything.

 

[Crownie2]

Re: Woe's since installing S/S prop

I thought the Flo-Torq II was the latest and greatest - is there a III now? What's the difference?

Bob

 

[walleyehed]

Re: Woe's since installing S/S prop

the III has actual rubber in it...designed originally in a larger form for Bravo drives...

 

[Texasmark]

Re: Woe's since installing S/S prop

Ok Ken, confused again. You are talking about rubber. My Ballistic has a rubber slip hub. I know that some of the props nowadays (Hustler for one) has a plastic hub with a brass insert.

Now, are you talking about more rubber, or rubber in a different location as compared to the rubber slip hubs that have been around for years and years? Or are you referring to the regular slip hubs which on my engine are causing dog rattle.

Thanks,

Mark

 

[walleyehed]

Re: Woe's since installing S/S prop

2 types of hubs...built-in rubber and replaceable by-consumer sleeve-type hubs(flo-torq 1, 2, 3, and XHS hub systems) all of the consumer changeable hubs use delrin type, hard plastic insted of rubber. Now there is a replaceable sleeve with rubber insted of delrin (plastic-no give.)

 

[Texasmark]

Re: Woe's since installing S/S prop

Okaye, Thanks for the info Ken. Agree on the plastic no give also. Upon inspecting my Hustler's plastic (and brass) hub, it's obvious that it's a non slip hub. If you whack something really good, delrin and brass are going to be flying 6 ways to Ssunday and you'll have to walk back to the dock. :% .

Mark

 

[Crownie2]

Re: Woe's since installing S/S prop

According to Merc, and from what I can see of the design of the Flo-Torq II, the hub is designed to "flex" a little to smooth out things like "shift-shock" and will "break away" when contact is made with something solid. And of course, the best part is that should you hit something :devil: it is easily replaceable!

Bob