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Author Topic:   2010 F70 speed results on a 15 Sport

JMARTIN posted 07-29-2011 02:12 PM ET (US)
This was not a real accurate, controlled test. I taped a Tom Tom to the dash and tried to read it and the tach and not run into anything.
1983 Sport 15, lots of layers of bottom paint, keel guard, 8 gallons of gas, and myself @ 140lbs. The boat probably has some extra water weight in it.
The heron did not stay around for the test.
http://i34.photobucket.com/albums/d137/jmartin-/DSCF9225.jpg

rpm mph
1000 4
2000 7
3000 16
3500 21
4000 25
5000 33
5500 36/37
6350 42
K 13 x 19 prop, one hole left to go up and I am sure it will handle one more hole up, but it holds so well now, I am going to leave it. The prop looks like aluminum to me. I have a picture of it somewhere.
John

JMARTIN posted 07-29-2011 02:19 PM ET (US)
Picture of the prop. The work order shows "use K 13 x 19 series prop" the invoice shows part # 6E5-45941-00-EL, description AL.PROP, 13x19
http://i34.photobucket.com/albums/d137/jmartin-/DSCF8072.jpg
John
tedious posted 07-30-2011 05:44 AM ET (US)
Thanks John! Your figures match the one reading I got at about 3700 RPM / 23 MPH / 10 MPG, before I was done in by the bad fuel connection.
I don't think my boat has extra weight in it, but given the sensitivity of the 15 to weight, the additional 100 pounds of weight in me will probably make a difference:-).
Tim
Tohsgib posted 07-31-2011 10:00 AM ET (US)
If invoice says K series I would check back with dealer as the K is a SS prop I believe. If so you cgot short changed.
Honestly I would work on props, 42 with a 70 is about 4-5mph short and a 60 can do that.
Peter posted 07-31-2011 10:46 AM ET (US)
That is a K series aluminum propeller. "K" does not mean stainless steel.
Keeper posted 07-31-2011 09:15 PM ET (US)
Thanks for the intel.
Good stuff !
Tohsgib posted 08-01-2011 10:45 AM ET (US)
My Bad...talk to Tom Clark and buy what he recommends.
Tom W Clark posted 08-01-2011 03:45 PM ET (US)
There are aluminum "K" series props and there are stainless steel "K" series props. The "K" simply refers to props made for intermediate gearcase motors.
The propeller John has is aluminum. There are better props out there.
JMARTIN posted 08-01-2011 04:30 PM ET (US)
If my goal was to go faster, I would raise to the last hole and get a stainless propeller. Since this boat pulls tubes, wake boards, skiers and is used in some rough conditions, I will stay with what I got until the prop gets dinged up, which it will. Sure, a stainless would be better, but this one is bought and paid for and it is a shared boat.
The hole shot is incredible and I have never lost grip with severe trimming and hard turns. On speed runs with lots of trim, you can hear the prop "howl" when you back down. It is really trimmed up, probably too far, which leads me to believe I can go up to the last hole with no detrimental effect on propeller grip. There is some uncomfortable chine walking sometimes at WOT. Trim and wind conditions help eliminate the walking.
John
Peter posted 08-01-2011 08:02 PM ET (US)
As a reference, my SuperSport 15 with a 2003 Yamaha 70 2-stroke (same 2.33:1 gear ratio as the F70) mounted all the way down turning a 13 x 19 K Series aluminum propeller would hit 42 to 43 MPH at 5900 RPM. Calculated slip was under 8 percent. I also recollect that 4000 RPM produced a cruise of about 27 to 28 MPH.
Hitting 42 MPH at 6300 RPM means the same K series type aluminum propeller is slipping about 14 percent. My guess here is that you won't gain anything by raising the motor. The aluminum K series propeller has very little cupping if any and so it won't be able to take advantage of the elevated running position.
I also ran a 13 x 19 K series stainless propeller with the motor mounted all the way down and there was no speed increase but the RPM dropped to 5600 RPM at WOT. I suspect that if I could have raised the motor (difficult because the motor was mounted using the blind holes) I think the boat would have picked up 1 or 2 MPH with the stainless version of the K series propeller.
rong posted 08-02-2011 09:26 AM ET (US)
Interesting. I have a 88 15 Sport with a 04 Yamaha 2 stroke 70hp turning a Yamaha Performance Series SS 13 1/4 X 16. My max RPM has been around 5800. Also, I installed a brand new Yamaha digital tachometer too. I wonder if I have a bad tachometer??
Peter posted 08-02-2011 10:22 AM ET (US)
Is there a switch on the back of the tachometer for the number of poles?
Tom W Clark posted 08-02-2011 10:32 AM ET (US)
The Yamaha F70 and the Yamaha two stoke 70 are different motors that use different gear ratios and have different WOT RPM ranges. 5800 RPM sounds about right.
Peter posted 08-02-2011 10:08 PM ET (US)
The Yamaha F70 and the Yamaha 70 2-stroke use the SAME gear ratio -- 2.33:1. They have different maximum RPM at WOT -- 6000 RPM for the 2-stroke and 6300 RPM for the 4-stroke.
If a 19 inch pitch K-series propeller worked well for a 2-stroke 70, then the 17 inch pitch should work similarly well with the 4-stroke for all heights and trims being equal.
rong posted 08-03-2011 08:44 AM ET (US)
John/Tim,
I'm so envious of you two guy's. I almost pulled the trigger on a new F70. But at the time I got a great deal on a used Yamaha 2 Stroke. I'm sure with the F70 you don't have to carry as much gas. IMO your boat doesn't sit very low either.
BTW, are you the one John that had the Rude 70 4 stroke?
Congratulations on your purchase.
Mike Kub posted 08-03-2011 09:21 AM ET (US)
This ? is for you technically inclined guys. I'm putting the F70 on the 16'7" hull to replace a 1995 75 hp. What prop rec.and could I expect any better performance?Namaste.P.S.How high would be best mounting?
Tohsgib posted 08-03-2011 10:03 AM ET (US)
16 or 17" prop and look here for how high you can go: http://continuouswave.com/ubb/Forum4/HTML/007561.html
JMARTIN posted 08-03-2011 12:16 PM ET (US)
Rong,
Yes, we had an Evinrude 4 stroke made by Suzuki. Big, heavy, we put weight in the bow locker, lots of weight. I am really amazed at the difference this new motor makes on the way the Sport handles. It's like a new boat. Less weight on the stern and the bow.
John
pcrussell50 posted 08-03-2011 06:19 PM ET (US)
J,
When you put weight up front to balance a heavy motor, did youd do it because even with trim, you couldn't get the bow down? I'm not sure I'd want the sacrifice in speed, m'self... unless you are in a rough ocean, like the Pacific, and will never get near top speed anyway.
-Peter
JMARTIN posted 08-03-2011 06:45 PM ET (US)
No, the weight in the bow was only to make the boat sit more level on it's mooring. I did not need the weight when I was running.
John
pcrussell50 posted 08-03-2011 07:51 PM ET (US)
And you caved in to practicality? Wimp.
j/k of course. Well, the newbie (me) found another acorn. Ive never had a moored boat, and had frankly never consdered the value of a level float while moored. Makes good sense though. Good stuff.
-Peter

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Author	Topic: 2010 F70 speed results on a 15 Sport
JMARTIN	posted 07-29-2011 02:12 PM ET (US) This was not a real accurate, controlled test. I taped a Tom Tom to the dash and tried to read it and the tach and not run into anything. 1983 Sport 15, lots of layers of bottom paint, keel guard, 8 gallons of gas, and myself @ 140lbs. The boat probably has some extra water weight in it. The heron did not stay around for the test. http://i34.photobucket.com/albums/d137/jmartin-/DSCF9225.jpg rpm mph 1000 4 2000 7 3000 16 3500 21 4000 25 5000 33 5500 36/37 6350 42 K 13 x 19 prop, one hole left to go up and I am sure it will handle one more hole up, but it holds so well now, I am going to leave it. The prop looks like aluminum to me. I have a picture of it somewhere. John
JMARTIN	posted 07-29-2011 02:19 PM ET (US) Picture of the prop. The work order shows "use K 13 x 19 series prop" the invoice shows part # 6E5-45941-00-EL, description AL.PROP, 13x19 http://i34.photobucket.com/albums/d137/jmartin-/DSCF8072.jpg John
tedious	posted 07-30-2011 05:44 AM ET (US) Thanks John! Your figures match the one reading I got at about 3700 RPM / 23 MPH / 10 MPG, before I was done in by the bad fuel connection. I don't think my boat has extra weight in it, but given the sensitivity of the 15 to weight, the additional 100 pounds of weight in me will probably make a difference:-). Tim
Tohsgib	posted 07-31-2011 10:00 AM ET (US) If invoice says K series I would check back with dealer as the K is a SS prop I believe. If so you cgot short changed. Honestly I would work on props, 42 with a 70 is about 4-5mph short and a 60 can do that.
Peter	posted 07-31-2011 10:46 AM ET (US) That is a K series aluminum propeller. "K" does not mean stainless steel.
Keeper	posted 07-31-2011 09:15 PM ET (US) Thanks for the intel. Good stuff !
Tohsgib	posted 08-01-2011 10:45 AM ET (US) My Bad...talk to Tom Clark and buy what he recommends.
Tom W Clark	posted 08-01-2011 03:45 PM ET (US) There are aluminum "K" series props and there are stainless steel "K" series props. The "K" simply refers to props made for intermediate gearcase motors. The propeller John has is aluminum. There are better props out there.
JMARTIN	posted 08-01-2011 04:30 PM ET (US) If my goal was to go faster, I would raise to the last hole and get a stainless propeller. Since this boat pulls tubes, wake boards, skiers and is used in some rough conditions, I will stay with what I got until the prop gets dinged up, which it will. Sure, a stainless would be better, but this one is bought and paid for and it is a shared boat. The hole shot is incredible and I have never lost grip with severe trimming and hard turns. On speed runs with lots of trim, you can hear the prop "howl" when you back down. It is really trimmed up, probably too far, which leads me to believe I can go up to the last hole with no detrimental effect on propeller grip. There is some uncomfortable chine walking sometimes at WOT. Trim and wind conditions help eliminate the walking. John
Peter	posted 08-01-2011 08:02 PM ET (US) As a reference, my SuperSport 15 with a 2003 Yamaha 70 2-stroke (same 2.33:1 gear ratio as the F70) mounted all the way down turning a 13 x 19 K Series aluminum propeller would hit 42 to 43 MPH at 5900 RPM. Calculated slip was under 8 percent. I also recollect that 4000 RPM produced a cruise of about 27 to 28 MPH. Hitting 42 MPH at 6300 RPM means the same K series type aluminum propeller is slipping about 14 percent. My guess here is that you won't gain anything by raising the motor. The aluminum K series propeller has very little cupping if any and so it won't be able to take advantage of the elevated running position. I also ran a 13 x 19 K series stainless propeller with the motor mounted all the way down and there was no speed increase but the RPM dropped to 5600 RPM at WOT. I suspect that if I could have raised the motor (difficult because the motor was mounted using the blind holes) I think the boat would have picked up 1 or 2 MPH with the stainless version of the K series propeller.
rong	posted 08-02-2011 09:26 AM ET (US) Interesting. I have a 88 15 Sport with a 04 Yamaha 2 stroke 70hp turning a Yamaha Performance Series SS 13 1/4 X 16. My max RPM has been around 5800. Also, I installed a brand new Yamaha digital tachometer too. I wonder if I have a bad tachometer??
Peter	posted 08-02-2011 10:22 AM ET (US) Is there a switch on the back of the tachometer for the number of poles?
Tom W Clark	posted 08-02-2011 10:32 AM ET (US) The Yamaha F70 and the Yamaha two stoke 70 are different motors that use different gear ratios and have different WOT RPM ranges. 5800 RPM sounds about right.
Peter	posted 08-02-2011 10:08 PM ET (US) The Yamaha F70 and the Yamaha 70 2-stroke use the SAME gear ratio -- 2.33:1. They have different maximum RPM at WOT -- 6000 RPM for the 2-stroke and 6300 RPM for the 4-stroke. If a 19 inch pitch K-series propeller worked well for a 2-stroke 70, then the 17 inch pitch should work similarly well with the 4-stroke for all heights and trims being equal.
rong	posted 08-03-2011 08:44 AM ET (US) John/Tim, I'm so envious of you two guy's. I almost pulled the trigger on a new F70. But at the time I got a great deal on a used Yamaha 2 Stroke. I'm sure with the F70 you don't have to carry as much gas. IMO your boat doesn't sit very low either. BTW, are you the one John that had the Rude 70 4 stroke? Congratulations on your purchase.
Mike Kub	posted 08-03-2011 09:21 AM ET (US) This ? is for you technically inclined guys. I'm putting the F70 on the 16'7" hull to replace a 1995 75 hp. What prop rec.and could I expect any better performance?Namaste.P.S.How high would be best mounting?
Tohsgib	posted 08-03-2011 10:03 AM ET (US) 16 or 17" prop and look here for how high you can go: http://continuouswave.com/ubb/Forum4/HTML/007561.html
JMARTIN	posted 08-03-2011 12:16 PM ET (US) Rong, Yes, we had an Evinrude 4 stroke made by Suzuki. Big, heavy, we put weight in the bow locker, lots of weight. I am really amazed at the difference this new motor makes on the way the Sport handles. It's like a new boat. Less weight on the stern and the bow. John
pcrussell50	posted 08-03-2011 06:19 PM ET (US) J, When you put weight up front to balance a heavy motor, did youd do it because even with trim, you couldn't get the bow down? I'm not sure I'd want the sacrifice in speed, m'self... unless you are in a rough ocean, like the Pacific, and will never get near top speed anyway. -Peter
JMARTIN	posted 08-03-2011 06:45 PM ET (US) No, the weight in the bow was only to make the boat sit more level on it's mooring. I did not need the weight when I was running. John
pcrussell50	posted 08-03-2011 07:51 PM ET (US) And you caved in to practicality? Wimp. j/k of course. Well, the newbie (me) found another acorn. Ive never had a moored boat, and had frankly never consdered the value of a level float while moored. Makes good sense though. Good stuff. -Peter