speed at WOT for a 50HP?

[JT!]

i've been down on the river running the old boat and my top speed is 42km per hour. (26mph) (motor: evinrude lark selectric 50 1971)

isnt that slow?

1) are there patches under the boat? yes
2) is the propellor chipped or damaged? yes
3) does the tank almost empty itself after 4 hours of trolling? yes


i know i should sand the bottom smooth, i should replace the prop.

which should i fix first? prop or bottom of boat?
how long should a 25L ~6GAL of fuel last in a 1960's arkansas traveller, not heavily loaded?

how fast should i be able to go is glass calm water? it felt like im pushing a bathtub at slower speeds.

thanks.​

 

[JB]

Re: speed at WOT for a 50HP?

"old boat" is just too vague, JT. Tell us more.

 

[JT!]

Re: speed at WOT for a 50HP?

here is a picture:


1963 Skijack 15.5 ft

 

[jimmbo]

Re: speed at WOT for a 50HP?

Is the bottom of the ull straight? My uncle had the the 16 arkanas traveler and it had a hook as well as a rocker. It only did 33 with a 90hp.

 

[Silvertip]

Re: speed at WOT for a 50HP?

At wide open throttle, the engine will consume approximately 5 gallons of fuel per hour. There is no way to calculate how much it will burn at throttle settings less than that but 3-1/2 at 2/3 throttle would be in the ball park. The consumption you mentioned for trolling seems a tad high. Remember, that engine was built when fuel was cheap. Economy and the environment were not issues.

 

[LORDY611]

Re: speed at WOT for a 50HP?

And that boat wasnt light when it was new. Now it has probably added a "few" pounds over the years (haven't we all?) from water weight gain, and the motor is likely not up to it's peak performance like back in the day. The combination may just be what it is showing you: a bit of a tired combo in terms of performance and efficiency. As previous posts may have said, clean up the bottom, lightly dress the prop with a file if there are a few nicks. Those will definitely help. Somewhere in Google you should be able to find out what effect on hull speed various amounts of algae growth have. You would be surprised. The hull may be your first target.

 

[tashasdaddy]

Re: speed at WOT for a 50HP?

that is a heavy boat, for it's size. to get that lapstrake design requires more glass than you would think. properly tuned, good prop, bottom cleaned up, i would expect 30'sh.

 

[Joe Dirt]

Re: speed at WOT for a 50HP?

I don't think that for the HP rating of your motor, the age and condition of the boat and hull, that MPH is out of line.

What speed do you think it should be running?

 

[JT!]

Re: speed at WOT for a 50HP?

26mph is slower than i thought a 50hp could do, even an old one. im not disappointed. but fuel consumption! wow it takes double what my minivan uses in an hour. and the van will go 40x further.

as for algea slowing a boat down. hmm. mine has a few square feet of fibercloth some wiseguy slapped on before i got it. unsanded as well. so no wonder.

i was thinking of building a Jimbo 16' from glen-l or a similar design, if i put my 50hp on that i hope to get better mileage and speed and enjoyment?​

 

[EricR]

Re: speed at WOT for a 50HP?

Should do a tad faster, but without a tach showing what RPM it's turning it can be hard to say.

I have a 15' 1969 Glasspar runabout, a vee hull, fairly constant deadrise. With the wife and two small kids it will do right on 30mph at 6000 RPM with a mid 90's 45 horse Honda, that's rated power at the prop. I am running a stock 11 1/4 X 13 three blade aluminum prop. I need to raise the enige an inch on the transom but can't until I re drill it.

Your old 50 is probably more like 43-45 horse at the prop. You may be suprised how much better yours may run with a fresh prop, those little nicks and dings add up and take away pitch and efficiency.

 

[EricR]

Re: speed at WOT for a 50HP?

Should do a tad faster, but without a tach showing what RPM it's turning it can be hard to say.

I have a 15' 1969 Glasspar runabout, a vee hull, fairly constant deadrise. With the wife and two small kids it will do right on 30mph at 6000 RPM with a mid 90's 45 horse Honda, that's rated power at the prop. I am running a stock 11 1/4 X 13 three blade aluminum prop. I need to raise the enige an inch on the transom but can't until I re drill it.

Your old 50 is probably more like 43-45 horse at the prop. You may be suprised how much better yours may run with a fresh prop, those little nicks and dings add up and take away pitch and efficiency.

I also see the hull you have has round chines (rounded at the waterline in the stern) rather than being a sharp edge. This aids cornering, but slows you down as the water does not cleanly "get away" from the hullsides as you plane.

 

[jimmbo]

Re: speed at WOT for a 50HP?

Ski jack 15 weighed 630 lbs when new