# 18 waterman with 70 2 stroke



## nsbsurfer15 (Jun 2, 2014)

Looking for advice on a 3 blade prop. Anybody with a 70 2 stroke on their waterman please chime in ! I have a 4 blade and its not anywhere where it should be as far as speed goes.

I know it was addressed a couple threads below this one but that gentleman had a 60 4 stroke.

Thanks !


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## TC (Feb 15, 2011)

I have an 07 18 Waterman with a 70 Yami 2 stroke. I have a PowerTech RED3R13PYM90 and a RED3R14PYM90. They both get on plane real quick, the hole shot's just a bit better with the 13. I'm seeing approx 35 mph with the 14, that's with two big guys and a full load. The 13 is just a tad slower top end. I prefer the 14. 

There's a couple of guys on here that have posted a little better numbers.


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## reallyshallow (May 19, 2010)

> Looking for advice on a 3 blade prop. Anybody with a 70 2 stroke on their waterman please chime in ! I have a 4 blade and its not anywhere where it should be as far as speed goes.
> 
> I know it was addressed a couple threads below this one but that gentleman had a 60 4 stroke.
> 
> Thanks !


Do you have a jackplate?


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## nsbsurfer15 (Jun 2, 2014)

Yes, skiff has a jackplate. I have heard people achieve 38-39 with the right 3 blade.


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## MariettaMike (Jun 14, 2012)

> Yes, skiff has a jackplate. I have heard people achieve 38-39 with the right 3 blade.


Some folks will report top speeds shown on their GPS while they are running with the current which can easily be 3-4 mph depending on conditions. Conversely some will report they are running slow when unknowingly heading into a current.

I think you should try the PowerTech SCD3 in 15 pitch to see if you can replicate the 38-39 numbers, else drop down to the SCD3 14.

For what its worth Yamaha ran a 17 pitch on a Skeeter bass boat to reach 38.3 mph at 5975 RPM.

http://yamahaoutboards.com/sites/default/files/bulletins/bulletin_otb_2StrokePerf_HPMidPort_70hp_02-121-SKT-B.pdf


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## nsbsurfer15 (Jun 2, 2014)

My buddy had a 3 blade on his with what seemed like a ton of pitch. He can't remember the prop and he sold his skiff. He was about 38. I'll check into that SCB


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## MariettaMike (Jun 14, 2012)

> My buddy had a 3 blade on his with what seemed like a ton of pitch. He can't remember the prop and he sold his skiff. He was about 38. I'll check into that SCB


I have an old SCD3 17 you are welcome to try if you're in the Orlando area.


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## Reel_Lucky2 (Sep 19, 2012)

A waterman with a tunnel is going to be relatively slow no matter what prop. They just aren't built for speed. That is probably the last consideration in the design. Hole shot and staying hooked up what high on the jack are what you should be maximizing with that boat IMHO. A 3 blade from Jack Foremann at crossroad props is a great choice for what I mentioned.


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## nsbsurfer15 (Jun 2, 2014)

> A waterman with a tunnel is going to be relatively slow no matter what prop. They just aren't built for speed. That is probably the last consideration in the design. Hole shot and staying hooked up what high on the jack are what you should be maximizing with that boat IMHO. A 3 blade from Jack Foremann at crossroad props is a great choice for what I mentioned.


The skiff does not have a tunnel


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## reallyshallow (May 19, 2010)

I have the same set up. I'm currently running the SCD4 17 pitch. Speeds between 36-38mph, runs best jacked all the way up and turns 56-58rpms trimming out and jacked up with no cavitation. If you have any other questions give me a shout. 7864234560 Ramiro. 

I'm in the process of ordering an SCD3 18 or 19 pitch and see if my top speed increases.


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## nsbsurfer15 (Jun 2, 2014)

> > My buddy had a 3 blade on his with what seemed like a ton of pitch. He can't remember the prop and he sold his skiff. He was about 38. I'll check into that SCB
> 
> 
> I have an old SCD3 17 you are welcome to try if you're in the Orlando area.


I will take you up on that for sure !


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## nsbsurfer15 (Jun 2, 2014)

> I have the same set up. I'm currently running the SCD4 17 pitch. Speeds between 36-38mph, runs best jacked all the way up and turns 56-58rpms trimming out and jacked up with no cavitation. If you have any other questions give me a shout. 7864234560 Ramiro.
> 
> I'm in the process of ordering an SCD3 18 or 19 pitch and see if my top speed increases.


Let me know what your numbers are with the 3 blade ! that would be great


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## MariettaMike (Jun 14, 2012)

> > > My buddy had a 3 blade on his with what seemed like a ton of pitch. He can't remember the prop and he sold his skiff. He was about 38. I'll check into that SCB
> >
> >
> > I have an old SCD3 17 you are welcome to try if you're in the Orlando area.
> ...


You've got it. I also have a SCD4R16P you can try when "we" go fly fishing in your Waterman.


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## nsbsurfer15 (Jun 2, 2014)

Well, I tested out Mike's prop. It increased my speed from 33 to 37-38 mph. However, the RPMs were 5900-6000 at WOT, which is too high. If anybody else has any suggestions I am open to them.

ReallyShallow, you get that 3 blade yet ??


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## MariettaMike (Jun 14, 2012)

Theoretically you should have been running 40.7644 to 41.4533 mph at those rpm's. But that old 17" prop was slipping around 4-5%. If you go with an 18 the best you can get with no slip is 40.2361 at 5500. If it slips 4% you're back to 38.6266 at 5500.

I also recall hearing a rule of thumb that rpm's will inversely change around 300 per inch of pitch. Go up to a 19 and WOT rpm's should drop to 5300-5400. 18 would be 5600-5700.

Personally I think you would be better off going with a 4 blade SCD 17 to reduce slip across the board and have a solid 38-39 mph top end without having to raise the jack plate so much. The 4 blade SCD lifts the stern more than the 3 blade. (At least it does for my boat.)


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## reallyshallow (May 19, 2010)

> Well, I tested out Mike's prop. It increased my speed from 33 to 37-38 mph. However, the RPMs were 5900-6000 at WOT, which is too high. If anybody else has any suggestions I am open to them.
> 
> ReallyShallow, you get that 3 blade yet ??



I have not yet, I will tell you that with my SCD4 17 pitch I see speeds between 36-38 mph at 56-5800 rpms, trimmed out.  Those rpms are with the jackplate all the way up, and you can literally trimmed it out as much as you want without cavitation, the SCD4 has awesome grip.


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## nsbsurfer15 (Jun 2, 2014)

Well, I bought the SCD4 17 pitch and it has excellent grip and can be elevated all the way up on the jackplate w/o blowing out. However, I am still not getting proper RPMs and only getting 35 mph top end. I can only achieve 5500-5600 with it trimmed way out and jacked all the way up and it is not really effective as far as gaining more speed. With the jackplate set all the way down or 4", I can only achieve 4,900-5,000 RPM. I am going to try and stay with this prop but go down a pitch or 2.


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## TC (Feb 15, 2011)

> Well, I bought the SCD4 17 pitch and it has excellent grip and can be elevated all the way up on the jackplate w/o blowing out. However, I am still not getting proper RPMs and only getting 35 mph top end. I can only achieve 5500-5600 with it trimmed way out and jacked all the way up and it is not really effective as far as gaining more speed. With the jackplate set all the way down or 4", I can only achieve 4,900-5,000 RPM. I am going to try and stay with this prop but go down a pitch or 2.


Keep us posted please. Very interested in your numbers. Thanks!


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## nsbsurfer15 (Jun 2, 2014)

I talked with powertech this morning and they recommended dropping down to a either a 14 or 15 pitch in the SCD... 14 sounds a little low to me so I might try the 15. this is already starting to get expensive !! lol


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## reallyshallow (May 19, 2010)

Seems like powertech props are not all the same, I'm getting 56-5800 rpms at 36-38mph with my SCD4 17". Why not consider the SCD3 17"?


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## nsbsurfer15 (Jun 2, 2014)

> Seems like powertech props are not all the same, I'm getting 56-5800 rpms at 36-38mph with my SCD4 17".  Why not consider the SCD3 17"?


I was able to get to that RPM range, but only if I had the jackplate all the way up and trimmed out. By doing that, I didn't gain anymore speed.. just got to the RPMs. Doing that is pretty much pointless, just uses more fuel without any speed benefit.


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## MariettaMike (Jun 14, 2012)

> I talked with powertech this morning and they recommended dropping down to a either a 14 or 15 pitch in the SCD... 14 sounds a little low to me so I might try the 15. this is already starting to get expensive !! lol


I've got a SCD4 16 we can try when we go fishing...hint..hint


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## nsbsurfer15 (Jun 2, 2014)

> > I talked with powertech this morning and they recommended dropping down to a either a 14 or 15 pitch in the SCD... 14 sounds a little low to me so I might try the 15. this is already starting to get expensive !! lol
> 
> 
> I've got a SCD4 16 we can try when we go fishing...hint..hint


You got my number ! Let's go. 

I got my 15 pitch in. Going to give it a try this weekend in the cold. I'll report back


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## nsbsurfer15 (Jun 2, 2014)

Tried out the 15 pitch. It is in the proper RPM range at about 55-56k with the best speed being 36. I am able to run the jackplate all the way up and the prop didn't blow out. However, the prop has a weird surging sensation at any elevation. It feels like it is very slightly slipping and catching but the RPMs do not change when this happens. Something is not right wth the prop. Might scrap the SCD all together and try a 3 blade


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## nsbsurfer15 (Jun 2, 2014)

A little update, I have finally been able to identify some props on other watermans. One is using the RED 3 blade 14 pitch with no jack plate and getting 39 mph at 5,800 RPM. Another is using the RED 3 blade in a 15 pitch and getting about 38 at 5,800. The second boat has a jack plate and cavitation plate. 

I called power tech and they recommended the 14 pitch over the 15 pitch just due to better speed. However, the question I presented was would the 15 pitch be better for holding at higher elevations on the jack plate over the 14 pitch ? They were not really sure but said in a perfect world the 15 would be better if i was able to rev it higher without it blowing out. Any thoughts ?? My head is starting to spin !!


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## Net 30 (Mar 24, 2012)

As long as you have a Ram-Lin trailer, the skiff should "function" properly no matter what prop you're running…... ;D


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## nsbsurfer15 (Jun 2, 2014)

> As long as you have a Ram-Lin trailer, the skiff should "function" properly no matter what prop you're running…... ;D


oh my.....


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## TailN (Dec 30, 2013)

^^^^^^  ;D  ;D


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## nsbsurfer15 (Jun 2, 2014)

***UPDATE***

I got the RED14 pitch in after power tech had a mix up and sent me the RED for the 50 hp motor. They took care of it very promptly and sent out a call tag for the wrong one they sent. Excellent customer service. 

Took it out today on the river and did some testing. Overall, I am happy with it but didn't quite hit the numbers I was expecting. The top speed that I saw was 37 mph at 5800, that was going with a slight current. I was able to run it up about 5" on the jackplate w/o it blowing out. The hole shot is better than my 4 blade as it gets up instantly with more torque. 

Another forum member has the same prop on his identical waterman w/o jack plate and he says he was seeing 39 mph. I'm beginning to think I might just have a slower hull ??? haha


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