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Author Topic:   Speed of 13' Whaler

WetWilly389 posted 04-11-2003 12:03 PM ET (US)
I have a portable GPS and some other thing (not sure what it is) that tells me the speed of my 1984 13' SS BW. The two devices give me differnt numbers, they usually vary by about 8-12 mph. I have a 1988 40 HP Suzuki. I was just curious what the top speed would be with just me and no gear in it. Thanks
T_Bro posted 04-11-2003 01:13 PM ET (US)
Willy,
I have an '86 13 Supersport with a '96 40hp Evinrude on it. The engine has a doelfin mounted on it and the speedometer on the boat does not work. The Garmin Map 76 that I use on the boat indicates the top speed on flat water with just me (225 lbs) is around 33 mph. At this speed, the tachometer is registering 5500 rpm, or WFO.
I have just added a Raymarine fishfinder with a paddle wheel on the transducer for a second way to determine the speed, but I think the GPS is the most accurate. If the second device you are describing is the speedo, I would not rely on it. If it is a depth finder or sounder, they can alos be imprecise. If the GPS is around 30-33 mph, I would rely on it.
Keep an eye on your tachometer. If you cant hit 5500 rpm at full open, you may need a different prop.
Buena suerte,
T-Bro
witsendfl posted 04-11-2003 01:47 PM ET (US)
72 Sourpuss w/ 97 40 HP Merc
+ me 250ish 38-40 MPH FAST !!!
witsendfl JimK
Mullet posted 04-11-2003 01:56 PM ET (US)
I too am about 250, 1968 13' with a 99 Merc 40hp = about 38-40. I guess it feels faster with my rear end that close to the water.
JBCornwell posted 04-11-2003 02:10 PM ET (US)
Ahoy, Willy.
Unless you have excess load, prop problems or rigging problems you should get about 1 mph per HP from a 13.
Pitot and waterwheel speedos are notoriously inaccurate unless carefully installed and calibrated.
If your GPS says one thing and other instruments say something else, trust the GPS.
Red sky at night. . .
JB
Bigshot posted 04-11-2003 03:00 PM ET (US)
GPS does not lie. To get an accurate reading run one direction and then the other and avg the 2. Reason being if you are going into a 5mph current the GPS will only show your "land speed" and thus give you an inaccurate reading. You are only going that fast but.....your boat would be 5mph faster if no current. I would doubt you would see much more than 34mph. I know some claim 40mph but I have yet to see a 13' with a 50hp break 38 yet.
Island Bwoy 420 posted 04-12-2003 02:37 AM ET (US)
Hey bigshot, I am putting a 55 hp Evinrude on my sourpuss. Ill let ya know how she goes!
Over the LINE posted 04-12-2003 09:13 PM ET (US)
Bigshot, broke the 40 mark today. As a matter of (GPS) fact I got 44mph out of mine today. It took four tries to get the prop right and putting a jackplate on and taking it off again, but I finally got everything I think I can get out of the boat. This was an averaged run up and down a canal. I am running an '84 13' Sport. It weighs in at 700# plus me (185) and 10 gallons of fuel. I am running a 50hp Yamaha with a 10-1/4 x 15 Yamaha SS prop. The motor is mounted without a jackplate but is about 1-1/2" raised. The motor is turning right at 5500 RPM. I could hold this speed only long enough to read the GPS and then I had to throttle back (it was getting a little out of control).
captbone posted 04-13-2003 10:11 PM ET (US)
The new 13 sports do 44 mph out of the box even with the 40 EFI 4 stroke.
Perry posted 04-13-2003 11:21 PM ET (US)
According to Boston Whaler's performance data of 2002, the 13 sport with 40 Merc classic does 33.3 mph and with the 40 4 stroke 35.5 mph.
logan posted 04-13-2003 11:58 PM ET (US)
I get about 25 knots out of my 93 Suzuki dt40 at wot, With just my self (270) and about 28 gallons of fuel. (and a soggy old boat)
My thoughts on using various means to decide speed are that a GPS will tell you how fast you are moving over a map. Your speedometer (depth finder) will tell you (with varying degrees of accuracy) how fast you are moving through the water. so to get a good GPS reading you would have to run at slack tide in an area without curent or do a few runs back and forth and take an avrage of the speeds to get a close guess of speed)
Bigshot posted 04-14-2003 10:18 AM ET (US)
Guys maybe you have experimental engines or hulls but it aint happening. A 15" pitch at 5500 rpm with NO slip will yield "theoretically" 42.2mph with a 1.85 gear ratio. It is IMPOSSIBLE to have no slip. With a meager 10% slip(which a 13' will have more), you would only do 38mph. A 15 with a 70 will only do 45-47 and that has a modified v. With a 50hp it will do about 36-38. 13's are SLOWER than 15's with 25hp and up. Please advise how you can get 44mph, you are breaking the rules of physics.
PSW posted 04-14-2003 10:37 AM ET (US)
I am going to agree with Bigshot on this one. I grew up using a 13 whaler with a 50 Mercury. I just don't think you can get over 40 with that setup. When testing speed I would not use anything other than GPS. I used to think speedo's were pretty good judge, which they can be under 80% of WOT, but once you start chine walking sounder and speedo are useless. I just don't think some classic whaler hulls are meant to go very fast. The Montauk I have with a 115 Merc and new SS still probably wont touch 50 on the GPS unless I jackplate the motor and forget about skiing, holeshot, and static trim. The hull just does not want to let it and I am learning to accept that...slowly.
PSW
BQUICK posted 04-14-2003 11:57 AM ET (US)
You guys make me chuckle.
A 13 footer slower than a 15?
A 13 footer not capable of of 40 mph?
I guess I have been disproving the laws of physics for the past 30 years going 44-51 in a 13 w/50 Merc.
I guess power trim allows me to turn the boat into something it was not meant to be.
Bruce
Over the LINE posted 04-14-2003 01:16 PM ET (US)
I'm pretty sure I am capable of accurately reading my tach. I am also confident that I can read my GPS. The number 50 on the side of my motor is pretty hard to miss. I just picked the prop up last week so I hope it is what I paid for. I know that I went for a "prop tuning" ride on Saturday. I know that my GPS read 46.8mph one way and 42.4mph the other. I am sure that no one on this forum has seen my boat nor were you along for the ride.
Bigshot posted 04-14-2003 02:02 PM ET (US)
Cool....we have solved a major issue, every prop calculator on the net is wrong. Sorry to argue this without actually being there but this is real simple guys:
Think of a prop as screw. The pitch is the theoretical distance the prop should move through the water in 1 revolution. A 15" pitch prop would move 15". The theoretical speed is figured by multiplying the pitch x engine rpm and dividing by (gear reduction x 12) = feet per minute. Divide by 5280 = Miles per minute, multiply x 60 = miles per hour. This can be shortened to (Pitch x RPM) / (Reduction x 1056) = MPH.
Slip is figured by comparing this theoretical speed to the actual measured speed.
Yamaha 50 has a 1.85 gear ratio, 15" prop, and 5500rpms....is my data correct.
So both of your boats have negative slip.....Einstein would be puzzled.
Now most 30hp run a 13' at 30-33mph. Most 40's turn 33-35mph, do you really think 10hp is gonna fetch you 10mph? I am impressed if it does, maybe that is why they only rated them for 40hp because a 50 would push them way too fast.
Swellmonster posted 04-14-2003 02:13 PM ET (US)
24 beers in a case, 24 hours in a day, coincedence? I think not.
If your body disapates a can of beer an hour, then can we drink a 12-pack throughout the day on the beach and be sober when we leave?
Bigshot posted 04-14-2003 02:15 PM ET (US)
NOPE! You will have a blood/alcohol level under 0.1 but that does not necessarily mean you are sober, just legal.
BQUICK posted 04-14-2003 03:02 PM ET (US)
No fighting kids......:)
I think alot depends on the setup. 2 people and trim and/or prop not optimized, sure my 50 MERC might only run 38 mph.
Well I'm running a 17in cupped, 3 blade, hi-rake Quicksilver prop and turning 5800 rpm.
19 in 3 blade killed it not enough rpm.
2 blade bronze 17in ran 6000 rpm and a couple mph better but only with light load.
Slippage is pretty low with only a few feet of Whaler in the water.
BTW my speeds are not GPS but are with a tournament (ski) Aquameter calibrated speedo verified by the US Coast Guard, Natural Resources Police and the Commandant of the US Navy himself. :)
Yes, I've seen 2 cyl OMC 50 that only ran 37 mph or so lightly loaded. But that's why I run a MERC.
Bruce
captbone posted 04-14-2003 07:00 PM ET (US)
You guys and you great formulas! I guess I was dreaming when Boat test magazine ( tv show after shipshape) did the test on the 13 sport with the 40 four stroke. They had it on GPS at over 42 mph without anything special. Find the episode and then bring your formula and you can say your sorry.

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Author	Topic: Speed of 13' Whaler
WetWilly389	posted 04-11-2003 12:03 PM ET (US) I have a portable GPS and some other thing (not sure what it is) that tells me the speed of my 1984 13' SS BW. The two devices give me differnt numbers, they usually vary by about 8-12 mph. I have a 1988 40 HP Suzuki. I was just curious what the top speed would be with just me and no gear in it. Thanks
T_Bro	posted 04-11-2003 01:13 PM ET (US) Willy, I have an '86 13 Supersport with a '96 40hp Evinrude on it. The engine has a doelfin mounted on it and the speedometer on the boat does not work. The Garmin Map 76 that I use on the boat indicates the top speed on flat water with just me (225 lbs) is around 33 mph. At this speed, the tachometer is registering 5500 rpm, or WFO. I have just added a Raymarine fishfinder with a paddle wheel on the transducer for a second way to determine the speed, but I think the GPS is the most accurate. If the second device you are describing is the speedo, I would not rely on it. If it is a depth finder or sounder, they can alos be imprecise. If the GPS is around 30-33 mph, I would rely on it. Keep an eye on your tachometer. If you cant hit 5500 rpm at full open, you may need a different prop. Buena suerte, T-Bro
witsendfl	posted 04-11-2003 01:47 PM ET (US) 72 Sourpuss w/ 97 40 HP Merc + me 250ish 38-40 MPH FAST !!! witsendfl JimK
Mullet	posted 04-11-2003 01:56 PM ET (US) I too am about 250, 1968 13' with a 99 Merc 40hp = about 38-40. I guess it feels faster with my rear end that close to the water.
JBCornwell	posted 04-11-2003 02:10 PM ET (US) Ahoy, Willy. Unless you have excess load, prop problems or rigging problems you should get about 1 mph per HP from a 13. Pitot and waterwheel speedos are notoriously inaccurate unless carefully installed and calibrated. If your GPS says one thing and other instruments say something else, trust the GPS. Red sky at night. . . JB
Bigshot	posted 04-11-2003 03:00 PM ET (US) GPS does not lie. To get an accurate reading run one direction and then the other and avg the 2. Reason being if you are going into a 5mph current the GPS will only show your "land speed" and thus give you an inaccurate reading. You are only going that fast but.....your boat would be 5mph faster if no current. I would doubt you would see much more than 34mph. I know some claim 40mph but I have yet to see a 13' with a 50hp break 38 yet.
Island Bwoy 420	posted 04-12-2003 02:37 AM ET (US) Hey bigshot, I am putting a 55 hp Evinrude on my sourpuss. Ill let ya know how she goes!
Over the LINE	posted 04-12-2003 09:13 PM ET (US) Bigshot, broke the 40 mark today. As a matter of (GPS) fact I got 44mph out of mine today. It took four tries to get the prop right and putting a jackplate on and taking it off again, but I finally got everything I think I can get out of the boat. This was an averaged run up and down a canal. I am running an '84 13' Sport. It weighs in at 700# plus me (185) and 10 gallons of fuel. I am running a 50hp Yamaha with a 10-1/4 x 15 Yamaha SS prop. The motor is mounted without a jackplate but is about 1-1/2" raised. The motor is turning right at 5500 RPM. I could hold this speed only long enough to read the GPS and then I had to throttle back (it was getting a little out of control).
captbone	posted 04-13-2003 10:11 PM ET (US) The new 13 sports do 44 mph out of the box even with the 40 EFI 4 stroke.
Perry	posted 04-13-2003 11:21 PM ET (US) According to Boston Whaler's performance data of 2002, the 13 sport with 40 Merc classic does 33.3 mph and with the 40 4 stroke 35.5 mph.
logan	posted 04-13-2003 11:58 PM ET (US) I get about 25 knots out of my 93 Suzuki dt40 at wot, With just my self (270) and about 28 gallons of fuel. (and a soggy old boat) My thoughts on using various means to decide speed are that a GPS will tell you how fast you are moving over a map. Your speedometer (depth finder) will tell you (with varying degrees of accuracy) how fast you are moving through the water. so to get a good GPS reading you would have to run at slack tide in an area without curent or do a few runs back and forth and take an avrage of the speeds to get a close guess of speed)
Bigshot	posted 04-14-2003 10:18 AM ET (US) Guys maybe you have experimental engines or hulls but it aint happening. A 15" pitch at 5500 rpm with NO slip will yield "theoretically" 42.2mph with a 1.85 gear ratio. It is IMPOSSIBLE to have no slip. With a meager 10% slip(which a 13' will have more), you would only do 38mph. A 15 with a 70 will only do 45-47 and that has a modified v. With a 50hp it will do about 36-38. 13's are SLOWER than 15's with 25hp and up. Please advise how you can get 44mph, you are breaking the rules of physics.
PSW	posted 04-14-2003 10:37 AM ET (US) I am going to agree with Bigshot on this one. I grew up using a 13 whaler with a 50 Mercury. I just don't think you can get over 40 with that setup. When testing speed I would not use anything other than GPS. I used to think speedo's were pretty good judge, which they can be under 80% of WOT, but once you start chine walking sounder and speedo are useless. I just don't think some classic whaler hulls are meant to go very fast. The Montauk I have with a 115 Merc and new SS still probably wont touch 50 on the GPS unless I jackplate the motor and forget about skiing, holeshot, and static trim. The hull just does not want to let it and I am learning to accept that...slowly. PSW
BQUICK	posted 04-14-2003 11:57 AM ET (US) You guys make me chuckle. A 13 footer slower than a 15? A 13 footer not capable of of 40 mph? I guess I have been disproving the laws of physics for the past 30 years going 44-51 in a 13 w/50 Merc. I guess power trim allows me to turn the boat into something it was not meant to be. Bruce
Over the LINE	posted 04-14-2003 01:16 PM ET (US) I'm pretty sure I am capable of accurately reading my tach. I am also confident that I can read my GPS. The number 50 on the side of my motor is pretty hard to miss. I just picked the prop up last week so I hope it is what I paid for. I know that I went for a "prop tuning" ride on Saturday. I know that my GPS read 46.8mph one way and 42.4mph the other. I am sure that no one on this forum has seen my boat nor were you along for the ride.
Bigshot	posted 04-14-2003 02:02 PM ET (US) Cool....we have solved a major issue, every prop calculator on the net is wrong. Sorry to argue this without actually being there but this is real simple guys: Think of a prop as screw. The pitch is the theoretical distance the prop should move through the water in 1 revolution. A 15" pitch prop would move 15". The theoretical speed is figured by multiplying the pitch x engine rpm and dividing by (gear reduction x 12) = feet per minute. Divide by 5280 = Miles per minute, multiply x 60 = miles per hour. This can be shortened to (Pitch x RPM) / (Reduction x 1056) = MPH. Slip is figured by comparing this theoretical speed to the actual measured speed. Yamaha 50 has a 1.85 gear ratio, 15" prop, and 5500rpms....is my data correct. So both of your boats have negative slip.....Einstein would be puzzled. Now most 30hp run a 13' at 30-33mph. Most 40's turn 33-35mph, do you really think 10hp is gonna fetch you 10mph? I am impressed if it does, maybe that is why they only rated them for 40hp because a 50 would push them way too fast.
Swellmonster	posted 04-14-2003 02:13 PM ET (US) 24 beers in a case, 24 hours in a day, coincedence? I think not. If your body disapates a can of beer an hour, then can we drink a 12-pack throughout the day on the beach and be sober when we leave?
Bigshot	posted 04-14-2003 02:15 PM ET (US) NOPE! You will have a blood/alcohol level under 0.1 but that does not necessarily mean you are sober, just legal.
BQUICK	posted 04-14-2003 03:02 PM ET (US) No fighting kids......:) I think alot depends on the setup. 2 people and trim and/or prop not optimized, sure my 50 MERC might only run 38 mph. Well I'm running a 17in cupped, 3 blade, hi-rake Quicksilver prop and turning 5800 rpm. 19 in 3 blade killed it not enough rpm. 2 blade bronze 17in ran 6000 rpm and a couple mph better but only with light load. Slippage is pretty low with only a few feet of Whaler in the water. BTW my speeds are not GPS but are with a tournament (ski) Aquameter calibrated speedo verified by the US Coast Guard, Natural Resources Police and the Commandant of the US Navy himself. :) Yes, I've seen 2 cyl OMC 50 that only ran 37 mph or so lightly loaded. But that's why I run a MERC. Bruce
captbone	posted 04-14-2003 07:00 PM ET (US) You guys and you great formulas! I guess I was dreaming when Boat test magazine ( tv show after shipshape) did the test on the 13 sport with the 40 four stroke. They had it on GPS at over 42 mph without anything special. Find the episode and then bring your formula and you can say your sorry.