Re: [omc-boats]Top Speed variables

If a boat's weight isn't supported by the trailer supports properly, the
hull bottom can hook or sag and change the performance.

Most likely, if your boat has always sat on the Evinrude trailer designed
for it, then it's probably OK.

Just the same, I always loosen the tie-down tension in storage to reduce the
possibility.

Not a lot one can afford to do when this occurs. In the speed calculator you
would reduce the efiiciency number slightly lower on the hull from new.

Lee

----- Original Message -----
From: "Willie Anderson" <willie@...>
To: <omc-boats@...>
Sent: Monday, September 25, 2006 10:04 PM
Subject: RE: [omc-boats]Top Speed variables

> In point 2, you mentioned trailer "hooking". What exactly is that? My
> hull deforms a bit were it sits in the rollers. Is that normal or a sign
> of money yet to be spent?
>
> Thanks,
> Willie.
>
> 68 Sportsman 155.
>
> -----Original Message-----
> From: owner-omc-boats@...
> [mailto:owner-omc-boats@...]On Behalf Of lib1@...
> Sent: Monday, September 25, 2006 10:48 PM
> To: omc-boats@...
> Subject: Re: [omc-boats]Top Speed variables
>
>
> RE: Subject of Top Speed.
>
> You didn't say where you live, or which motor is in your Sportsman, but
> let's assume it's a 155 and you live 1000 ft ASL.
>
> 1) First start by getting the boat as light as possible. The 40 mph
> factory
> claim was with no extra gear and a 170 pound average weight pilot. You can
> even go weigh the boat and trailer on a public scale (disconnected from
> your
> tow vehicle). If you have the Evinrude trailer and the fuel tank is less
> than half full you should see something around 1850 - 1900 lbs on the boat
> and 400 to 500 on the trailer for a total boat, v6 motor, and trailer of
> around 2200 to 2400 lbs. The boat may have gained weight from water below
> the floor, but most likely you're lugging several hundred pounds of
> "stuff"
> around. Weight is the most common speed killer.
>
> 2) Next be sure and check the condition of the hull bottom for excess
> drag.
> Wax and buff it out if possible. Always do you top speed runs in calm
> water
> with no winds. Try to make your runs in opposite directions, to cancel out
> wind or currents. Dirty bottoms are also a speed killer. You 69 hull is
> slightly (5 percent) more efficient that the 64 - 68 Sportsmans, but that
> can get quickly offset with any crap on the bottom or deformation of the
> hull due to trailer "hooking."
>
> 3) What is your altitude above sea level? Your horsepower is reduced 4 %
> for
> every 1000 ft above sea level. For example, at 1500 ft you lose 6 percent,
> no way around it. At 6000 ft ASL where I boat, I lose 24 percent of the
> available hp. But where I live , we understand the effects of air
> density,
> most people never take it into consideration, unless they are an aircraft
> pilot flying out West.
>
> 4) Check your speedometer accuracy against a GPS. The old pitot
> speedometers are usually pretty accurate when held at a steady, on-plane,
> speed in smooth waters. Check your tach accuracy against another just for
> good measure, as well. We used to measure off a known distance and clock
> timed runs for determining accurate speed, but now with GPS that's a bit
> old
> fashioned.
>
> 5) If your engine is truly only able to turn a true 3800 rpm, then you
> should consider swinging a smaller pitch prop. The 16-footers usually came
> with a 16-inch-pitch prop, verify the pitch by getting the number off of
> the
> prop. They range from 12 to 20-inch pitch. Your engine, if properly tuned
> should run WOT (wide open throttle) at 4300 to 4500 rpm, with 4400 the
> factory recommended redline. By only turning 3800 you are probably losing
> 15
> % of your power. A two-inch decrease in prop pitch will generally yield
> another 500 rpm at WOT. Also, a stainless steel prop will generally pickup
> 1
> to 2 mph over the aluminum. See Prop part number info at:
> http://hhscott.com/evinrude/choosing_a_prop.htm
>
> 6) Check your gear ratio. It's not unheard of for a previous owner
> swapping
> the sterndrive. It's easy, you count how many revolutions the engine makes
> for one turn of the prop. On a V6 the engine turns 1.5 times for one turn
> of
> the prop. A V8 is close to 1-to-1. IF somehow your V6 is now turning V8
> gears, you won't have the torque to turn "tall" of gearing. And you won't
> be
> able to decrease prop pitch enough. (Of all the variables I've listed,
> this
> last one is least likely.)
>
>
>
> If you are interested in seeing how these variables all can cause your
> boat's top speed to vary greatly, play with the online speed calculator
> at:
>
> http://hhscott.com/evinrude/docs/BSLAC.htm
>
> I plugged in the numbers and 30 - 31 mph is about right for a V6 @... 3800
> RPM
> in a Sportsman, at 1000 ft ASL, with 4 adults on board and a couple
> hundred
> pounds of fuel and gear. My recommendation is try spinning a smaller-pitch
> prop and/or put the boat on a diet.
>
>
> ----- Original Message -----
> From: <ruddfamily4@...>
> To: <omc-boats@...>
> Sent: Monday, September 25, 2006 5:14 PM
> Subject: [omc-boats] MIME-Version: 1.0
>
>
>>I have a 1969 sportsman, i believe i am the 3rd owner and have owned the
>>boat for over 20 years with very little trouble, The only problem i seem
>>to
>>have that re-occurs is the tilt mech. breaks, the clultch doesn't work or
>>doensn't work properly.
>> If i hit anything, the unit raises up but in the process it pushes the
>> worm gear and cap out of the end of the thilt mech. and into the bottom
>> of
>> the lake. Last time it broke some of the alum casting around the
>> retaining
>> ring.
>> I checked some web pages and the worm gear, o ring and brass plug are
>> pretty expensive. This old classic runs well, however i only get about
>> 30mph at 3800 rpm with the v6.
>> I am looking for suggestions to remedy the tilt problem, and suggestions
>> on increaasing the speed to closer to the factory spec of 40mph.
>> thanks for any advice.
>> Keith
>> -----
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Received on Tuesday, 26 September 2006