Walleyed...Propco says a little larger replacement diameter Is OK? Yes/No?

[harrisg]

I have a Volvo Penta AQ125A motor and 270 outdrive. My current WOT is about 4400rpm. Specs say 4400 - 4800. <br /><br />I am running a 14x19 VP 814633. Propco shows their replacement as a 14 1/2 x 19. Since I'm so close to the low end of WOT, will the extra 1/2" of diameter make any difference? Propco says it will not make any difference. Are they right?<br /><br />Another possibility is to go to their 14 3/4 x 17. Would this be a better choice since I'm at the low end of WOT now?

 

[shep70057]

Re: Walleyed...Propco says a little larger replacement diameter Is OK? Yes/No?

I can't speak of any other boat/motor combinations but I've already experienced that different diameter props will affect the RPM range on a motor. In recent past I've used an 18P 3 blade 14.25" diameter prop (suzuki)... after getting and running a mirage plus prop which was 15.5" diameter with 17P, my rpm's dropped by 400. Some say that the prop was pitchd up.... it was then brought to a very reputable prop doc in south louisiana who ensured it was a 17p. Why did it go down in rpm's, I can't say. Some will say that it's a different profile (different manufacturers rate their props differently) and you could tell some differences. From what I've learned through trial and error, every 1/4" or so of diameter will equate to 75 or so rpm's. To say that 1/2" will not affect your motor..... can't really say. It's whether or not you are willing to pay for that experience. Since you are at the bottom end of your recommended max range, I would suggest to drop down in pitch.

 

[Silvertip]

Re: Walleyed...Propco says a little larger replacement diameter Is OK? Yes/No?

Switching from one 19 inch pitch prop to another will not likely solve your RPM problem. The 17 pitch would.

 

[mjbrueck]

Re: Walleyed...Propco says a little larger replacement diameter Is OK? Yes/No?

More diameter generally means more prop efficiency. If you're running a more efficient prop at the same pitch, you'll drop your rpms further. I'd go for the 14 3/4 x 17, especially since you're already at the lower range of WOT rpms.

 

[imported_bjs]

Re: Walleyed...Propco says a little larger replacement diameter Is OK? Yes/No?

i always heard that diameter don't make any differnce.guess i was wrong.but think as this way if you put bigger tires on the rear of your truck its supposed to take some of the gear ratio away.true or false.have asked the experts but no can tell me how much gear tires takes away.maybe someone can help us.they say you cant tell any differnce.but it would be the same as different prop.your changing the gear ratio.

 

[notarealone]

Re: Walleyed...Propco says a little larger replacement diameter Is OK? Yes/No?

Stay with what you have. It is always better to be a bit lower than max RPM. IF you did change to a 14x17P you would overrev the motor. Do you have AL or Stainless on now? If you have aluminum, then just go to SS in same size. You will have to adjust the trim a little higher because SS runs better in less water. This will raise you RPM's also. By going to a smaller Pitch or diameter prop you will slow down also. Remember, Pitch=distance traveled in one revolution in inches. Diameter is the amount of bite you need to push the boat forward.

 

[walleyehed]

Re: Walleyed...Propco says a little larger replacement diameter Is OK? Yes/No?

If you have aluminum, then just go to SS in same size. You will have to adjust the trim a little higher because SS runs better in less water. This will raise you RPM's also

Skeeter, I gotta disagree again... the SS in the same pitch is going to lower RPM on an outdrive...SS bites harder requiring less trim for the same ride.<br />If we could raise the sterndrive, I'd say yes, go with the same pitch, but beings we can't, I say 1-2" lower in pitch with SS, maybe 3" less with a high-quality SS.<br />We want to test with a normal load-Not a light load- and we want the RPM at the top of the range...with a normal load.

 

[harrisg]

Re: Walleyed...Propco says a little larger replacement diameter Is OK? Yes/No?

Walleyed... I have an aluminum prop and don't want to spend the extra money for a SS. So back to my original question.<br /><br /> I am running a 14x19 VP 814633. Propco shows their replacement as a 14 1/2 x 19. Since I'm so close to the low end of WOT, will the extra 1/2" of diameter make any difference? Propco says it will not make any difference. Are they right?<br /><br />Another possibility is to go to their 14 3/4 x 17. Would this be a better choice since I'm at the low end of WOT now?

 

[Dunaruna]

Re: Walleyed...Propco says a little larger replacement diameter Is OK? Yes/No?

I doubt you would notice any difference with 1/2" bigger diameter but I believe you are over proped (pitch) for that little 4 banger.<br /><br />What size boat are you pushing?

 

[harrisg]

Re: Walleyed...Propco says a little larger replacement diameter Is OK? Yes/No?

Dunaruna... I'm running a 16 ft 1983 Invader with Volvo Penta AQ125A / 270. It is not the bow rider but has a solid front deck. The reason I'm going with Propco is because it is significantly less than the VP or Michigan wheel for an aluminum prop and has a good reputation. Right now, every buck counts. I'm turning 4400 with the current 14x19 prop. Spec is 4400 to 4800. <br /><br />After reading all this, I think I'll go with the 14 3/4 x 17, which is Propco's direct cross for the Volvo Penta 14x17. Since I'm hearing that the the diameter is not as important as the pitch, and that I should go down in pitch to increase rpm, this now makes sense. Have I got it right?

 

[Dunaruna]

Re: Walleyed...Propco says a little larger replacement diameter Is OK? Yes/No?

Yep. sounds like a plan.<br /><br />Just be aware that before repitching, the motor needs to be running sweet. If the tune is not 100% you won't be making maximum horses which in turn will cause lugging - the very same symptoms as too much pitch.<br /><br />Aldo

 

[stevens]

Re: Walleyed...Propco says a little larger replacement diameter Is OK? Yes/No?

Harrisg - if every buck counts right now, you should consider looking on Ebay. There are some great deals to be had there if you know what you are looking for. No exchanges, though.

 

[walleyehed]

Re: Walleyed...Propco says a little larger replacement diameter Is OK? Yes/No?

The 1/2" might show a bit better hole-shot, but top-end will be the same as will the RPM within 50.<br />Diameter can differ greatly in different blade designs, and even though some pitches are available in differing diameters, that will be a boat weight and engine heigth decision.<br />I do think maybe the 17 would be the way to go with your RPM where it is, and that will leave you the option of having the prop-shop add a bit of cup if needed.<br />adding cup is good, removing is bad.