posted 05-10-2014 05:46 AM ET (US)        

With me and a buddy, 2 trolling motor batteries and a 70# foot control trolling motor on the bow, I can hit 31 knots trimmed out in a lake turning a Stilleto 10.5" x 12" turning 5400rpm.

Today, solo, no trolling motor stuff. Just 9 gallons and a group 24 battery. Bay was blowing, like bad.
Only semi calm water was near the launch between piers. Still bumpy.
Ran both ways, same speed. Tide was slow and across direction of travel.

Used Navionics app on iPhone 5s for speed in knots.
35.1 - 35.3 knots over 6 runs, 3 in each direction. Speedo was around 40 (pitot tube type). Sorry RPM unknown. Trying to have phone angled so I could read it without it falling wasn't easy with one hand on the wheel, one hand on the throttle.

I know. I know.
Impossible.
Prop slip factor.
It's only a 50 HP.

I'm just publishing my results for my rig.

Any comments?

FISHNFF

posted 05-10-2014 10:28 AM ET (US)            

The wind and chop make for the ideal top speed conditions and running light makes it more likely you can take advantage of that. Do not underestimate the effect of weight on boat speed.

Add a good propeller and (probably) a much higher motor mounting height than was used on that boat back in the day, and you can see very significant speed improvement under the right conditions.

But if you did hit 35.2 knots, that motor was turning in excess of 6100 RPM. Its redline is 5500 RPM.

posted 05-10-2014 03:16 PM ET (US)            

I did raise the motor higher to get the lower holes to throughbolt properly.
I am a bit surprised at the performance if this little engine.

posted 05-11-2014 12:57 PM ET (US)            

The Mercury 50-HP was also a 1976 engine, so it was probably rated at the power head. But, given the legend of Mercury performance, I am sure it must have made 50-HP.

I experimented with several propellers of various design, pitch, and diameter.

The fastest I recall going was about 34-MPH measured by GPS receiver. Since I wasn't making long ocean passages, I recorded the speed in statute miles per hour. I never heard of anyone recording speed in nautical miles per hour on a small boat, in part because, as far as I can tell, no speed instruments were ever made for small boats that were calibrated in nautical miles per hour. (This is based on a conversation with a OEM manufacturer of boat instruments; he told me they never even had a request for a speedometer with calibration in nautical miles per hour from any customers.)

Whenever someone begins to cite the speed of their small recreational boat in nautical miles per hour, I have to wonder if they are just being "nautical" or "salty" and really mean statute miles per hour. I don't think anyone ever talked about a 15-foot outboard boat's speed in nautical miles per hour in the past. My guess is that this oddity came about when a few GPS receivers offered the option of using different units of speed, with nautical miles per hour being one of them.

Perhaps there were some paddlewheel type speed indicators that had calibration in nautical miles per hour, but I don't think any Pitot tube speedometers, which typically would be used for speeds in the 40-MPH range, had calibration in nautical miles per hour.

On this basis, I am impressed that a STRIPER 15, a boat probably heavier than my old SPORT 15, can hit 40.5-MPH with 50-HP.

posted 05-11-2014 01:25 PM ET (US)            

http://i.ebayimg.com/00/s/NDgwWDY0MA==/z/xioAAOxygj5Snfwi/$_35.JPG

My iPhone, Garmin handheld GPS and FURUNO GPS Chart Plotter all offer knots as a unit as speed measurement.

posted 05-11-2014 06:52 PM ET (US)            

quote:

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My iPhone, Garmin handheld GPS and FURUNO GPS Chart Plotter all offer knots as a unit as speed measurement.

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Yes, as I mentioned already, it is the availability of GPS receivers--which are employed in all the devices mentioned by Tom-- with the option to use nautical miles per hour as a unit, that seems to have attracted the fancy of so many small recreational boat owners that they now want to tell us their boat speed in knots.

posted 05-11-2014 08:42 PM ET (US)            

What I have observed in many reported measurements of boat speed over time is that conditions play a bigger role than one might think. I have seen my boat go 42-MPH on one day and then 39-MPH the next, with very little having changed on the boat. Also, GPS speed measurements are not absolutely accurate. They often jump around, too. The reading that someone picks out from a series of speeds presented on a GPS receiver while the boat is maintaining a steady speed is usually not a perfect average. It is hard to say if people report the highest number--certainly they don't report the lowest--or if they record ten numbers and average them.

posted 05-14-2014 01:58 AM ET (US)            

My Quicksilver speedo reads in MPH and gets its reading through a pitot tube.

I set up my Garmin FF to read on knots using a paddle wheel.

All my GPS units are set to read in knots.

The Furuno LC-90 Loran I learned to navigate on read in knots.

Just what I'm used to.

Not about my speed claim. I knew it would stir some skepticism. I would be skeptical too. Doesn't seem right,, but let me tell you, I was there.

The speed readings were on 6 runs, 3 each way. The speeds read we're pretty steady, like fluctuating +/- 0.1 knot. Didn't vary more than 0.2 knots either way.

It was very difficult to read all the guages and hang on safely.

I am moving my battery to the port side corner to help offset weight. The fuel tank is located between the 2 pedestal seats and located slightly to port.

I will try to mount my Garmin GPS and take a video with my Contour.
Or you can take it out and try.

And the Merc is a premix, not oil injected. My 1987 Merc catalog shows the 50/60 as injected.

FISHNFF

posted 05-14-2014 10:29 AM ET (US)            

I also read quite a bit including several small powerboat discussion web sites. I have never met anybody in my entire life who objects to the use of knots as a unit of speed measurement for small powerboats. It is a common, though certainly not universal, practice outside of the Detroit Metro area.

Yes Jim, I think your continuing rant against the use of knots as a unit of speed measurement is rather bizarre and a poor use of your time and intellect.

bizarre

posted 05-14-2014 07:46 PM ET (US)            

I will run the boat again tomorrow with the battery moved to port and a bit forward.

I'll stick with the prop I have. I'll just keep an eye on the tach.

FISHNFF

posted 05-14-2014 08:25 PM ET (US)            

As for the meteorological units, I think wind speed in knots is only used in marine forecasts, and probably more of a tradition than anything else. For scientific purposes I suspect that kilometers per hour is probably preferred these days.

posted 05-14-2014 08:49 PM ET (US)            

quote:

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Tom--you might want to broaden your world view, and realize that, just because you are on the West Coast of the USA, you are not smarter than all the country bumpkins back East. It is possible, you might consider, that your opinion does not represent the ultimate experience on all matters related to boating. Thanks if you will give some consideration to that notion, however foreign it might be to you.

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posted 05-14-2014 08:50 PM ET (US)            

You have a long history here of claiming that it is unusual and inappropriate to use knots as a unit of measurement for small powerboats like this 15 foot Whaler. On that point you are wrong, it is neither.

You can use your trademark condescending tone, you can make false claims, like speedometers are not calibrated in knots and you can mock those who try to introduce some sense to the discussion, but you are still wrong on that point.

posted 05-14-2014 09:28 PM ET (US)            

In the modern world there is really not much use for the nautical mile unless you happen to be using paper charts with a Mercator projection. A Mercator chart is a preferred projection for long ocean voyages because of a consistency of heading on the chart. (This is another long sidebar topic I leave unexplored here.) If it is not considered overly presumptuous to say, I don't think too many 15-footers are navigated these days with a paper chart in Mercator projection and some dividers to measure distance. That is the basis for my opinion that most 15-footers are probably not measuring their distance, and hence their speed, in nautical miles per hour, unless they happen to have a GNSS receiver which they have set up to use those units.

There is a bit of irony here, for me, because the unit of speed that a GNSS unit sends via NMEA-0183 datagrams containing speed information is usually a unit of knots, but most display devices provide conversion into other units, usually statute miles per hour or kilometers per hour. The basis for using the knot in a NMEA datagram is probably, again, historical, as otherwise the units of modern data communication are usually scientific units. For example, pressure is not sent in PSI but in units of Pascals.

The regulation of boat speed on most inland lakes, which, if again I am not being to presumptuous, is where many 15-foot boats are operated, is very likely to be universally done in MPH, not KNOTS.

By the way, Wikipedia say that KNOT is used in maritime navigation. The word maritime is a hyperlink in that definition, and it leads to a separate article called "Freight Transport." This is completely in accord with my characterization of the KNOT as being something used on long ocean voyages, that is, voyages by commercial ships engaged in freight transport.

posted 05-14-2014 09:32 PM ET (US)            

quote:

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...Jim...your statement is very similar to something I was going to write earlier.

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posted 05-14-2014 10:01 PM ET (US)            

quote:

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I don't know that I am open to being persuaded that the entire world of recreational boaters is measuring boat speed in KNOTS. The experience here, on this website, is a good example of the opposite. It appears that only a small minority of recreational boaters prefer KNOTS as a speed unit instead of MPH.

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I don't think anybody here has ever suggested that small boat speed only be measured in knots, just that it is not inappropriate to do so.

quote:

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I never met anyone who talks about the speed of their 15-foot outboard boat in terms of KNOTS. But, if they want to, that is fine with me.

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I am relived to hear that Jim. The next time someone reports boat speed in knots (and, of course, you interrogate them about the correct use of that unit of measurement) I will rest assured knowing we will witness no more push-back and mockery from you accusing them of merely trying to be "nautical" or "salty".

posted 05-15-2014 12:35 AM ET (US)            

--in the Evinrude ICON gauges, there is no dial pointer speedometer available with a primary dial face calibration in KNOTS;

--in the Mercury SmartCraft gauges, there is no dial pointer speedometer available with a primary dial face calibration in KNOTS;

--in the Yamaha Pro Series II gauges, there is no dial pointer speedometer available with a primary dial face calibration in KNOTS;

I think that encompasses about 90-percent of the market for modern OEM outboard gauges.

In digital gauges, there typically are options for units of measurement for speed to include MPH, Kilometers-per-hour or KPH, and also nautical-miles-per-hour or KNOTS.

posted 05-15-2014 09:39 AM ET (US)            

You have succeeded, yet again, in derailing a perfectly good topic of discussion with one of your "sidebar" discussions about something neither remarkable nor interesting while silmultaneousy mocking and haraguing other participants in the discussion.

posted 05-15-2014 11:00 AM ET (US)            

Speed is expressed officially in knots when referring to speed/distance here on the salty Chesapeake and even up in brackish (not so salty) Baltimore. Speed limit in the harbor is 6kn.

I'll be using statute miles on the St Lawrance River where I'm headed to tonight. Speed limit between Rock Island and Alexandria Bay, NY is expressed in statute mph. (15mph at night, 35mph daytime)

posted 05-17-2014 02:12 AM ET (US)            

From M-W.COM:

maritime adjective

--of or relating to sailing on the sea or doing business (such as trading) by sea

--located near or next to the sea

posted 05-18-2014 01:57 AM ET (US)            

My tach seemed to be not reading correctly, as it barely turned 5000RPM with my friend Jeff along for the ride..

With 4 nice 10-12# striped bass in the cooler, Jeff held on and read 33.2-33.5knots (38.18 - 38.525 Stature Miles Per Hour) on 3 runs.

Battery still not charging.

posted 05-19-2014 02:56 AM ET (US)            

A few months later, I used the voltage setting on my fish finder and noticed the voltage didn't change whether motor was off or wide open.
I ran a battery (new ACDelco deep cycle starting ) dead when the motor had a difficult time starting during a trip to a lake. Charging it could not get the black indicator eye back to green so it was exchanged.
New one fine. Still not charging.

Where can I find the grey wire coming from the regulator?

posted 05-19-2014 10:15 PM ET (US)            

http://continuouswave.com/cgi-bin/crouchcalc.pl