Is this the right prop/speed for this boat?

[olsenk514]

Hi all...i've been reading through this forum alot and there's tons of good information. I recently purchased a bass tracker with a 50hp force and I was wondering if the speed i'm getting seems good enough for the setup...

1) Performance issue you are trying to correct.
trying to maximize the efficiency of the prop...more concerned with top- end speed than hole-shots
2) Current prop manufacturer, model, aluminum or stainless and as a minimum.
I believe it's a quicksilver prop...no manuf. stamped on it. it is aluminum
3) Current prop diameter and pitch (required).
Measured diameter is 10 3/8. Putch is stamped 11 1/2
4) Wide open throttle RPM and speed with an average load (very helpful)
Not sure how accurate the tach is, but it's around 5300. Seloc specs are 4500-5500
5) Engine/drive make, model, year, and HP
1988 Force 50HP serial 507F88D..gear ratio is 1.62:1
6) Boat make model, year, length and weight
1994 Bass tracker tx-17. 17' aluminum hull...weight is estimated at around 1200 lbs.

I tried the prop slip and speed calculator at go-fast.com and it says my speed should be in the high 30's. Am I getting the speed I should, or is something wrong

Thanks
Kevin

 

[steelespike]

Re: Is this the right prop/speed for this boat?

I didn't see your speed listed.? The TX 17 came with a 40 in 94.
Is your the 40 or a 50?
weight with motor is 1440.Is it a Jon boat style?

 

[olsenk514]

Re: Is this the right prop/speed for this boat?

Sorry...top speed right now with just me in the boat is around 24 mph.

The motor is not the original...it's a force 50hp. The motor weight is about 150 lbs. It doesn't have power trim/tilt, but i've tried each hole setting and have found the highest is 24mph.

And yes...it is "jon style," not a v-hull

 

[steelespike]

Re: Is this the right prop/speed for this boat?

It would appear your rpm is pretty close Speed seems low though the 50 Force is not known for its speed.Is your speed by GPS?
Your antivent(cavitation) plate just above the prop even with the bottom of the boat is considered a starting point for height.You could try raising the motor a hole at a time to a point just before venting(cavitation)becomes a problem.Under ideal conditions you might gain a couple of mph.
Check that the throttle opens all the way,motor in excellent tune, prop is in excellent condition.

 

[olsenk514]

Re: Is this the right prop/speed for this boat?

Yes...speed is by gps. I have the tilt pin in the 2nd hole from the highest. On the highest hole, I do get problems with ventilation.

The prop is a little nicked up. I'm probably going to get a new prop this week sometime...should I stick with the 11 1/2 or go up to a 12 1/2 or 13? In the calculators i've tried the result ranged from 11 1/2 to 13 1/2

Also, do you have any idea what speed I should be reaching for? I know these force motors are over-rated, but i'm not sure by how much...

Thanks

 

[hwsiii]

Re: Is this the right prop/speed for this boat?

Olsen, I don't know what calculator you used, but your boat should do about 31 to 33 MPH at top speed. Your prop slip is right at 33% right now and that is your problem. Sine you do not have power trim, that also stops you from attaining your maximum speed, because you can't adjust the motor to the perfect sweet spot that it wants.
I would recommend you raise the motor as high as you can on the transom, with the motor tilted out to the second or third pin setting for tilt until you find the speed to come up to at least 27 MPH. I also would try and have the prop shop put about .5" of cup on the trailing edge to cut down your prop slip. You really would be better off with a 4 blade prop, but I can't find one for your motor.
If you try a 12.5" pitch prop in the same make and model of prop you have now you will lose right at 400 RPM and even have more prop slip than you do now as well as lose hole shot and acceleration.

Prop Pitch and Speed

Prop Slip

H

 

[olsenk514]

Re: Is this the right prop/speed for this boat?

thanks hwsiii...

I'll try moving the motor up a little bit on the transom this week. Right now, the cavitation plate is about an inch or 2 below the bottom of the boat.

They have a limited number of props for this dinosaur motor (i couldn't find any 4-blades either), so I may look for a new 3 blade aluminum. Would a 12.5 give me any more top speed or no? Also...the prop on there now may very well be the original prop...the powder coating is almost completely gone and the aluminum almost looks pitted.

any round-about $$ for cupping the new prop?

Thanks

 

[hwsiii]

Re: Is this the right prop/speed for this boat?

In my opinion a 12.5"pitch is too much, and what you really need is more cup on the trailing edge to cut your prop slip down, and I don't know where you live but I wouldn't pay over $ 40 for it.


H