Viper Prop

[jkimball]

Wanted to see if anyone has any experience with Viper Stainless props.

I have a '99 FW Horizon 170 with a Johnson 115. Recently I changed props from the original beat up 19p aluminum that came with the boat to an OMC 17p stainless and gained ~500 rpms (went from 4,900 to 5,400-5,500 WOT) and about 4-5 MPH top end (went from 38-43/44 MPH) all while having an awesome hole shot.

So, I got to thinking that since I saw such an improvement with a 17p stainless, I wonder what kind of results I would have with going back to the OEM pitch size of 19p but in stainless since it has less flex and generally nets more rpms than a comparable aluminum.

I ran across a good deal on a 19p OMC Viper Stainless, and got it for $79 shipped. I got the prop today and it's in great shape, hub looks good and no nicks or dents on the leading edges or tips. So for $79... not bad!

I just want to see what the general consensus is. I've heard good and bad of these props. I know I'll likely lose some hole shot and some rpms WOT, but I should still be in the "safe zone" on WOT rpms as the manufacturer states 4,500-5,500 is acceptable.

All things consistent, since I noticed a top speed increase from going down 2" of pitch switching to stainless, is it reasonable to assume that I'll notice an even greater increase on top speed returning to a 19p stainless? Or will bringing the rpms back down to around ~5,000 cancel this out and I'll break even with what I'm netting on the 17" wheel?

 

[steelespike]

Re: Viper Prop

For one reason or another your numbers don't add up. 38 at 4900 with the 19" prop indicates a fairly reasonable 13% slip.
45 at 5500 with the 17" prop isn't possible. It requires negative slip,not possible.
I suspect your speedometer is not accurate. Also its possible the tach is suspect.
If we assume the 5500 is accurate and use a reasonable 10% slip we get 39.8 mph.with the 17".
If we use 5000 with the 19" at 10% we get 40.5. esentially the same speed.
Usually the tach and/or the speedo are the culprit when the numbers don't add up
though setup can be at fault as well.
If you use a gps it will eliminate the the speed question.
While a ss prop can improve overall performance;
You need to take into consideration Your beat up aluminum as not up to par.
Rule of thumb a 2" decrease in pitch will add "about" 400 rpm and no doubt
have vastly improved hole shot.
I think the 600 rpm increase is probably partially the result of the tired prop.
You have the 19 and it should do well.
Set her up and lets see how it goes.

 

[jkimball]

Re: Viper Prop

The speed is by GPS. As I said in my post, I have gotten it up to 44 mph, only once though.
On average, my top speed is 42-43 fully loaded at 5,400-5,500 rpms.

My pitot driven speedo is crap and bounces all over the place so I use GPS all the time.

 

[steelespike]

Re: Viper Prop

I see where I got the 45 You mentioned gaining 4-5mph I read 45 mph.
Still can't make 43 at 5400 thats 1% slip,not possible.
So we know speed is accurate . Speed at about 5400 10% slip is about 39.1.
19" at 5000 @ 10%=40.5. This is assuming 2.00 gear ratio.
So it appears the tach is reading low.
It appears your at about 5900 to make 43 with 10% slip.
Keep in mind you went from a tired aluminum prop to new ss prop
and reduced pitch so excellent performance isn't too surprising.
Are we dealing with any current, tide or wind?

 

[mpsyamaha]

Re: Viper Prop

interested to see the results with the 19p viper prop. With the suspect tach, it seems the rpms are higher, steelespike knows his stuff. The 19 might be a better prop for you and pick up a few mph, but if this is so, keeping the 17p for heavier loads, or times when you need a fast holeshot would be nice.

 

[jkimball]

Re: Viper Prop

Sorry for being checked out guys, holidays and family have kept me away from the forum. But I put the prop on and the results were, with a full load (4 adults, 2 kids and a 26 gal tank of gas) Top speed was sustained 41 MPH at 5k RPMS. Hole shot was still "ok" but obviously not a stump puller like with the 17p.
When I unloaded the boat a little (2 adults, 1/2 tank of gas) top speed fluctuated 44-45 MPH at about 5150 RPMS. Using the Mercury prop slip calculator, it puts my slip at around 4%

As for the slip with the 17p when I use the calculator it comes out to somewhere between 3-5% slip. The top speed with the 17p has seen 43-44 MPH but I would feel comfortable saying the avg is 42.

 

[phillnjack2]

Re: Viper Prop

I love it when impossible speeds are got with specs that don't add up.

5500 rpm with 17 pitch on a 2to 1 gearbox is maximum possible 44.27, that would be with no boat just the engine !!!!
now if you have a super doper ultra efficient hull and a lightweight driver you could get a slip of around 5%.
this then brings the speed down and would be fantastic to get 42mph.

now as soon as you start talking about 4 people youl be in the region of 15 to 20% if its realy good so 35 to 37mph at these figures.

now if the prop is cupped, then it will add 1 inch of pitch so slap on another 1mph to these figures.

with a 19 pitch that is also cupped at 5500 rpm youl be very very lucky to see 47mph with very lightweight boat and fantastic .

top speed with 17 pitch prop at 42mph need to have 5500rpms at 55 slip... youl need some very very goodset up to achieve this.
most race boats only achive this when made of lightweight materials and many years of race development.
.

 

[jkimball]

Re: Viper Prop

I love it when impossible speeds are got with specs that don't add up.

Thank you for your criticism oh high and mighty captain of the internet marina...:hail:

I appreciate your enthusiasm in attacking what was posted but please don't try to come in and essentially say that I'm blowing smoke... I have no need or desire to try to impress anyone with fabricated numbers. What benefit is there in trying to show off on an internet forum?

I never denied that my Tach may be off as steelespike stated, I was simply stating the numbers and stats that I can personally attest to. Whether my tach is off or not, Don't know... personally don't care... it says 5.5k so I simply relayed what it read. The rest of the stats and specs are definitely factual and accurate whether they "add up" or not.

So unless you have something truly beneficial to add to this thread, don't come in and chime in with unneeded criticism and try to attack another poster's credibility.

Good Day Sir.

 

[jestor68]

Re: Viper Prop

Are you guys forgetting to add the inch of pitch (for cupping) in your charts and graphs ?

The performance numbers make more sense that way.

 

[phillnjack2]

Re: Viper Prop

I am so glad you think of me as being so high and mighty.
But its just your lack of knowledge on prop / speed calculations that make me look so good. not my fault !!!!!!

Now there is no point in putting down any figures at all if they are going to be so far out. again not my fault !!!!
no point even asking a question if the facts are so incorrect.
even a fool with a simple calculator could see the facts given are an impossibility.

to come on here and ask for help then give such figures and then have the cheek to complain is what I would call just asking for trouble.

I suggest you go get a checked/calibrated tacho, then take the boat on a measured distance then come back with its
true mph and rpm readings and you might have half a chance of getting a realistic answer and possible bit of knowledge as
to what may help you in your quest for a nice all round setup.
plenty of folk on here will of seen your first post and just not bothered to read any more.

just to add.
OMC have never put the 115hp v4 2 stroke engine as wide open throttle range to be in the 4,500 to 5500 rpm bracket.
its always been 5,000 to 5,500 rpm.
at under 5,000 you are not in the power band and would be lugging /straining the engine and wearing it out faster.

and four winns claim that the boat alone weighs 1790 pounds (811 kilo's).

with a strong engine and good prop you will end up with a 42mph boat that should pull up a skier.

goodbye.

 

[zenwriter]

Re: Viper Prop

You are wrong about the operating range of the OMC 115 2 cycle. I'm looking at the service manual right now, P/N 787070, page 1-8, and it says "Full Throttle Operating Range: 4500 to 5500 RPM"

 

[Georgesalmon]

Re: Viper Prop

Merry Christmas,,,,,,,,,

 

[steelespike]

Re: Viper Prop

Early 115s were 4500-5500 hp developed at 5000. present day 2000? 0n are 5500-6000. hp developed at 5750.
Apparently there is a pontoon version with a 2.44 ratio, a 20" has a 2.00 and the 25" 2.25. ratio.
These could cause some confusion as time goes by.

 

[zenwriter]

Re: Viper Prop

Maybe the 5500-6000 RPM spec started in 2001, as the year 2000 service manual says 4500-5500.

 

[steelespike]

Re: Viper Prop

Im thinking ,now, that 5500-6000 probably arrived with the introduction of the Etec.