prop stress on 200 coned carrier?

[hirk]

I have the stock carrier and read on s&f that a 3 blade prop put alot more stress on it than 4's and will wallow it out.My question is will the case live longer running a 4 blade vs 3 or does it really make a difference? I will be running 13" setback even with the pad on a 2003 with a 150 or 225pm 6800max.

 

[whipper]

Pitch has more of an effect on stress than the number of blades. The number of blades has more of an effect on the durability of the prop more than the internals I feel. A 3 blade prop has 33% load per blade were as a 4 blade has 20%. A 4 blade has a better ability to stay hooked up in turns and surfacing. But a 3 blade is usually but not always lighter than a 4 blade. So I would put more emphasis on the intended use and pitch over saying in general a 3 blade or 4 blade is better or worse on the gearcases internals. For me I would rather run a 26 3 blade to 7400 than a 30 pitch 4 blade to 6800. i would believe the 26 3 blade is being easier on the gearcase than the 30 pitch 4. taking into consideration our surfacing ability with allisons a higher rake prop of any blade will help reduce slippage. So as long as the pitch can match the runnability of the load into the max rpm range of the motor i cant see there being a problem with either. There is a pressure reduction with 4 blades because more blades aerate the surface of the water more than 3. But since there are more blades coming around in a closer rotational distance there is also better bite. So in this case there would be less stress on the gearcase created with 4 blades then 3. Also to achieve the same top speeds you can pitch down with 4 blades due to lower slip percentages generally. But all this is prop style and performance dependant. These comparisons would have more of an ill effect with a 260 turning 8000 rpm+ more so than a 225 turning 6800 with the same 200 case. Stay away from 29 and 30 pitch props and your 200 case will be just fine I think. I would up your limiter and turn 3 or 4 blades in the 26 or less pitch range to get the best longevity out of your gearcase over turning 28+ to 6800. Sorry for the long explanation but I felt it was to blanket of a term with many variables. Theres even a lot more to it than just this.:big grin
Bottom line, limit the use of taller pitch props, so up your limiter is your best bet for long life. Just mix your oil well and use good fuel ,aces,smaller props and let er rip!:big grin

 

[silverbullet02]

Pitch has more of an effect on stress than the number of blades. The number of blades has more of an effect on the durability of the prop more than the internals I feel. A 3 blade prop has 33% load per blade were as a 4 blade has 20%.

Doesn't each blade on a 3 blade have close to 100% of the load on each blade due to only about one being in the water (roughly)?

A 4 blade has a better ability to stay hooked up in turns and surfacing. But a 3 blade is usually but not always lighter than a 4 blade. So I would put more emphasis on the intended use and pitch over saying in general a 3 blade or 4 blade is better or worse on the gearcases internals. For me I would rather run a 26 3 blade to 7400 than a 30 pitch 4 blade to 6800. i would believe the 26 3 blade is being easier on the gearcase than the 30 pitch 4.

I'm not following you on this. How does pitch affect stress on the carrier?

taking into consideration our surfacing ability with allisons a higher rake prop of any blade will help reduce slippage. So as long as the pitch can match the runnability of the load into the max rpm range of the motor i cant see there being a problem with either. There is a pressure reduction with 4 blades because more blades aerate the surface of the water more than 3.

What pressure reduction?

But since there are more blades coming around in a closer rotational distance there is also better bite. So in this case there would be less stress on the gearcase created with 4 blades then 3. Also to achieve the same top speeds you can pitch down with 4 blades due to lower slip percentages generally. But all this is prop style and performance dependant. These comparisons would have more of an ill effect with a 260 turning 8000 rpm+ more so than a 225 turning 6800 with the same 200 case. Stay away from 29 and 30 pitch props and your 200 case will be just fine I think. I would up your limiter and turn 3 or 4 blades in the 26 or less pitch range to get the best longevity out of your gearcase over turning 28+ to 6800. Sorry for the long explanation but I felt it was to blanket of a term with many variables. Theres even a lot more to it than just this.:big grin
Bottom line, limit the use of taller pitch props, so up your limiter is your best bet for long life. Just mix your oil well and use good fuel ,aces,smaller props and let er rip!:big grin

I'm not picking, just a lot to read at 630am and trying to understand. :beer:

 

[GotMyAlly]

I agree with silverbullet. With a surfacing prop, a 3 blade would only have one blade in the water at many points in the rotation. That would mean one blade carrying all of the load. A 4 blade would have 2 blades in the water through most of the rotation. BUT....I would think that would have more impact on the life of the prop than the gearcase.

My experience is that 3 blades typically have more bow lift. The prop imparts that leverage directly on the propshaft.

The other factor is steering torque. That's got to be rough on the case too. Sometimes that can be mitigated with motor height. Some props just have more steering torque than others. A lot of time, like whipper said, it's the higher pitched props that demonstrate more steering torque. If it's pulling so hard that you can barely hold the wheel straight......I'd look for another prop.

 

[hirk]

This gist of what I had read on s&f suggested that with 1 blade in the water vs the 2 blades of a 4 blade that the 3 blade put considerably more load or stress on the carrier, it sounds good but is it fact???? I like running choppers and have a 24 & 28 and have ran a 4 in the past but to me its like comparing driving a caddy vs a viper, I prefer the viper but if it can save a case rebuild I may have to drive the caddy.I won't be running really high either as my cone is a bobs combo with 3 holes under and 2 above (unless I could block the top 2 and still have good flow). I have only ran it twice and didnt measure the height since I wasnt touching the setup till I replaced the pooched water pressure gauge but it ran 75 with a 26 chopper and the 150 so it must not be too far below pad.

 

[whipper]

A good prop is a well balanced prop that would have very little steering torque weather its a 3 or 4 blade. Because 4 blades only have 20% of the load compared to 33% of a 3 blade you can get away with thinner blades on a 4 blade.
Like Neal said less rotational force on the blades of the 4 blade over 3 would make the 4 blade last longer. Providing it wasn't thinned to much.

i would also believe by plugging the top holes and running a more surfaced application would increase the life of the case. only because the speeds Allisons run. An Ideal prop shaft hight is half in half out running props designed for this application more {buried} with a prop thats skew and rake are designed to be aerated under the water more would have more stress on the carrier than with the prop free,ed up on top. With the prop shaft 2 or 3 inches below you now have two blades even from a 3 blade in the water with 33% load instead of two that have 20% if that makes sense. {just read this later in the day} :big grin

The biggest things thats the hardest on gear cases is not changing the gearlube often enough,To high of pitch for the power to weight ratio and takeoffs.

 

[GotMyAlly]

The biggest things thats the hardest on gear cases is not changing the gearlube often enough,To high of pitch for the power to weight ratio and takeoffs.

Yep, poppin' wheelies probably ain't good for 'em! LOL

 

[TBuck2003]

Motor height and surfacing prop are the hardest thing on the lower unit. The up and down motion it puts on the prop shaft is the killer. The 3 vs. 4 blade is moot to the gear case. Height is what kills a stock case...

 

[whipper]

Motor height and surfacing prop are the hardest thing on the lower unit. The up and down motion it puts on the prop shaft is the killer. The 3 vs. 4 blade is moot to the gear case. Height is what kills a stock case...

Yes but on an fast boat like an Allison would running 75-80mph submerged be less stress on the prop shaft than tuning the same prop even on flat water? I understand the surfaced and up and down motion.

 

[Bobalouie]

I would think yes, because a prop fully submerged has equal loading at all times on the blades, which would thrust load the propshaft along its axis. The propshaft doesnt care if it is loaded on its axis, thats the loading that it likes. If the prop is run surfaced, then you have uneven loading across the shaft which will impart a moment perpendicular to the axis that is constantly changing each time a blade comes out of the water. That will eventually lead to bearing or propshaft failure.

You are basically bending the propshaft back and forth like you would do a paperclip when you are trying to break it. Its the loading and unloading cycles of blades coming in and out of the water that imparts the moment, not the relative calm of the water, although that wold have an effect too.

 

[suicidealli]

Motor height and surfacing prop are the hardest thing on the lower unit. The up and down motion it puts on the prop shaft is the killer. The 3 vs. 4 blade is moot to the gear case. Height is what kills a stock case...

I agree with Todd. Surfacing a case is the hardest on them. If you run in choppy water the prop will be out of the water as mush as in the water. Eats stock cases, and hard on any case.

Roy

 

[GotMyAlly]

Got a hydraulic plate? Bury the prop when you are just cruising around.

 

[catfish123]

I agree.......I've never found the boat to be hard to drive with the prop 1"-2" lower than the high spot for top end. I know many will probably disagree with that, but just posting my experiences with it.

 

[hirk]

Catfish I could feel the case not handle as well on my sporty when I dropped it down with hydro steering but this 200 coned had zero torque and was smooth as butter running the 24 chopper at 6300r's with the 150 and it doesn't have a tamer and is cable steer so im guessing it may have been up to 1" maybe a bit more under pad since I would expect wheel torque up higher,the case is in the basement so I won't know till the deep freeze is over were its at.

 

[whipper]

The 200 case is arguably one of the fastest cases to have on an Allison. They were designed for 150-200 hp motors and wont last long mated with a 225,260+ motor. There used to be kits available to beef up the internals for these great cases. Since you have one and there getting harder to find. I would spend the money and time to have the internals beefed up.They are a good inch smaller in diameter at the bullet so less drag than other 2.5 cases. Merc racing actually used to offer a kit with beefier drive shafts, prop shafts and bearing carriers for your case. Not sure if you can still buy those complete or not.

Theres a guy on S&F thats machining nice Billet 2.5 carriers. He could make you a nice sturdy one for your case no doubt buy the look of his talents.:beer:

So from what Todd and others have said on hear the up down motion of the blades when surfaced or the load created when submerged or in and out from just running theres always some type of load and stress thats going to take its toll one way or or another. Put it this way. Even the 2.5 small shaft has proven not up to some uses standards and guys went to the 2.5 fat shaft for fear of failure.

The original threads topic of 3 vs 4 blade. High skewed props enter the water with less force than a prop with less skew. The up down motion of that paper clip description would be less force on the prop shaft when the prop re-enters the water. Better for the prop also. I would have to think 4 blades with skew and thinned a little for weight would have even less up down due to the closeness of the blades over 3 blades? Yes the up down would have an extra up down but not as dramatic as with the time difference with less blades. Almost ALL super high HP boats the run toward the 200mph mark run 5 blades or more. Because there better balanced and more efficient. And probably because easier on the shafts. Todd would know all the reasons as he sells those type of props to those dudes with deep pockets and 200 mph boats.:beer:

Beef up that 200,s internals and you wont have to worry about all this stuff so much.:wink

PS, I Love these type of Topics ,good one hirk!! We all learn so much when putting our heads together. All this applies to all cases not just the XR/200 cases but any case.

 

[hirk]

Well I was debating whether to run it with a 225 but I dont trust the carrier to hold up long term and at about $500 installed to go to a good carrier I think I will save the case and use it on my 150 when im north of 60 and 75mph is ok.its a 1990's big bearing case hardly used,it was coned then sat on a bench as a spare for 10yrs so its like new, it can sit another 5 or 6. I'll run a sporty or cle with the 225.I was hoping a 4 blade would be easier on the carrier but it doesnt sound like it unless I keep the case burried which i dont mind with the 150 but that wont fly with the 225 for me.

 

[silverbullet02]

I'd just run it and have fun with either motor. That's just me though. Had a coned preload case on my xtb/ 150pm, ran low 80s. That was 5 years ago and it's still going strong today with a lot of miles on it.

 

[TBuck2003]

The 200 case is arguably one of the fastest cases to have on an Allison. They were designed for 150-200 hp motors and wont last long mated with a 225,260+ motor. There used to be kits available to beef up the internals for these great cases. Since you have one and there getting harder to find. I would spend the money and time to have the internals beefed up.They are a good inch smaller in diameter at the bullet so less drag than other 2.5 cases. Merc racing actually used to offer a kit with beefier drive shafts, prop shafts and bearing carriers for your case. Not sure if you can still buy those complete or not.

Theres a guy on S&F thats machining nice Billet 2.5 carriers. He could make you a nice sturdy one for your case no doubt buy the look of his talents.:beer:

So from what Todd and others have said on hear the up down motion of the blades when surfaced or the load created when submerged or in and out from just running theres always some type of load and stress thats going to take its toll one way or or another. Put it this way. Even the 2.5 small shaft has proven not up to some uses standards and guys went to the 2.5 fat shaft for fear of failure.

The original threads topic of 3 vs 4 blade. High skewed props enter the water with less force than a prop with less skew. The up down motion of that paper clip description would be less force on the prop shaft when the prop re-enters the water. Better for the prop also. I would have to think 4 blades with skew and thinned a little for weight would have even less up down due to the closeness of the blades over 3 blades? Yes the up down would have an extra up down but not as dramatic as with the time difference with less blades. Almost ALL super high HP boats the run toward the 200mph mark run 5 blades or more. Because there better balanced and more efficient. And probably because easier on the shafts. Todd would know all the reasons as he sells those type of props to those dudes with deep pockets and 200 mph boats.:beer:

Beef up that 200,s internals and you wont have to worry about all this stuff so much.:wink

PS, I Love these type of Topics ,good one hirk!! We all learn so much when putting our heads together. All this applies to all cases not just the XR/200 cases but any case.

Whipper the 200 plus MPH boats run 5 or 6 blades due to efficiency because of drive height. These are all surfacing drives and props. The extreme heights needed for speed is why they have to run the 5 and 6 blade props. Remember the less blades you have the less horsepower you use to turn it. But with that being said you would never get on plane or push such an animal with a two blade... So you have to run a said prop which will give you the most efficient PUSH !!!! These applications are a KILLER on the shafts but that is why they are running some high dollar SH*T like the #6 Speedmasters on those applications !!!

 

[Hotprop]

How about just putting a heavy duty carrier in the gear case and it will last a long time..

 

[whipper]

Whipper the 200 plus MPH boats run 5 or 6 blades due to efficiency because of drive height. These are all surfacing drives and props. The extreme heights needed for speed is why they have to run the 5 and 6 blade props. Remember the less blades you have the less horsepower you use to turn it. But with that being said you would never get on plane or push such an animal with a two blade... So you have to run a said prop which will give you the most efficient PUSH !!!! These applications are a KILLER on the shafts but that is why they are running some high dollar SH*T like the #6 Speedmasters on those applications !!!

Great info thankyou for explaining that to me Todd.:beer: So basicly 4 blades need more power to turn hence the pitch down method for running 4 blades over three with outboards. You loose around 200 rpm going to a 4 blade over a three in the same pitch?

Todd what do you think about running a smaller 4 blade over running a taller 3 blade as far as carrier or shaft wear? Would it depend on the regular hight your running the prop shaft at? What's easier on the prop shaft and carrier at even or above the pad regardless of gearcase type for an outboard, 3 or 4 blade you think?