Another Prop Question

[directmule]

This is what I have, 2006 Yamaha F150 4 stroke Manual say’s 5000-6000rpm Full Throttle Operating Range (Maximum Output 150hp @ 5500rpm) I like the 5500 figure better than the 6 grand one, we’re talking a 4 stroke outboard here not an indy car.

When we first got the boat in 2008 it would hit 5100rpm but since then and adding two large #31 AGM batteries, trim tabs, huge wash down pump, s/s arch, radar, pot/anchor puller, anchor, chain & rope, guest charger, etc etc it will only hit 4600/4700rpm trimmed out.

I have a 14 x 19p Quicksilver #2016P19 3 blade aluminum prop, thinking of keeping this one for a spare and going to a 4 blade s/s (I like shiny things)

From what I understand, every 1” in pitch change is around 150 – 200rpm change roughly, going both ways, either up or down depending on which way you go, in my case it would be down. So if I can only hit 4700rpm and want to hit 5500rpm I would theoretically go to a 15” pitch but when you go to a 4 blade s/s you don’t need to go that much of a drop. Question is should I go with a 16” / 17”, still staying with the 14 or 14.25 dia. Not looking for top end speed, looking for good cruising/fuel economy speed.

Next question, boat now, as loaded, does 25mph at 3300/3400rpm and fuel meter say’s 5.8/6gph and if I keep track of mileage and fill it up, it’s pretty damn close to it’s figure. What is this different prop going to do to those figures?

Dennis

 

[TheBigGuy]

Hi Dennis.

Sorry to say it, but you are way over propped. You should be looking to turn at least 5700-5800 rpm. Four strokes are designed to perform their best when they can reach the top of their recommended RPM range. You are lugging your motor, and that is not good for engine longevity. You will need to drop to a 15 pitch prop to get even close to where your RPM's should be at. A prop that is 15 pitch with three blades should turn higher than a similarly designed prop of the same pitch with four blades. That means you probably won't realize as big a gain in RPM's by dropping to a 4 blade 15P vs a similar 15P 3 blade prop. Also, a stainless prop of the same pitch and design will usually turn lower RPM's than a similar prop in aluminum. The more variables you change the harder it is to predict how big the change in the RPM's will actually be. Go with the smaller diameter size blade as this will usually help produce higher RPM's, although a 1/4" change in diameter probably isn't big enough to make much of a difference.

You really can't predict what your actual RPM's will be until you test a new prop on the water. Try to buy the prop from a shop that will let you exchange if it isn't the correct pitch. Stick with the same brand and number of blades when testing out new props. Props vary widely in their design, and two props of the same pitch from different manufacturers may turn at very different RPM's. If you test out similar blades from the same manufacturer it will be much easier to guestimate what changing the pitch will do to your RPM's.

A four blade will probably give you better gas mileage at cruising speed. There's really no way of telling though until you test different props under similar conditions.

Do some research on the boating sites before you commit to buying. Try to find which props performed best on similar boats to yours with similar engines. That will help you decide on what may be the best prop to try out on your boat.

Check on the iboats site for researching prop questions: http://forums.iboats.com/forumdisplay.php?f=35

Best of luck to you finding the right prop.

 

[Clipper]

Ah, the age-old problem of finding the 'right' prop. We've all been there and it always seems to come down to the 'try a few and see which one works best for you' scenario. You can read everything available on prop selection and you still cannot be sure how any given prop will actually perform when connected to your rig.

Too bad some whizz kid could not come up with an application/database that you could plug all your variables into (motor size and type, boat size and type, weights on the water, usual conditions, rpm expected, any performance issues to be addressed and on and so on (I'm sure that we could think of a bunch more) which could then search the database of props that fit your engine and give you a recommendation (or at least a place to start from).

This would be a great tool and maybe save many fruitless hours searching the web and trying to guess if such and such a prop will actually work the way I want it to but I think it would still come back to the 'try it and see' method in the end.

 

[CIVANO]

http://v2.propellerwizard.com/index_iframe.php?accountID=5Ymov3969F4455xxl1J6e81c3969P413138vY

http://www.ptprop.com/index.php?option=com_artforms&formid=4&Itemid=60

 

[directmule]

Not too many 4 blade s/s props for the Yamaha F150 but did come up with a few.

Solas - Titan HR4 14.25 x 15p # 3553-145-15
Michigan Wheel – Apollo 14.625 x 16p # 993203yam
Turbo – 2+2 TH Series 14 x 16p (no number)
Stilleto – Bay Pro ll 14.25 x 16p # 805416-505
Stilleto – Bay Pro lll 14.25 x 15p # 807415-505
Stilleto – Bay Pro lll 14.25 x 17p # 807417-505

There are lots of other 4 blade props but their pitch is 18 and higher and since I need to go lower than 19 these are what I found, same thing with the 3 blade props.

Also a few 3 blade s/s.

Michigan Wheel – Apollo 14.375 x 15p # 993042yam
Michigan Wheel – Apollo 14.25 x 17p # 993043yam
Michigan Wheel – Ballistic 14.875 x 15p # 345931yam
Michigan Wheel – Ballistic 14.75 x 17p # 345932yam
Quicksilver – Silverado 14.5 x 15p # QS5050X
Quicksilver – Silverado 14.5 x 17p # QS5052X
Yamaha – Reliance 14.5 x 15p # 68F-45970-00-00
Yamaha – Reliance 14.25 x 17p # 68F-45972-00-00
Turbo – 2+2 TH Series 14.25 x 15 (no number)
Turbo – 2+2 TH Series 14.25 x 17p (no number)
Stilleto – Advantage ll 14.25 x 15p # 800315-505
Stilleto – Advantage ll 14.25 x 17p # 800317-505

I’m kinda leaning on the 14.25 x 15p or 16p but will have to go over to Precision Propeller in Surrey and have a talk to them otherwise I may just have to print this chart out, nail it on the living room wall and go to the far side and see where the dart lands.

Thanks to all who replied

Dennis

 

[wildwest]

Go with the Michigan wheel-Apollo 14.625-16 #993203yam,4 blade stainless.Any lower in pitch and you will be at too high an RPM and your gallons per hour will increase too much.Just remember...HIGH RPM -HIGH FUEL BURN. A 16 pitch will be the SWEET spot.You can get one online from the us for maybe $250 plus 45 shipping UPS.The prices up here are double that.....I had one shipped up for my 225 opti ..$ 270.plus shipping...nice prop[Apollo]..make sure you order the slide in hub kit if needed another 14 bucks..good luck

 

[TheBigGuy]

I think if you go with one of the Stiletto props you will be happy with them. Bay Pro II would be a good choice, but I think you'll need to step down to a 15 pitch. Bay Pro III is also a highly regarded prop, and may be the best choice as it is available in 15P.

I am currently running a SS 17P Stiletto Advantage 1 on my motor (Merc 115 hp 4 stroke) , it is a great prop. I also have a 17P Michigan Wheel Rapture SS, and a 15P Solas SS that both run very well on my on my boat. I wouldn't go for the Apollo prop, from what I've read you may be disappointed. The Turbo 2+2 has a great reputation. The Solas HR Titans also have a good reputation, and they are a good value compared to the cost of other props.

Stainless props have far more aggressive cupping than aluminum props. You might think going down to a 15P is too low. However with the extra cupping on stainless props they may turn lower RPM's than you would expect for the pitch. Turbo props are well known for having a higher effective pitch than what they are rated at.

Hope some of that helps in making your choice.