prop shopping

[lorax]

Thanks to the Corp of Engineers strategic location of a unmarked wing dike 18 inches below normal pool and half way across the river, I'm getting a new lower unit and prop.<br /><br />boat is 21ft 5.7 mercruiser. current prop is a SS 13.75(about) X 19<br /><br />I'm wondering if I should make a suttle change since I have to get a new one anyway. The boat seems to have plenty of low end. It'll pull me up (215lb) on a slalom ski pretty easily.<br /><br />It runs out to about 4500 RPM at which point, I think, the rev limiter kicks in.<br /><br />I'm thinking of proping up just a little (20pitch?)to lower the RPMs a little and maybe improve mileage during normal cruising.<br /><br />Any thoughts?

 

[TilliamWe]

Re: prop shopping

What is the manufacturers WOT RPM range for your engine. If it's 4400-4800, don't change to a 20. I also doubt that there is a rev limiter at 4500. That's just where the motor runs out of power to turn the prop you currently have. If for some reason your engine WOT RPM range is something like 4200-4600, then yes, you might get a little something for a change to 20 pitch prop. But it still may take trial and error, as all props are not equal! Think of it a little like Voodoo!

 

[walleyehed]

Re: prop shopping

What kind of RPM do you get with your normal load of people, gear etc..????

 

[lorax]

Re: prop shopping

Tilliam - Max WOT RPM in the book is 4200-4600<br /><br />Walleyehed - The engine runs to about 4500 at WOT<br />it's so consistant about hitting that RPM that I thought it had a rev limiter? It's a '95 merc/chevy 350 4bbl<br /><br />I was hoping to lower the RPMs at cruising speed - (currently about 3000 RPM) down a little and maybe gain a little bow lift.<br /><br />While we're at it, any thoughts on good brands?

 

[lorax]

Re: prop shopping

I'm feeling neglected <br /><br />Seriously,<br />Any comments?<br /><br />While I'm at it . . can anybody explain what the deal is with Mercury props? What's the difference between Quicksilver etc. etc. What lines do they offer? Is there such a thing as a OEM prop? Is an OEM prop better than Pete's Props, Bart's Blades, etc etc.?<br /><br />I used Mercs prop selector and was told the only match was a Vengence 23 pitch. And the predicted top speed was 62MPH. The boat might go that fast if I pushed if off a cliff.<br /><br />Am I way under propped? I'm swinging a 14X19 pitch 3 blade. It's a 3000lb 21 ft V hull with a Cheby 350<br /><br />Your help would be appreciated with any or all of the above questions

 

[walleyehed]

Re: prop shopping

No, you're not way under-propped...that's a perfect example of why I say the Merc prop finder is usually off by quite a bit in-favor of much higher pitch than what reality shows to work best.<br />Quicksilver is an economy version of some of the Merc props, like Lowrance and eagle depth finders...<br />OEM is "Original Equipment Manufacturer", and no, that does not make the prop better in all cases.<br />As for the 4500RPM, is that where it runs with your normal load, or is that with just you in the boat???????

 

[stevens]

Re: prop shopping

To quote from the PropMD.com site:<br /><br />

If your original prop was manufactured by Mercury Marine, the Quicksilver line of propellers is the EXACT SAME PROP however it is sold under the Quicksilver line.<br /><br />For Example:<br />Mercury Mirage = Quicksilver Thunderbolt<br />Mercury Vengeance = Quicksilver Silverado<br />Mercury Laser II = Quicksilver Lightspeed<br />Mercury Vensura = Quicksilver Typhoon<br /><br />

In the Mercury Prop Selector, it is better to input weight rather than length. You want the total displacement weight, not the advertised dry weight. This might give you a more realistic speed. Also, Walleyehed has often said that this prop selector usually gives too high a pitch...<br /><br />OEM props are usually decent but cheap props made by any one of several suppliers, and not necessarily right for your load & use. Walleyehed or Dhadley can tell you which brands are especially good, but I know they have a sweet spot for Turbo, Stiletto and a few others.

 

[walleyehed]

Re: prop shopping

Mercury Laser II = Quicksilver Lightspeed

stevens, I don't doubt the info you have been given, but I have both of these props in the same pitch and the blade shape is different, the degree of Rake is slightly higher on the LaserII, the blade thickness is twice as great on the LaserII at the trailing edge, and tip cup is present on the Laser, that may just barely be seen, if any on the lightspeed.<br />Interesting...<br />I think I will call Merc and see if they would be willing to put their props up against the newest available from several other manufacturers that claim they will out-perform any Merc prop...should be interesting...

 

[stevens]

Re: prop shopping

Hi Walleyehed, you are probably perfectly right as you have hands-on knowledge of this (can't argue with that). I merely quoted from this website (PropMD link). Maybe Merc props evolve over time, and Quicksilver props are earlier versions of the stated Mercury models?<br /><br />That proposed test of yours would be very interesting!

 

[walleyehed]

Re: prop shopping

Merc has agreed to send what I need to test.<br />The gent in charge of prop production and design would not tell me if the quicksilver props mentioned came out of the same mold...<br />I did however, mention the differences I noticed myself, and all he would say is, "well, you'll have to come to your own conclusion then"...<br />Be looking for a new design from Merc called the "INERTIA" not sure of the spelling on that...<br />Supposed to fill the cracks between sterndrive and CC type boats....couldn't get him to cut loose with one of those...said it would be Feb, 06 before they were introduced..

 

[Richard Petersen]

Re: prop shopping

For a comparison 18.5' X 8', V, bow rider, wet 3600#, Chaparral / planing pad. Stock 3 blade 14.25 X 21. 3 seconds on plane & 56 gps. The govenor on a 2002 5,0 L, 220 hp, is 4900 rpm. Mine , me alone, governs every 2-3 seconds on perfect water.

 

[lorax]

Re: prop shopping

Thanks for the responses. That clarifies some things for me.<br />Walleyehead - 4500RPM is with the standard load - me, my spouse, two ankle biters, 3/4 fuel and enough cra..stuff to circumnavigate the world.<br /><br />My favorite prop shop guy has two props he'd like to sell me. One is a Ballistic 14.5 X19 His comment was that the blades are thin on this prop. He says it should perform great but not be as durable as another prop he has which is a Stiletto 14 X 19. Both props have been reconditioned/balanced. He wants $250 for the Ballistic and $350 for the Stiletto. I'm finding new Stilettos on line for $290 so I'm wondering if he's gouging me or if there is some difference in the Stiletto props?

 

[stevens]

Re: prop shopping

Ballistic vs Stiletto??? This is not a trick question, is it?<br /><br />Take the Stiletto, please!!! I've tried both and found the Stiletto to be a much more harmonic prop, and with significantly less ventilation.<br /><br />Why don't you try them both out for yourself? Always fun to learn a bit.<br /><br />You can find Stilettos online for 260-290, or on ebay for 100-150. That he wants 350 is not unexpected given that you are also helping pay for his stock, rent, salary, etc. On the positive side, he will then also exchange it for another pitch if you are not satisified with it.

 

[walleyehed]

Re: prop shopping

Yea, I'll follow stevens on the trick question....To be serious, I have plenty of data that shows a Ballistic performs poorely on "My boat and engine-200Rude", compared to most any SS prop I've ran, and that's a bunch.<br />As stevens said, the Ballistic is very weak strength-wise, and in the 150HP-up class, the Ballistic will bring up the rear.<br />A reworked or repaired advantageII stiletto is worth about 175.00-225.00. They can be bought new for 270-275 in most areas.<br />As for your RPM range, it looks good with the load you have.<br />I "think" your best prop in a 17P is going to be a Turbo I for Mercruiser.<br />If we go with a 19 we are going to see about 100-150 drop in RPM, but the cruise speed will be a bit better. I'd say stay with a stiletto or turbo.

 

[stevens]

Re: prop shopping

A brand new Stiletto is $275 including the shipping, at this site: link

 

[lorax]

Re: prop shopping

Thanks guys! This is why I love this forum.

 

[carljh]

Re: prop shopping

Mercury Laser II = Quicksilver Lightspeed

For the record my prop is a Quicksilver Laser II.