VViCKiD Posted February 18, 2014 Share Posted February 18, 2014 Hi guys, After reading a few posts, I was thinking I should upgrade my rig and try get a SS propeller. I have a haines hunter 530 with a 2002 yamaha v4 2 stroke outboard. Just wondering, does anyone knowwhich propeller would be best suited for this ? Also, how would you go about deciding on the pitch etc ? Link to comment Share on other sites More sharing options...
a boat Posted February 18, 2014 Share Posted February 18, 2014 Hi, any outboard, any technology have an ideal WOT RPM they want to reach for the best performance. A V4 like yours wants to see about 5500RPM at WOT and what determines that is the pitch of the prop. You will need to find out what pitch you have now and what your WOT RPM and then you can determine what a SST prop will do. All else being equal a SST is easer to turn than an alloy prop so if you have say a 17 inch at the moment (which I am guessing you will) and she turns good RPM then a 19 inch SST might suit. Best to go for a WOT run with your normal load and see what RPM you are doing and we can go from there. Proping is a black art though and only way to know for certain what any prop will do on any boat is to try it, but there are rules of thumb and experience is very important. Cheers, Huey. Link to comment Share on other sites More sharing options...
VViCKiD Posted February 19, 2014 Author Share Posted February 19, 2014 Thanks Huey. Please excuse my lack of prop knowledge, but how would I go for a "WOT" run ? Link to comment Share on other sites More sharing options...
a boat Posted February 19, 2014 Share Posted February 19, 2014 Hi, WOT mean Wide Open Throttle, so put her in the water with normal load and push the control lever as far forward as she goes and watch the RPM on the Tacho-around 5500 will man the current pitched prop is the right pitch. Cheers, Huey. Link to comment Share on other sites More sharing options...
VViCKiD Posted February 19, 2014 Author Share Posted February 19, 2014 Thanks Huey. Will give it a run ! Cheers Link to comment Share on other sites More sharing options...
dogbox Posted February 21, 2014 Share Posted February 21, 2014 Hi mate Props can make a big difference to your boats performance according to how you use your boat, I give this an example, My first boat 4.5 sundance with a 40hp I had three props that I played with on this boat, . 10.5 inch prop for towing the kids on the ski's etc high fuel consumption good power, . 11.6 inch prop standard for the engine . 13 inch prop gave me really great fuel economy when I was out fishing doing the KM My mate Glen has a Vindicator 200HP he changed from a 3 to 4 blade SS prop and cut his fuel consumption in haft So I guess you need to think about how you use your boat With my 115 Yamaha I thinking to change to a 4 blade SS with the same pitch, because I troll and punch through the wave about 25-2800 rpm and I think I can improve the boats performance and save some fuel, Keep in mind that there are a number of other factors in play like engine and boat type, and even how your leg death is positioned on the back of your boat Dogbox Link to comment Share on other sites More sharing options...
VViCKiD Posted February 21, 2014 Author Share Posted February 21, 2014 How fuel consumption by half! Yeh my primary objective is fuel efficiency So perhaps 4 blades is best. Please keep me posted on how u go with the 4 blade Link to comment Share on other sites More sharing options...
tasksta Posted February 21, 2014 Share Posted February 21, 2014 My boat has always been a guzzler for its size and weight. Jonno 70 has 14 x 17 prop, after lots of reading it should really have a 13 x 17 or 13 x 19 in ss. Will one inch diameter really affect fuel consumption that much? Sorry to hijack OP Link to comment Share on other sites More sharing options...
a boat Posted February 21, 2014 Share Posted February 21, 2014 Hi, no matter what brand or technology an outboard is making sure the engine gets it correct RPM at WOT is very important for fuel economy, performance and engine life. Nothing worse than lugging an outboard (it will be like going up a never ending hill in your car in top gear-they will not like that). The 70HP Johno is a built proof engine and was made for over 30 odd years and with the correct set-up they are as good as any carby engine on fuel burn. The diameter is irrelevant to a degree and pitch is what determing RPM and not many 70HP's could turn a 19 inch prop and still be in the ideal RPM. Best to see around 5600RPM with your Johnson. Cheers, Huey. Link to comment Share on other sites More sharing options...
tasksta Posted February 21, 2014 Share Posted February 21, 2014 Ok thanks mate, its at 5500 WOT so something must be right. Is it normal for the prop to be within 1/8 inch from the top plate? Cant even get a finger in there. As for the Jonno yes it has not missed a beat since you did the pump diaphragm. Link to comment Share on other sites More sharing options...
a boat Posted February 22, 2014 Share Posted February 22, 2014 Hi, yes some high rake props have very tight tolerances to the AV plate. Good RPM and good to hear. Save your pennies and if you swap out to a SST prop there can be benefits, but in all honestly with a properly propped engine like yours I highly doubt you will see your fuel bill halved. Cheers, Huey. Link to comment Share on other sites More sharing options...
BWV Posted February 22, 2014 Share Posted February 22, 2014 Guys, When I have been playing with props and engine height I have always aimed for 200rpm lower than the recommended maximum rpm of my outboards at an average/normal load in the vessel. With this set up, when I was loaded for bear my rpms would drop a little bit but they stayed in the recommend range and when I was light the rpms wouldn't exceed the maximum rpm set out by the manufactures as the rpm's increased as the vessel was lighter and faster. As for 3 vs 4 blades, in general a 3 blade prop is more efficient than a 4 blade. In a perfect world a 1 blade prop would be the best for effiency, but I leave that to someone else to make work. If you want better maneuverability and slow planning speed a 4 will work best. The 4 will also give you more stern lift. For the faster cruise and top end a 3 is the way to go. 3 usually give better bow lift. Engine height is also very critical when selecting/ changing props, make sure your AV plate is visible and just clear of the running surface of the water when on the plane at your cruising speed and trimmed correctly otherwise you'll be wasting your time and money on new props. Link to comment Share on other sites More sharing options...
VViCKiD Posted February 22, 2014 Author Share Posted February 22, 2014 Thx for the response guys. I tested my boat out today. It hit 30 knots at 6700 rpm. My goal is efficiency. So does this indicate I should have a look at a different prop ? Link to comment Share on other sites More sharing options...
BWV Posted February 22, 2014 Share Posted February 22, 2014 (edited) What's your prop pitch? 6700 rpm seems far to high and 30 knots is far to slow, was that off a GPS? I suspect you should be seeing around high 30's low 40's knots with your boat. I think 5500rpm would be maximum and I'd be aiming for 5300rpm. What hp you have 115/130? Do you know your gear box ratio? Assume it's 2.0-1 and I'll use 17 and 19" props. These calculations are using the number provided in this thread by yourself and Huey but I have a feeling your rpm or the speed is incorrect. With the 17 you have 36% prop slip, and I'd say your losing up to 30% performance/efficiency with that set up. If you have a 19 you have 43% prop slip and are losing up to 35% performance/efficiency. With a 19" prop, 2.0-1 gearbox ratio, the outboard getting 5300rpm, boat speed 39 knots you should see 6% prop slip. I'd say your boat would be around 37 knots with these figures at 10% slip which is a pretty good result. For your info we have 6% prop slip on my brothers boat after we mucked around with it and that's about as best you'll get while keeping you within the recommend rpm range in most conditions. If you can double check all your figures I'll get you a correct answer and some ideas on what to do. Can you get a photo of your AV plate when on the plane at say 4000-5000rpm and trimmed correctly. One other thing SS props are more efficient than alloy ones. Edited February 22, 2014 by Whaler 255 Link to comment Share on other sites More sharing options...
tasksta Posted February 22, 2014 Share Posted February 22, 2014 Sounds like you need more pitch to reduce WOT. Link to comment Share on other sites More sharing options...
VViCKiD Posted February 22, 2014 Author Share Posted February 22, 2014 My prop pitch is 17". To be precise, it says 13 3/4 X 17 on the propeller. Gear ratio is 2.0:1. The rpms were taken from a telflex taco that I have installed on the boat. And the speed was taken from a lowrance HDS 7 fish finder combo (Speed On Ground) measurement. The boat was tested with 3 guys on board. What's an RV plate ? Is that the anti-cavitation plate ? Thanks in advance ! Link to comment Share on other sites More sharing options...
VViCKiD Posted February 22, 2014 Author Share Posted February 22, 2014 Oh and I forgot to mention, the full throttle operating range is 4500-5500 rpm. If my taco reading is incorrect, how would I verify this ? Link to comment Share on other sites More sharing options...
VViCKiD Posted February 23, 2014 Author Share Posted February 23, 2014 I also just tested the idle rpm's by flushing the motor. The outboard idles around 1000 which is a tad high (manual says 700-800) should b ideal. Should I be concerned by this? The fact that it idles at say close to spec and comes up with a reasonable figure for the rpm's, suggests to me that the rpm's displayed when I do a WOT test is roughly correct. Link to comment Share on other sites More sharing options...
BWV Posted February 23, 2014 Share Posted February 23, 2014 (edited) If your outboard is spinning to 6700rpm With a 17 I suspect your gauge is reading incorrect. Huey May be able to confirm or deny???? With a 17 you should be seeing numbers pretty similar to this: 5300rpm 34 knots 9% prop slip With a stainless steal prop I'd probably try a 19 if you can you hands on one all you should get numbers close to this: 5300rpm 38 knots 8% prop slip As mention earlier at medium loads you should aim for slightly lower rpm's if possible so you don't exceed the maximum rpm when your light. Edited February 23, 2014 by Whaler 255 Link to comment Share on other sites More sharing options...
BWV Posted February 23, 2014 Share Posted February 23, 2014 Or your taco could be 20% out???? Link to comment Share on other sites More sharing options...
VViCKiD Posted February 23, 2014 Author Share Posted February 23, 2014 Thanks for the reply whaler. but im Not sure what you mean by "garage". R u suggesting the rpm's I'm seeing is incorrect? Cheers Link to comment Share on other sites More sharing options...
BWV Posted February 23, 2014 Share Posted February 23, 2014 (edited) Thanks for the reply whaler. but im Not sure what you mean by "garage". R u suggesting the rpm's I'm seeing is incorrect? Cheers Changed, gauge, bloody auto correct.Yes I suspect so. Edited February 23, 2014 by Whaler 255 Link to comment Share on other sites More sharing options...
VViCKiD Posted February 23, 2014 Author Share Posted February 23, 2014 oh right.. thanks whaler. do you think it's the "brand of gauge" or a faulty one ? Link to comment Share on other sites More sharing options...
VViCKiD Posted February 23, 2014 Author Share Posted February 23, 2014 I just re-calibrated the gauge. will test again when I get the chance. Thanks for the pointers guys. Will keep u posted Link to comment Share on other sites More sharing options...
VViCKiD Posted March 10, 2014 Author Share Posted March 10, 2014 So just an update to this, it turns out my tacho was calibrated incorrectly. Was out by 20% (I checked with a hand held digital tacho). Tested the boat out on the weekend with usual load. Hit 5200 rpms at WOT and top speed of 34 knots Thanks all for the help ! Link to comment Share on other sites More sharing options...
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