Prop & Slip question 130hp Johnson?

[Hairygary]

I have a 2000 Four Winns 180 Horizon F/S with a 130hp johnson. I have the stock prop on it which is a 3 blade aluminum 14 1/2 x 19. At WOT I am currently getting 42 MPH at 5200 RPM, using both dash gauges, not GPS. I believe the gear ratio to be 2.25:1 from what i found on the internet

I have two questions?

1. When i put the above numbers in a slip calculator it says that I have ZERO slip. I know this is wrong, could my tach be wrong. When I put in 5800 rpm in the slip calc. it says about 10% slip, which I believe to be more realistic.

2. I like to do wakeboarding and tubing and I was having trouble holding plane at low speeds (20 MPH) and was coming off plane in high speed turns while tubing, so I just purchased a used OMC Renegad offshore prop in 14 1/4 by 19. Do you think this prop will help?

 

[rndn]

Re: Prop & Slip question 130hp Johnson?

Welcome to the forum!!
You can't trust the speed numbers from the dash mounted speedometer as they are almost always wrong. You should have the rpm's closer to the max which I believe is 6000rpm's at wide open throttle (WOT). You should consider trying a 17" pitched prop as it should raise your rpm's by around 400.
To assist in holding plane at lower speeds you may want to try smart tabs. A four blade prop will also help but the smart tabs are the way to go.

 

[Hairygary]

Re: Prop & Slip question 130hp Johnson?

Thanks for the reply. If the speedo is off 2 mph per hour and I put the stats in a slip calculator It still only shows about 4 % slip, which still seems to low.

I just ordered a clamp on digital tach, as I am convinced the tach is off, but I shall see.

I now have three props Im gonna do a test with all three next week. 14 1/2 x 19 aluminum another 14 1/2 x 19 that i had repitched to 18 and the new Renegado offshore. If the offshore doesnt give me enough RPM's I guess I will have to have it repitched to a 18, since I already have too much money in it to buy a 17P now.

 

[rndn]

Re: Prop & Slip question 130hp Johnson?

I'm sure your speedo is off by more than 2mph. On my boat the speedo is off by 8 mph at top end. That's the nature of these speedo's.

 

[Hairygary]

Re: Prop & Slip question 130hp Johnson?

alright, you got me a little depressed thinking my boat is only going like 35MPH as opposed to 42. I need to find friend with a GPS, or purchase a cheap one so I can find out.

 

[Hoss 350]

Re: Prop & Slip question 130hp Johnson?

I really do not know if this is germaine to this converstation, but I have a similar boat, a 1996 four winns horizon 170, with the Johnson 130 OB on it, and my prop is a 14 1/4 21 pitch, and here are my numbers:

WOT RPM - 5250 to 5300

Top Speed - 43 mph (taken off of a pinwheel-type on my fish/depth finder, which i think is pretty accurate)

If that is the case, I have about 9% slip on this prop.

Like I said, dunno if this helps you at all, just figured it would be helpful to have a similar boat's numbers for your analysis...

 

[Hairygary]

Re: Prop & Slip question 130hp Johnson?

Hoss, thanks for your input. This just goes to show if you are getting 43 out of your 170 with a 21P prop, there is no way I could be getting 42 out of my 130 with a 19P prop. I understand why you have the 21P as i think my boat weighs about 300 lbs. more and the 2000 170 model is about 6" narrower and 1'6" shorter.

If you dont mind me askin, how close is your dash speedo compared to your fishfinder speedo?

 

[rndn]

Re: Prop & Slip question 130hp Johnson?

HOSS, The suggested rpm's at wide open throttle (WOT) for your motor is 5000 to 6000. Constant running at the 5200 to 5300 range will cause it to die an early death. You should prop it to run closer to 6000 than 5000. Your engine will show it's appreciation by adding years to it's life.

 

[Hoss 350]

Re: Prop & Slip question 130hp Johnson?

Hoss, thanks for your input. This just goes to show if you are getting 43 out of your 170 with a 21P prop, there is no way I could be getting 42 out of my 130 with a 19P prop. I understand why you have the 21P as i think my boat weighs about 300 lbs. more and the 2000 170 model is about 6" narrower and 1'6" shorter.

If you dont mind me askin, how close is your dash speedo compared to your fishfinder speedo?

1-2 mph for the most part. The dash speedo is a "water pressure" kind where the force of the water rushing into the tube tells it how fast it's going. The fish finder has a pinwheel on the back of the transom that spins as water goes by. Dunno which is more exact, but they are pretty close. The dash speedo runs BEHIND the fish finder speedo, BTW. Fish finder showing 43 dash speede shows 41.

 

[Hoss 350]

Re: Prop & Slip question 130hp Johnson?

HOSS, The suggested rpm's at wide open throttle (WOT) for your motor is 5000 to 6000. Constant running at the 5200 to 5300 range will cause it to die an early death. You should prop it to run closer to 6000 than 5000. Your engine will show it's appreciation by adding years to it's life.

Thanks for the input. You helped me on the other post witht he same info. I think I'm going to try my 19 pitch and see what it will do for me.

 

[Hairygary]

Tried the new prop out.

Tried the new prop out.

Ok, I took my boat out for the first time this year and tried out my new OMC Renegado offshore 14 1/4 x 19 4 blade prop. I got 42 MPH (dash speedo) at wot of 5200 rpm. I am happy with the performance of this prop as these are the same exact stats I got from my aluminum 14 1/2 x 19 3 blade prop, except that it planed out alot quicker (about 20 MPH).

I know that I am still lugging this engine a little as my max rpm range is 5000 - 6000, and I am thinking of getting my new OMC renegade repitched to a 18 pitch. It is bad to get a stainless prop repitched? I understand I will only get about 200 more rpms by dropping one pitch, but that will put me a little closer to the rated of hp of 130 @ 5500 rpms. I hate to drop all the way down to a 17 pitch and loose some speed, plus I dont think I can drop down 2 pitches on a stainless prop from what I heard.

 

[Dhadley]

Re: Tried the new prop out.

Re: Tried the new prop out.

You are absolutely correct. Going to a smaller pitch will most likely decrease efficiency. Gain rpm with the current prop and play with the set up.

Repitching any prop to a lower "pitch" only reduces bite or thrust. All that does is allow the prop to slip more.