1975 40hp evinrude

[brickman64]

How do I know what prop to buy for a 1975 40hp evinrude 4005c?

 

[brickman64]

Re: 1975 40hp evinrude

how do i know what prop to buy for a 1975 40hp evinrude 4005c?

bump.

 

[steelespike]

Re: 1975 40hp evinrude

Please read"read this first" at the top of the page.get us as much info as possible.wot"wide open throttle",rpm and speed
are a must.A gps for speed and a TinyTach for rpm.Tiny tach will work on any motor.
Tell us about your setup.I can tell you according to a1975 brochure it came with a
13" pitch prop.That is a high pitch for that year. Intended for a relatively light boat.

 

[brickman64]

Re: 1975 40hp evinrude

Well it is on a 1972 14' starcraft and it is light,there is no tach or a way to measure speed just an old fishing boat,I would be happy to measure anything but it came with an eaten up prop impossible to determine size,so other than the size of boat i cannot come up with any other info.

 

[brickman64]

Re: 1975 40hp evinrude

Also if you add a couple guys even though the boat is light 2 men can add 400 or more lbs to the load,if thats the case then what should i get beside a 13" pitch? Also I tried to get a measurement in the existing prop don't know if 8 1/2" makes sense to anyone but thats what I came up with. Please give any input.Thanks

 

[steelespike]

Re: 1975 40hp evinrude

Your prop size is probably under the prop nut.
If the boat is a bare utility with tiller steering no floors live wells windshield or steering wheel then a 13" pitch should work
other wise a 12".If you put 2 or 3 guys in the boat the light 14 probably needs a 12"
A Tinytach for about $47 is easy to install and will work on just about any motor 1cyl or 21 cylinder.Perhaps you could borrow a gps for speed.Tach can be hand held or installed.
All this assumes the motor is healthy and the setup is correct.
You can measure diameter from the center of the bore to the tip of one blade and double the number.
A prop intended for that motor will be the right diameter.
That little boat won't do as well with a load as a 16 or 18ft light utility.
If a light 14 a healthy 40 hp could reach mid to upper 30s.lightly loaded.

 

[brickman64]

Re: 1975 40hp evinrude

ok I have found out some other info , the original part number is 386841 , this is a pin drive not a spline , it is a 11 3/4" x17" but i believe 17" is not the pitch i want simply because when someone is in the back seat it doggs down real bad.Any ideas on what to get?

 

[steelespike]

Re: 1975 40hp evinrude

The motor came with a 13, a 14 was the biggest listed in the 75 brochure.
The only sizes available here 11 1/2" or 12" Is the boat a bare utility with tiller steering?
Not knowing your wot rpm makes any prop selection purely in the dark guess.
I sure wouldn't think anything bigger than a 14" would work.
Over time too high a prop could cause premature motor problems and poor performance.Too low a number could cause sudden
self destruction.