best work prop for 40 hp evinrude

[phillim]

I have a 1962 Evinrude Lark IV (40 h.p.)Selectric shift pushing a 26 ft work barge with a 3 blade prop.I should mention that there is no size marking on the prop other than an "S" stamped on the hub.The motor runs at about 2000 rpm and goes through the gas at a pretty good rate.Average load on the barge runs from 2000 to 2400 lbs per load.I'm hoping someone has some suggestions.Thanks much

 

[steelespike]

Re: best work prop for 40 hp evinrude

Do you run it at 2000 or is that the best it will do. Is the rpm by the tach?
What year motor?For the health of your motor it needs to be able to rev near its max rpm.
We can determine that by the year.
The forty will use about 4 to 5 gallons per hour at wot.(wide open throttle)Regardless if your pushing the barge or a 10 footer.
So a good tune up may help fuel use.I don't picture the barge changing speed much but we can help the motor feel better.
It needs to rev freely and you can operate it at what ever rpm you want.

 

[jestor68]

Re: best work prop for 40 hp evinrude

You'd want the lowest pitch prop you can find.

For example, Propco Propellers lists a 11 X 9 pitch for a pin drive motor intended for heavy loads such as houseboat/pontoon boat.

 

[steelespike]

Re: best work prop for 40 hp evinrude

Just wondering how we know it's a pin drive non thru hub prop?
"Old Evinrude" doesn't seem like enough information.

 

[jestor68]

Re: best work prop for 40 hp evinrude

Just wondering how we know it's a pin drive non thru hub prop?
"Old Evinrude" doesn't seem like enough information.

Reworded so as not to spark debate.

A newer motor would use a higher minimum pitch due to a different gear ratio.

Regardless; he would need the minimum pitch available for the motor.

 

[steelespike]

Re: best work prop for 40 hp evinrude

Reworded so as not to spark debate.

A newer motor would use a higher minimum pitch due to a different gear ratio.

Regardless; he would need the minimum pitch available for the motor.

agreed.

 

[limitout]

Re: best work prop for 40 hp evinrude

I have this old evinrude pushing a 26 ft work barge with a 3 blade prop.I should mention that there is no size marking on the prop other than an "S" stamped on the hub.The motor runs at about 2000 rpm and goes through the gas at a pretty good rate.Average load on the barge runs from 2000 to 2400 lbs per load.I'm hoping someone has some suggestions.Thanks much

we need to know the year (or a close guess) and the gear ratio of the lower unit if you know it so we can give you more help.

off hand it sounds to me like you are way over pitched in an effort to push more water but the motor needs to get its rpms up higher to provide enough power to push the barge better.

 

[phillim]

Re: best work prop for 40 hp evinrude

Hi Limitout
Sorry, I should have been a little more specific.The motor is a 1962 Evinrude Lark IV Selectric shift.(40 h.p.)As for the gear ratio, that's unknown.I'm burning 3-4 gals of gas an hour,which doesnt sound too bad unless I'm out there for 4-5 hours at a stretch.Any idea on how to find the gear ratio on that motor??
thanks bud,have a great weekend

 

[phillim]

Re: best work prop for 40 hp evinrude

Hi steelespike,
I re-worded the original post.the motor is a 1962 Evinrude Lark IV (40 h.p.)Selectric shift and your right about the pin drive.Gear ratio right now is not known.
Have a great weekend

 

[phillim]

Re: best work prop for 40 hp evinrude

2000 rpm is about half throttle,any more than that does not make any appreciable difference in forward speed,just burns the fuel up quicker
I have to ask....WOT means what exactly.I see WOT in different postings and has me stumped,which doesnt take much sometimes lol

 

[phillim]

Re: best work prop for 40 hp evinrude

Thanks jestor68
A prop shop might be able to tell me whats on the motor now,then I could go from there

 

[steelespike]

Re: best work prop for 40 hp evinrude

WOT = wide open throttle.
Your gear ratio is 1.75:1 (prop turns once for each 1 3/4 revolutions of the motor)
In 62 your motor came with a 10 3/8 X 14 with an exchange for a 11 1/2, 12 1/2 or 13 1/4.
Prop size is always written diameter X pitch.Pitch is the key number.
You need the lowest pitch you can find. 11 X 9" Propco jestor mentioned comes to mind.
You may notice that the diameter is different ;usually as pitch goes down diameter goes up.
I assume your guessing rpm.
With a 9" pitch your motor will rev much more freely.Normally we would suggest a tach to be sure your not over revving
but in your setup this isn't likely.
Look all over your prop for the numbers.Near the base of the blades or possibly on one end of the hub.
Very likely the prop is worn and a little beatup so a new one may be a good investment.