Prop Question

[kax2000]

How much performance/speed/rpm loss is the damage on this prop causing?
I am currently getting 4200 rpm. Which prop do I buy?

Currently 1995 50hp Johnson / 5500 max rpm / 11-3/4 x 17 / 16 ? ft. bass boat @ 2240 lbs. including trailer

 

[Johny25]

Re: Prop Question

I don't think you are losing 1300rpm due to the prop being a little damaged. Maybe a few hundred, but it is hard to say. Theoretically you are looking to gain another 1100-1300rpm but going down 6 pitches to an 11 pitch does not seem correct although you are pushing a lot of weight with that 50hp. I would guess that a 13 would serve you pretty well, but it is just a guess?

Looks like you could take a grinder or a file to that prop and get a lot of those burrs off. And you may be able to lightly hammer some of those bends out also. Then see what your RPM is and we can get a better idea what you got going there : )

 

[Johny25]

Re: Prop Question

Correction: 2240lbs including trailer? What does it weigh without the trailer? That is assuming you unhook it from the trailer while fishing

 

[steelespike]

Re: Prop Question

If you get us the info requested in "read this first" at the top of the prop forum it will help.
No doubt your prop is causing performance issues.A bass boat is intended to go fast so a 15 or 17 " prop should do well.

 

[kax2000]

Re: Prop Question

I installed new 12.5 x 13 prop with no improvement in RPM?s at WOT.

 

[Johny25]

Re: Prop Question

Something is not right then...... You dropped 4 pitch and the RPM is still the same?

 

[kax2000]

Re: Prop Question

Something is not right then...... You dropped 4 pitch and the RPM is still the same?

Yes dropped 4 pitch and increased from 11 3/4 to 12 1/2 diameter.

 

[steelespike]

Re: Prop Question

We still need you to get us the wot rpm and speed by gps.And remind us of the prop size.
Speed is easy with a gps. Some cells have a gps app.
No change in rpm I would suspect the tach.
Rpm alone doesn't mean much. It only indicates the rpm.If we have the prop and speed we
can usually figure out if there is a tach or motor problem.
For instance your at 4200 rpm and need to make up 1200. That would require up to a 6" reduction in pitch.
That would put the prop at about 11" The size you would use on a very hard to push pontoon.
With your rpm and speed we can see if its a motor problem or else where.

 

[kax2000]

Re: Prop Question

We still need you to get us the wot rpm and speed by gps.And remind us of the prop size.
Speed is easy with a gps. Some cells have a gps app.
No change in rpm I would suspect the tach.
Rpm alone doesn't mean much. It only indicates the rpm.If we have the prop and speed we
can usually figure out if there is a tach or motor problem.
For instance your at 4200 rpm and need to make up 1200. That would require up to a 6" reduction in pitch.
That would put the prop at about 11" The size you would use on a very hard to push pontoon.
With your rpm and speed we can see if its a motor problem or else where.

1) Performance issue you are trying to correct.
Boat is slow
2) Current prop manufacturer, model, aluminum or stainless as a minimum.
First prop: don?t know manufacturer, don?t know the model #, aluminum.
Second prop: QL, A3r, aluminum.
3) Current prop diameter and pitch.
First prop: 11-3/4 x 17
Second prop: 12.5 X 13
4) Wide open throttle RPM and speed with an average load.
First prop: 4100 to 4200 at 11 mph (gps)
Second prop: 4100 to 4200 at 12 mph (gps)
5) Engine/drive make, model, year, and HP
Johnson, J50TLEOD, 1995, 50HP
6) Boat make model, year, length and weight
Ebbtide 166 STE, 1987, 16.5?, 2240 lbs. including trailer

2 carb rebuild kits w/ floats on the way from iboats.