Mercury prop from 17 to 19p

[1992_Spectrum]

Hello all, I'm new on this forum and would appreciate your help. I currently have a 1992 17'5 Spectrum by Blue Fin. It's an aluminum deep v, dual console. It's equipped with a 1992 Mercury 75hp. It currently has a Turbo SS 13 1/4 x 17 on it right now. It's current WOT is about 5450 rpm and about 32mph top speed. Just recently I went to my local dealer and tried out a Mercury Vengeance SS 13x18. My current WOT with this prop was at 5250rpm and about 35mph top speed.

Now my question is, will going to a 13x19p gain me more top speed? I know I'll lose a couple hundred more rpm's but that doesn't bother me. I really want top speed than anything else. I was told from the dealer that my motor's rev peak is 5500 rpm's.

Thanks for your help folks.

 

[steelespike]

Re: Mercury prop from 17 to 19p

32 @ 5450 is about 15% slip a little high.
35 @ 5250 is about 8% slip good number.I wonder if the Vengeance is a better prop.
Calculator says that a 19" at 5050 will make 35.9 at the same 8%.
As you increase pitch you lose some hole shot and ability to push a load.

 

[1992_Spectrum]

Re: Mercury prop from 17 to 19p

32 @ 5450 is about 15% slip a little high.
35 @ 5250 is about 8% slip good number.I wonder if the Vengeance is a better prop.
Calculator says that a 19" at 5050 will make 35.9 at the same 8%.
As you increase pitch you lose some hole shot and ability to push a load.

My boat is usually about 3 people plus maybe 50 lbs gear. Would a 19p be too big to push this load?

 

[steelespike]

Re: Mercury prop from 17 to 19p

How well does it push with the 17?Are the people 50 lbs or 250 lbs?
I would say the 19"isn't ideal. It will probably push that load but the load will further reduce your rpm.
I don't think the motor will be happy forced to run below 5000 at wot.
You could end up with a boat that is slower than the 17 or 18 props with a load.

 

[1992_Spectrum]

Re: Mercury prop from 17 to 19p

How well does it push with the 17?Are the people 50 lbs or 250 lbs?
I would say the 19"isn't ideal. It will probably push that load but the load will further reduce your rpm.
I don't think the motor will be happy forced to run below 5000 at wot.
You could end up with a boat that is slower than the 17 or 18 props with a load.

Right now with the 17p it has no problem pushing 3 people (about 550 lbs?) and maybe 20-30 lbs gear.

 

[jestor68]

Re: Mercury prop from 17 to 19p

Your 1992 Mercury 75 has a WOT rpm range of 4750-5250. It's gear ratio is 2.30.

The Vengeance 19 should put you right at the motor's rated hp rpm(5000) and gain a couple mph over the Vengeance 18.

 

[steelespike]

Re: Mercury prop from 17 to 19p

Right now with the 17p it has no problem pushing 3 people (about 550 lbs?) and maybe 20-30 lbs gear.

Is your 17" wot rpm and speed with that load?If not what are the results with a load..

 

[steelespike]

Re: Mercury prop from 17 to 19p

Your 1992 Mercury 75 has a WOT rpm range of 4750-5250. It's gear ratio is 2.30.

The Vengeance 19 should put you right at the motor's rated hp rpm(5000) and gain a couple mph over the Vengeance 18.

Don't know if his numbers are with the typical load.
He seemed to really want the best top end over other performance.
If his numbers are with a light load don't you think he might lose speed more severely with a 19" as he adds weight?
So if he runs with 3 people most of the time he may not be at the best top end for his typical operation.
Am I making any sense?

 

[1992_Spectrum]

Re: Mercury prop from 17 to 19p

Is your 17" wot rpm and speed with that load?If not what are the results with a load..

Yes, these numbers are with it loaded. I actually had the chance to gps the speed and it topped out at 34 mph @ 5450 trim up to the max with 3 people (2 adults and a child) and very little gear.

Again this is with my current Turbo 1 SS prop @ 13 1/4 x 17

I'm on the edge on getting another Turbo 1 13 1/4 x 19 as there is a mint condition used one for a decent price.

 

[bikesnboats4ever]

Re: Mercury prop from 17 to 19p

I don't know if you've already gotten a 19p prop or not but I'm looking to trade either a 19p or 21p for a 17p. Mine are both 13 1/4 and stainless. Both are in good condition.