Somebody help me know where to start

[g1vetter]

I bought a used boat with an older Evinrude 2 cylinder 40hp motor. Because the motor is older, the model/serial cannot be read. I was told it is a 1994 model.
Prop that is on it has several nicks and I would like to replace it but I don't see any numbers on it either so I don't know what it is other than that it is 3-blade aluminum.

The hull is a fairly light (700 lbs) 15ft v-hull skiff.

Can somebody point me at what I might need?

 

[Sea Rider]

Take current prop to a prop shop and have it measured, once knowing diam/pitch, install an induction Hardline Hour/tach on tiller, go for a wot test run you alone while lightly loaded on flat calm no wind water cond. check achieved max wot revs, compared them to factory wot range for that 40 OB. Will know if inside safe rpm working parameters, best is to run around or at max wot revs. Can play with pitches to suit best your boating needs..

Happy Boating

 

[g1vetter]

There should be a prop shop here in Jax somewhere.

 

[Sea Rider]

Check if info is stamped on prop body..

Happy Boating

 

[steelespike]

Your model number may appear on a freeze plug on the power head.
Do a lightly loaded wot test run.get us the present prop size near the base of the blades or under the prop nut.
Get us the rpm and gps speed.

 

[g1vetter]

I know there used to be several Prop Shops around Jax but was told today they all went out of business. Too bad.
I did find one helpful Marine Mechanic that helped me find the prop info on the hub. It is a Michigan 012038, 12 1/4 x 15

Wish he had one, I would have been happy to give him some business.

 

[Scott Danforth]

General Propeller here in Bradenton does great work.

 

[Sea Rider]

You should not replace any given same prop with a new one prior taching delivered prop, then will know if replacing by same one or go for less pitch if need to rev around max wot revs which is the way to go and that's if you want to take all the horses out of that 40 OB..

Happy Boating

 

[flyingscott]

Take the prop off and where the nut came off look at the hub most props from OMC have the pitch and diameter there

 

[g1vetter]

Ordered a tach. I'll install and see what she is doing.

 

[Sea Rider]

You'll love to play with tach rpm and pitches...post wot rpm with factory delivered prop.

Happy Boating

 

[g1vetter]

I borrowed and installed an aluminum 11 3/4 x 17 prop. The boat ran 27mph at 5100 rpm. Fully loaded boat, though. Full Tank (12 gal), 3 people, and fishing tackle.
Thoughts?

 

[Sea Rider]

With 17 pitch, was it easy for boat to plane, needed to go full throttle to maintain nice plane ?

What's the max wot range of that OB ? If it's 5500 rpm one less pitch will put revs around max. Keep in mind that maximizing a prop for family/friends boating is not same as proping for boating solo or very lightly loaded. If yo go for full wot range with different prop while heavily loaded, that OB will overrev when boating solo or lightly loaded will need to have both eyes on tach...Do you plan going boating with 3 up, and heavily loaded on a regular basis ?

Happy Boating

 

[fhhuber]

I borrowed and installed an aluminum 11 3/4 x 17 prop. The boat ran 27mph at 5100 rpm. Fully loaded boat, though. Full Tank (12 gal), 3 people, and fishing tackle.
Thoughts?

sounds pretty decent for a 40 hp

Pretty heavily loaded boat and still getting up into the power band for the motor.
Take a quick run light loaded (dump all the extra people and fishing gear) and my bet is it approaches red line rpm which would indicate you are right where you need to be.

 

[g1vetter]

Normally will be just 2 and I probably wouldn't keep more than 6 gallons of gas in the tank. Seems like I'm close.