# correct prop pitch



## JakeBrake (Jan 28, 2009)

I'm sure this isn't the correct forum for this question but here goes. I have a 75hp mecury that was on a bass boat & now mounted to my 24' pontoon boat. It won't go!! It has a 17 pitch on it and I think it needs to be much less. But the boat shop guy argues the 17 is right. It just doesn't make sense to me. I see prop pitch like the gear ratios of the 18 wheelers that I sell. It needs a smaller pitch! (Or in my occupation a lower gear ratio) Thoughts????


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## Lonestar Proud (Oct 26, 2010)

What do you mean "it won't go"? A 75 hp on a 24' pontoon isn't going to go very fast because that's a lot of aluminum plowing through the water.
The smaller the pitch, the less speed but more rpm's you are going to turn. Higher pitch, lower rpm's, more speed, but too much pitch and you'll lose all your low end "get outta the hole" power.
I don't know what the max rpm's is for a 75 merc, but you don't want to revving it at max rpm all the time.

-LP


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## FISHROADIE (Apr 2, 2010)

That is a small motor for a big boat, but I found this maybe it will help, props are expencive these days.

http://www.tropicalboating.com/powerboating/choosing-a-propeller.html


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## JakeBrake (Jan 28, 2009)

I mean idle is all I can get. If you throttle up on it, it only lugs up. Unless you raise the motor up enough to get some cavitation, then you can get rpms up. Its only rated for a 90hp anyway. I looked upp someother websites with pitch calcs and a 13-15 is recommended with my combination ....


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## shadslinger (Aug 21, 2005)

Prop pitch is everything on big boats, mine is very specific and I wasted a lot of $ getting the right prop after the first aluminum one bit the dust. The wrong ones would do just like you described.
When I got it right I bought a SS one and it has been great.
Check with a lot of people who know boats well before you spend any more $ so you can get it right.


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## FISHROADIE (Apr 2, 2010)

JakeBrake said:


> I mean idle is all I can get. If you throttle up on it, it only lugs up. Unless you raise the motor up enough to get some cavitation, then you can get rpms up. Its only rated for a 90hp anyway. I looked upp someother websites with pitch calcs and a 13-15 is recommended with my combination ....


They make 4 and 5 bladed props too, they will get your boat moving faster and you loose some top end, but not that much. With the price of props these days you dont want to have to keep buying them till you find the right one. I would call or go buy and talk to the guys at lake side boat repair on 105, the older guy there knows his props. He refused to sell me a knew prop when I bent mine, he said they cost to much, he took a torch and a block of wood and a brass hammer and straightend mine right out. I have had no vibrations, and he charged me 15 bucks.


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## JakeBrake (Jan 28, 2009)

Well I just talked with blaise at vz and he agrees I need a 13 pitch. Anyone have a prop they want to trade for a s/s 17


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## rubberducky (Mar 19, 2010)

Is the rpms going way hight when you tell it to go. Maybe you have a bad hub? When the hub goes out it will idel but when you give it any more just spins the hub. I'm not sure if this is what it is or not I'm riding around on a little boat so not much help.
James


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## JakeBrake (Jan 28, 2009)

rubberducky said:


> Is the rpms going way hight when you tell it to go. Maybe you have a bad hub? When the hub goes out it will idel but when you give it any more just spins the hub. I'm not sure if this is what it is or not I'm riding around on a little boat so not much help.
> James


Hub is good. I am trying to push a barge with a windmill propeller powered by a weed eater motor..... I am pretty sure a smaller pitch is the remedy now.... I don't need a ton of speed and don't expect it with a 24footer and a 75hp. But I do expect a lot more than walking speed! Haha


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## scott2h2 (Dec 24, 2009)

I have a 50hp on a 21' pontoon with an 11 pitch. My wot should not and does not exceed 5500rpm. I seem to recall reading somewhere that wot on most mercs is around 5500. Keep that in mind when you are trying props. If you are in or near coldspring you are welcome to try my prop if it will swap. Pm me and let me know.


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## Mattsfishin (Aug 23, 2009)

I have a new aluminum prop for a 90 hp Mercury 2004. If it will fit you can try it but I don't want to sell it. I keep it for a spare in my boat just in case.

Matt


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## Jeff G (May 18, 2010)

scott2h2 said:


> I have a 50hp on a 21' pontoon with an 11 pitch. My wot should not and does not exceed 5500rpm. I seem to recall reading somewhere that wot on most mercs is around 5500. Keep that in mind when you are trying props. If you are in or near coldspring you are welcome to try my prop if it will swap. Pm me and let me know.


I would say you need alot lower number prop than a 17 . 11 would be my guess if I had to pick out of the blue . The offer to try a prop from Scott would be a great thing to do . If you have a tach and know your optimal running recommended than you should be able to dual it in close . One pitch off or two makes a huge difference .


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## dbullard (Feb 13, 2008)

My 20 ft has 88 hp with a 13 pitch . It will top out at about 22 mph on the gps.


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## Whitebassfisher (May 4, 2007)

I think that you are right to the extent that prop pitch is much like the gear ratio on a truck. And yes less pitch would be like changing a car from a 3.73 to a 4.11 or whatever. You obviously understand that, but I see props as much more complicated because props always have a certain amount of slippage, where as tires are not always breaking loose or peeling out. In addition to pitch and diameter there is cupping and rake. Props are extremely important and expensive so you need a pro's guidance. The slippage will be greatest at take off of course, and I think it is possible that after you are at full speed and crusing that slippage may be as low as 5% or even slightly less.


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## lx22f/c (Jun 19, 2009)

One thing to remember is pontoons don't plane they plow. When i got mine i was shocked on how thet drove, mine came with a 13 pitch and after breaking it in we found we were turning too many rpm's. mine is a 22ft with a 115 4 stoke yamaha. My dealer said i should load the boat with the load it normally will have and ck rpm's i did and with 8 people and coolers i would still bust 6000 rpm's. we put a 15 one and with same load we now turned 5900 which is right on, so i think a 13 or a 15 might work. another thing you may try raising the motor a notch and see if that helps.


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## JakeBrake (Jan 28, 2009)

scott2h2 said:


> I have a 50hp on a 21' pontoon with an 11 pitch. My wot should not and does not exceed 5500rpm. I seem to recall reading somewhere that wot on most mercs is around 5500. Keep that in mind when you are trying props. If you are in or near coldspring you are welcome to try my prop if it will swap. Pm me and let me know.


Dude, I live in coldspring.... LOL! Thanks for the offer bro, but I am going to swap the 17 that came with the boat with the guy I bought it from til we get the right one on it..... thank you all for your input...


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## Git$um (Feb 11, 2008)

I have a 20 foot pontoonm with a 60hp Evinrude. the prop pitch is 15 and works well.


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## ronniewelsh (Feb 3, 2011)

well I dont claim to know everything about anything but I can speak from experience and its been my experience that the smaller the pitch the faster you can achieve higher rpms but when you get to the higher rpms you give up high end speed.With a bigger pitch it may take a little longer to get your max rpms but the boat will go faster.If your boat is not eventually plaining out then you have other issues such as trim/tilt,hp vs weight etc......Good Luck!!!!!!!!


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## ronniewelsh (Feb 3, 2011)

ronniewelsh said:


> well I dont claim to know everything about anything but I can speak from experience and its been my experience that the smaller the pitch the faster you can achieve higher rpms but when you get to the higher rpms you give up high end speed.With a bigger pitch it may take a little longer to get your max rpms but the boat will go faster.If your boat is not eventually plaining out then you have other issues such as trim/tilt,hp vs weight etc......Good Luck!!!!!!!!


 I should also add that Im assuming you know for a fact that you dont have some power head issue(like a dead hole or fuel mixture problems or something like that)because that kind of stuff will drive you bananas!!


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## JakeBrake (Jan 28, 2009)

ronniewelsh said:


> I should also add that Im assuming you know for a fact that you dont have some power head issue(like a dead hole or fuel mixture problems or something like that)because that kind of stuff will drive you bananas!!


Compression and all that is good..... I am 99.9% sure its prop pitch issue. Talked to Louie baumann and before I could finish the scenario he blurted out pitch problem and said to get a 13:


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## ronniewelsh (Feb 3, 2011)

JakeBrake said:


> Compression and all that is good..... I am 99.9% sure its prop pitch issue. Talked to Louie baumann and before I could finish the scenario he blurted out pitch problem and said to get a 13:


 Cool! I hope you get her goin! hey is that bauman down in the east end of houston?


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## Swampus (Sep 1, 2005)

How do you know the pitch? I dunno.................

My Brother has a pontoon also--think a 21-24ft --how low do you think the motor/prop needs to be in the water? Has the "fins" in front for getting on plane better--still slow with the 50hp....he wants a 115hp to go a bit faster. Some say it won't make a bunch of diff. because it is still plowing thru the water.........again Dunno--only had V Hull Boats myself.


swamp....................in the dark on pitch.


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## ronniewelsh (Feb 3, 2011)

Swampus said:


> How do you know the pitch? I dunno.................
> 
> My Brother has a pontoon also--think a 21-24ft --how low do you think the motor/prop needs to be in the water? Has the "fins" in front for getting on plane better--still slow with the 50hp....he wants a 115hp to go a bit faster. Some say it won't make a bunch of diff. because it is still plowing thru the water.........again Dunno--only had V Hull Boats myself.
> 
> swamp....................in the dark on pitch.


 It should be stamped on the hub


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## Git$um (Feb 11, 2008)

The larger motor will make a difference, but not like a speed boat.


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## JakeBrake (Jan 28, 2009)

You would have to have a pretty big motor to get a **** on plane.... my 24ft is only rated for a 90hp. I think that's due mostly to transum. I don't want it to be a speed boat, just faster than walking speed


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## JakeBrake (Jan 28, 2009)

Update:
the 13" pitch was exactly what it needed!!! Took it to trinity [email protected] hwy19 and the family and I had a blast!!!


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## shadslinger (Aug 21, 2005)

Glad you found the right pitch, nothing but fun ahead now!


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## wwind3 (Sep 30, 2009)

JakeBrake said:


> Update:
> the 13" pitch was exactly what it needed!!! Took it to trinity [email protected] hwy19 and the family and I had a blast!!!


Congrats--I have the opposite prob--overrevving.

I have a 20 ft lowe with 90 Merc Optimax, 25 in logs and underskinning. My boat leaps out of the hole and runs 27 WOT which is 5800 rpm. I think the big logs and underskinning helps it plane out a little better.

I am thinking about adding a little cup or one more inch of pitch up to 17. I dont like hitting my rev limiter.

Would cupping or adding pitch be a better idea? Thanx..

PS-when new I could do 29--even hit 30 once in the winter--but now 27 is it. Logs are clean-boat stays in a hoist. Any ideas?


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## FISHROADIE (Apr 2, 2010)

JakeBrake said:


> Update:
> the 13" pitch was exactly what it needed!!! Took it to trinity [email protected] hwy19 and the family and I had a blast!!!


Glad you got it sorted, don't drive that thing to fast now.


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## Lonestar Proud (Oct 26, 2010)

Good deal Jake, glad you got it running the way you want it.


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## JakeBrake (Jan 28, 2009)

Fast it won't go!!! I don't see a 24.5' pontoon being a speed boat with a 75hp on it, but it will go and according to my GPS it runs around 20mph.. fast enough for me anyway... I need to get my tach fixed so I can make sure I'm running the proper rpms. Louie said that my engine should run at around 5200rpm.

wwind3: according to the research I did before buying my prop, 1" of pitch will affect the rpm by 200rpms.... 1" more = 200rpm less! 
Loui Baumann would be "THE" guy to call and ask... 713-926-6908 Baumann Props in Houston... He could answer your question on cupping or pitch change..


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## wwind3 (Sep 30, 2009)

JakeBrake said:


> Fast it won't go!!! I don't see a 24.5' pontoon being a speed boat with a 75hp on it, but it will go and according to my GPS it runs around 20mph.. fast enough for me anyway... I need to get my tach fixed so I can make sure I'm running the proper rpms. Louie said that my engine should run at around 5200rpm.
> 
> wwind3: according to the research I did before buying my prop, 1" of pitch will affect the rpm by 200rpms.... 1" more = 200rpm less!
> Loui Baumann would be "THE" guy to call and ask... 713-926-6908 Baumann Props in Houston... He could answer your question on cupping or pitch change..


10-4 on Louie--he did some work on my last bass boat and it ran great.


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## redfisher43 (Oct 7, 2005)

I have q 22' pontoon w/90 hp Mercury. Has a 13 3/4 x 13 aluminum 3 blade and turns 5400 WOT. Top end about 16.


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## jblrail (Mar 31, 2005)

*prop doc*

Cannot say enough good about Louie Baumann. Take him your prop and he will take time to really listen to you and then give you the best options. He has fixed problems on two different boats and been very reasonable on price. I trust him.


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