Changing to a 4 blade

ILOVEBEER · Sep 9, 2006

Hey guys, I have a 19P SS 3 blade prop and I want to change it to a 4 blade prop. If I am happy with the WOT RPM, do I keep the same pitch or do I have to step up or down? Thanks

Silvertip · Sep 9, 2006

Re: Changing to a 4 blade

You should be asking if it is necessary to go to a four blade. What issue are you trying to resolve? If you are looking for higher performance -- the answer may not be a four blade. If you are looking for hole-shot, a four blade will help. Several reasons to go to a four blade and several reasons why its not necessary. However, since you asked, to keep the same WOT rpm you would decrease pitch.

ILOVEBEER · Sep 9, 2006

Re: Changing to a 4 blade

I already posted my problems in another post (I couldn't find it) and the concensus is a 4 blade prop. So if I have a 19P now, I should drop to an 18P or 17P? I am currently turning 4920 rpm (rec is 4400-4800) so I could stand to lose a hundred or so RPM, so I am wondering if I should stay with a 19P. How much will the WOT RPM drop if I stay with a 19P?

Thanks

walleyehed · Sep 9, 2006

Re: Changing to a 4 blade

About 200...
But,...is your WOT RPM of 4920 with a Normal load on board?

ILOVEBEER · Sep 9, 2006

Re: Changing to a 4 blade

Thanks Kenny. Yeah, it's close to normal load. When I tested it I had 3 people, wakeboard gear and a cooler full of ice. So maybe I should stay with a 19P. Sounds like it will bring down the RPM and keep the top end. What do you think?

Now how about recommending a good prop. I would like a good holeshot, little venting, and good bite but I don't want to lose too much top end. Is that even possible?

1998 Sea Ray 190 4.3L EFI/ alpha 1

Thanks for all the help guys!

walleyehed · Sep 9, 2006

Re: Changing to a 4 blade

Gonna be tough to keep all the top-end, but give me a refresher on the boat type and the prefered performance you want, and I think we can nail one down for ya.
Also, how does the boat perform with the 19P 3-bld? I need to know if the boat is heavy in the rear, etc...how does it act coming out of the hole?
Sorry for the extra work, but there are a few "Key" elements that will lead us to one choice over another.

walleyehed · Sep 9, 2006

Re: Changing to a 4 blade

Gonna be tough to keep all the top-end, but give me a refresher on the boat type and the prefered performance you want, and I think we can nail one down for ya.
Also, how does the boat perform with the 19P 3-bld? I need to know if the boat is heavy in the rear, etc...how does it act coming out of the hole?
Sorry for the extra work, but there are a few "Key" elements that will lead us to one choice over another.

ILOVEBEER · Sep 10, 2006

Re: Changing to a 4 blade

No Problem Kenny, I really appreciate all your help.

The boat is a 1998 Sea Ray 190 bow rider with a 4.3L EFI and a Alpha 1 drive (1.81).

If I have 4 people in the boat (none in the bow) the boat goes WAY bow high and struggles to get on plane. If I put someone in the bow, the boat will get on plane better, but the prop will vent if I even trim up a little bit. If I am pulling a boarder, the prop vents easily if I trim up to clean out the wake. It tops out at 46.7 MPH (GPS) at 4920 RPM with 3 people and gear.

My goal by switching props is to achieve a better hole shot when the boat is loaded or when pulling a boarder, and to reduce the ventilation so I can trim up to clean up the wake. I would like to have all this without giving up too much top end. Am I dreaming?

Did I miss anything?

Thanks again

-Warren

Tail_Gunner · Sep 11, 2006

Re: Changing to a 4 blade

Currently im in a 18.6' 2800lb boat with the same engine. The mfg put a 23p prop on the boat originally however there is now a 19 on the boat. Out of the hole i could pull a tree out, however @ wot or trimming up i too have venting issue's and yet the boat greatly increases it's speed so i have gone to a 20P 4 blade ( i would have prefered a 21) The prop will arrive today or tomorrow and i will post my result's.

You might want to look @ some smart tab's, they really do generate a lot of lift, but if your boat preform's like this Welcraft id say a 19 is far to little prop. I had a few costly error's during a restroation or i now would have a 22p-23p enertia on it's tail..

ILOVEBEER · Sep 12, 2006

Re: Changing to a 4 blade

Thanks Gunner. I think the boat originally came with a 21P but it was swapped out for the 19P SS. For what reason, I don't know. I don't know how the boat will perform with more prop, but because I am already having hole shot issues with the 19P, I am hesitant to increase the pitch. I think the 4 blade is the answer. From what I have been reading, a 18-19P should be about right. BTW, what model prop did you buy?

Hey kenny, have you come up with anything yet?

Thanks!

walleyehed · Sep 12, 2006

Re: Changing to a 4 blade

Haven't forgot ya yet!
One more clue I need is the Model of prop you have....I think you said before that it was a MWC?
If it is, let's make sure of "what" model we have..ie, a Rapture, michigan match, or even the P/N under the nut.
Let's make sure we don't have a bow-lifter when we may need a stern-lifter....

Tail_Gunner · Sep 12, 2006

Re: Changing to a 4 blade

8) I wouldn't begin to second guess walleyehed on my best day, i recieved today and will run it tommorw moring and will post the result's

walleyehed · Sep 12, 2006

Re: Changing to a 4 blade

Something else I just caught is the numbers you list....If we have a known GPS of 46.7 with what we believe is a 19P.... we have a serious tachometer issue.
Your numbers equate to about 5% slip..I don't feel that's right. If I use 10% (relatively good/efficient number) I come up with over 5100RPM...and with that being said, normally when we see these numbers, RPM-wise, the hole-shot is "usually" decent.
It's going to be very important that we know what prop that 19P is, and it is very important we get an accurate RPM with a known prop.
I hate to steer you to a prop based on in-accurate figures and get us both in trouble.
Sorry I didn't catch this sooner....

Dhadley · Sep 13, 2006

Re: Changing to a 4 blade

Good catch Kenny. That's probably why the holeshot is still that good with that much load.

I'd get rid of the cooler full of ice though. No sense dragging around a cooler of ice.........unless..............

Tail_Gunner · Sep 13, 2006

Re: Changing to a 4 blade

ILOVEBEER said:
Thanks Gunner. I think the boat originally came with a 21P but it was swapped out for the 19P SS. For what reason, I don't know. I don't know how the boat will perform with more prop, but because I am already having hole shot issues with the 19P, I am hesitant to increase the pitch. I think the 4 blade is the answer. From what I have been reading, a 18-19P should be about right. BTW, what model prop did you buy?

Hey kenny, have you come up with anything yet?

Thanks!

I picked up a Stilletto Bay Pro ll 20p 4blade and i am very happy with it's preformance. Man this prop is a real lifter the results are as follow's

The wake has shifted about 1 1/2' to the back of the boat
It also has changed from a very uniform wake about 8" tall to a very frothy atomized wake and come's up directly behind not along side of the boat.
You can actually see the imprint of the vee in the water and there's very litte wake at all, the boat's way on top of the water.
As to speed the speedo posted 55 mph that's a 5 mph gain, the rev limiter never once kicked in and i believer i experinced chine walk ( damm hull bounced left to right until i cut speed)

It now cruise's @ 40 with far less effort (general feeling) all in all i am very statisfied.

But it did not improve my hole shot...............at least i couldn't detect any stronger jump ohh and no cavitation takes place anymore and the low frequency grumble i used to have @ wot is now gone also......

Dhadley · Sep 13, 2006

Re: Changing to a 4 blade

When you raise the motor a bit it should eliminate most of the chine walk and improve holeshot. Ain't it amazing what a prop with bite can do?

Tail_Gunner · Sep 13, 2006

Re: Changing to a 4 blade

Yes it is, i put some smart tab's on a 17' Starcraft and they did lift the boat in the same manner and lessened the wake along with a better hole shot. However the combination of increased speed, smoother midrange, the chine walking and watching that prop lift the boat and atomize the wake really was pretty cool.

Unfortunatley im running a i/o and cannot raise my motor or trim her out anymore,,,,,,,,,,,,but then i never tried to trim it out when it started wobbling , i had never experienced that before and was concentrating on the effect it had on the boat.

Yes it was pretty cool to watch and feel it work, what wil be really intresting or satisfying is how it reacts under a heavy chop........im hoping it smooth's the whole affair out. I was able to find a a couple of large boat's and run over there (opps that run on top) of there wake but it was so fast or breif nothing could be determined.

ILOVEBEER · Sep 14, 2006

Re: Changing to a 4 blade

Thanks guys.

My current prop is a 19P Merc Vengeance.

...as to the tach issue, I have accepted that my tach isn't accurate, so the reading I used above was from a timing light that I took to the lake with me. I didn't think it would be off. The speed however, is definate. I guess I could try another tach but that is all I have for now.

walleyehed · Sep 14, 2006

Re: Changing to a 4 blade

Any chance that prop has been repaired or worked...or even worn substantially?

ILOVEBEER · Sep 14, 2006

Re: Changing to a 4 blade

I don't think so, it looks brand new. No dings, dents, or even any marks for that matter. All edges look brand new.

Changing to a 4 blade

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