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Need a new prop for my 112 Johnson SPL

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  • Need a new prop for my 112 Johnson SPL

    I have a 16ft Aluminum Sylvan Sport Select. The weight of the hull is around 840lbs

    (http://boatspecs.iboats.com/Sylvan_M...95/bp/66b91289)


    Mainly I use this boat for towing kids tubing, towing one, sometimes two props with two kids who are about 100lbs. Inside the boat are my wife and I and gear. The hull has a 750 lbs max rating for gear and people and I'm usually right there if not over.

    Originally it came with a 3 blade 15 pitch aluminum prop; but that cavitated like crazy in turns, so about 24 years ago I got a four bladed comp prop (I had no money) with a 17 pitch. It's worked great for me so far, though I can overspeed the engine a bit (I can top out around 5700 rpm if I let it at WOT, and it will get me maybe 37mph with everyone and a full tank of gas, but that is nearly fully trimmed down because the boat loves to porpoise).

    So, last year, I dinged the comp prop, and I need something new. What are my options? I've been online and I was hoping for 'Here is your boat engine, here are the 5 available props, with reviews' almost like buying a tire, but it seems like there is nothing like that. Just lots of choices and little idea of how it will perform.

    So my questions are:

    * Is there a performance difference of composite vs aluminum vs stainless steel? If so is it significant?

    * If so, how does that affect pitch and blade selection? I went to four blade due to cavitation on my aluminum in turns. But would a Stainless eliminate that?

    * Is there a place to go for reviews? I'd be awfully upset to get a 3 bladed stainless prop and have it not perform, or have it cavitate, given the price on these things.

    * are there good/bad makes and models of props?

    * Should I get a cupped prop?

    * are there good/bad retailers?

    * are there gotchas (I.E. if I have a prop strike with a stainless do I need a new lower unit because the stainless prop won't bend or break?)

    In my platonic ideal of prop shopping, I'd go to a store where a guy could look at the boat and my use and give me four to try for a day; and at the end I'd buy one. But that doesn't seem realistic.
    Last edited by Jimwhall; July 9th, 2019, 09:19 AM.

  • #2
    Originally posted by Jimwhall View Post
    I have a 16ft Aluminum Sylvan Sport Select. The weight of the hull is around 840lbs


    Mainly I use this boat for towing kids tubing, towing one, sometimes two props with two kids who are about 100lbs. Inside the boat are my wife and I and gear. The hull has a 750 lbs max rating for gear and people and I'm usually right there if not over.

    Originally it came with a 3 blade 15 pitch aluminum prop
    So my questions are:

    * Is there a performance difference of composite vs aluminum vs stainless steel? If so is it significant?

    * If so, how does that affect pitch and blade selection? I went to four blade due to cavitation on my aluminum in turns. But would a Stainless eliminate that?

    * Is there a place to go for reviews? I'd be awfully upset to get a 3 bladed stainless prop and have it not perform, or have it cavitate, given the price on these things.

    * are there good/bad makes and models of props?

    * Should I get a cupped prop?

    * are there good/bad retailers?

    * are there gotchas (I.E. if I have a prop strike with a stainless do I need a new lower unit because the stainless prop won't bend or break?)

    .

    Your engine has a WOT rpm range of 4500 - 5500.

    I feel a 15 is not enough pitch for you app, provided your engine is up to snuff. A 3 blade 17 will usually put you in the upper half of that range, and at about 40 - 42 mph. I can't see it turning 5700 and only getting 37mph, unless it has a very poor grip on the water and you are experiencing high slippage.

    Your ???s

    1) Different Materials have different properties in regards to Strength, Weight, and Flexibility. Plastics tend to be light, and very accommodating regarding being the Sacrificial Limb. but the blades will flex under load and usually are thicker which reduces Efficiency. SS is at the other end, tough, durable, and strong, it permits thinner blades and more aggressive blade design and shape. which can offer designs capable of higher performance, or greater durability. However its great Strength can also be a Liability in locations where there is a chance of a Hard Strike(ROCKS), Internal Damage to the drive train has been known to occur(broken/chipped gears, bent propshafts, twisted propshafts/driveshafts. AL is a good Compromise, Strong, Inexpensive, Repairable. Being a weaker metal, its thicker blades will not be quite as efficient as SS, but it too will less likely to transfer the shock of an impact through to the drive train.

    Don't get caught up in the hype regarding 'AL props flex too much'. That was a great line by Marketing and has sold a lot of SS props. The flex on an AL prop, might be 1/50" on a 20" pitch. Grab a blade with a pair of Channel Locks and try flex it...

    2) Number blades has very little to do with its ability to resist Ventilation. Props with cupping and greater Rake are more resistant to Ventilation because design, SS being stronger allows for thinner blades which are more likely to retain a grip on the water.

    3) Reviews are available here and other websites. But they need to be take with a grain of Salt. What works for on boat/motor/usage, may not be the best choice for another. Sometimes a person gets lucky and finds a good choice quickly, other times, many props are tried trying to find the best over all prop. SS props can get expensive, I have 3, they are currently selling for on average $900(CAN) each.

    4) There are Excellent and less than Excellent Props for sale. There are Motor Manufacturer Brands(Mercury has been making some of the Best props for over 60 yrs). For the past 15 years, their props can be used on just about anything made the past 50 yrs, some exception though. OMC/BRP also make some excellent props.
    There are 3 party brands, of which some are good, others... Some are a Price Point prop, but I feel you get what you pay for...

    5) most props, since the late 70s are cupped.

    6) this was spoke of in #1

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    • #3
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      I did a turning point 3 blade, 14 diameter x 13 pitch on my Wellcraft 190 ccf. 1995 Evinrude 112, boat, fuel and people probably give it a total weight of 2700 pounds or so. It planes pretty fast and the engine likes to ride at 5000 rpm with the boat going 24 mph, with the 13 pitch prop. I do have to watch out for exceeding 5500 with the 13 pitch prop. Granted I have a heavy boat, so I prefer power and faster planing than top end... With a 13.75 by 17 pitch (that was originally on it) I could get 31 mph, but it took forever to plane and the engine would not turn more than 4300 rpm's. Top speed with the 13 pitch is 26 mph... This set up is what worked for me. Between the prop and the adapter it was 130 bucks buying it on line. Hope this helps.

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