Speedo accuracy? Do they work?

[Chinewalker]

Re: Speedo accuracy? Do they work?

I would say that 30 mph, plus or minus, is probably in the right neighborhood with a Fat Fifty.

As for accuracy, I look at my speedo as a tool. As long as it is consistent in its readings, then I know everything is working as it should. If every time you go out with a given load you reach X-MPH, then you know the rig is working as it should. If for some reason it drops off significantly, then it may be a heads-up that it is time to clean the green beard from the waterline, or take a look at the prop you dinged last time out, or perhaps something else is amiss.

A speedometer, along with a tachometer, helps greatly with propeller selection and set-up, too.

- Scott

 

[jay_merrill]

Re: Speedo accuracy? Do they work?

Nice boat! I have to admit that I wouldn't want the maintenance burden of an old Thonpson, but they are are pretty boats!

 

[sschefer]

Re: Speedo accuracy? Do they work?

Great looking boat!.. Speedo gauges like yours work on air pressure, not water pressure. Altough it is the water being forced into the tube that compresses the air in it and creates the rise in air pressure which causes the needle to move.

Some gauges can be calibrated with an adjustment screw in the back and you can actually get them pretty accurate above 10mph. The fact that they do work on air pressure means that altitude will affect them. On a lake at 5000 feet you'll read differently than you will at sea level.

The fact remains that they are close enough for all but a scientest or a precision navigator. Enjoy it.

 

[wellsc1]

Re: Speedo accuracy? Do they work?

I may be a bit late, but here's mtcw. I agree, GPS is the way to go. Speedometers offer two different readings to me, both unreliable. Going with the water current and going against the current shows lower and higher speeds respectively then actual speed over ground. Hence, speed over water will be different than GPS' speed over ground. Did I explain that clearly? Or am I two cents off my rocker?

 

[bucchb]

Re: Speedo accuracy? Do they work?

I am not familiar with an Evinrude 450. But to get back to your original question of 40 mph with 800lbs.

I doubt any 1958 motor could get this boat going 40 mph??

Then there is the question of whether you would ever WANT to do that in a boat this fine. The stresses at that speed and weight, going over waves or boat chop (let alone going ofshore in the ocean) at that speed is something I wouldn't do.

In my humble, that boat is for pleasure cruising defined in 1958, which would be cruising at 25 - 30 mph, with an occasional, crankup to top end, WHATEVER THAT IS.

Have fun, and realize you have a 50 year old classic, that hopefully you will pass down to someone else.

 

[W_Guy]

Re: Speedo accuracy? Do they work?

Thanks for the nice words gentlemen.
I did buy an Airguide tach recently and plan to install that. I like the idea of a tach as a "safety device" as well as a good way to know where to set the motor for a good plane without having the pedal to the metal (wood) all the time.
I intend to take good care of the old girl and not abuse her. I just bought the boat last month and haven't actually seen it yet in person. It's in IL and I'm in NJ. Therefore I can't answer the question about the trailer axle. I've had the motor checked out and had a new impeller installed. I plan on going out in July for some fun on the water.
Verne