help with selecting prop for Johnson 30hp...

super_snappin

Recruit
Joined
Jun 15, 2011
Messages
2
Hello all,

First time poster since buying my first boat this spring. I've been coming here to get up to speed on maintenance and tips on tuning the boat and really appreciate all the information people have posted. I'm currently trying to select a better prop as I believe the current one is over reving. I currently have a 4-blade 10.5"x12p prop on it which turns at 6100rpm at WOT. Since I am on a rather small lake and use the boat primarily for fishing, I don't care much for top speed but would like the RPMs to come down to the recommended range of 5200-5800. I've been considering a 4-blade 10"x14p or 10"x15p but would also consider a 3-blade as well. Would anyone be able to recommend a good aluminum prop to suit this setup?

Here are the following specs of my boat to the best of my knowledge:

2) Current prop manufacturer, model, aluminum or stainless as a minimum.
4 blade aluminum (sorry can't figure out the manufacturer)

3) Current prop diameter and pitch (required).
10 1/2" x 12

4) Wide open throttle RPM and speed with an average load (very helpful)
6100 rpm at WOT. 20mph with 2 people, dog and fishing gear.

5) Engine/drive make, model, year, and HP
Johnson 30hp, J30ELERM, 1994

6) Boat make model, year, length and weight
2000 Sylvan, Super Snapper, 14.2ft, approx 400lbs

I would appreciate any help. Thank you all for reading this.
JD
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: help with selecting prop for Johnson 30hp...

If my math is right I think your tach is wrong ,your speed is wrong or or you have an amazing amount of slip. My figures say, allowing for 10% slip, you should be running about 31 mph.
@ 6100 rpm.I think it is the tach it may be on the wrong setting.
Reduce the rpm by 30% would put you at about 21 mph allowing 10% slip.
Once you have the tach settled it would be good to get the max rpm and speed at wot.
both loaded and empty.
 

super_snappin

Recruit
Joined
Jun 15, 2011
Messages
2
Re: help with selecting prop for Johnson 30hp...

Thank you for your help. I will be back on the water this weekend and will check the tach and the speedometer to see if they are working properly.
 
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