3 Blade vs 4 Blade props
Printed From: The Fishing Website
Category: General Forums
Forum Name: The Boat Shed
Forum Description: Discuss all things boating.
URL: https://www.fishing.net.nz/forum/forum_posts.asp?TID=91333
Printed Date: 29 Jun 2026 at 2:14am
Topic: 3 Blade vs 4 Blade props
Posted By: Joker
Subject: 3 Blade vs 4 Blade props
Date Posted: 30 May 2013 at 11:49am
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Has anyone had any experience in running a 4 blade prop after a 3 blade? From what I have read there can be the following effects. Better acceleration Better low plane & cruise economy (this is of interest) Slightly lower top speed Need to go down 1" of pitch Is this true
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Replies:
Posted By: Kings Marine
Date Posted: 30 May 2013 at 12:56pm
First I will say that props are a black art and there dont seem to be many hard and fast rules but for your questions........ Better acceleration - Generally yes a better initial acceleration from a dead stop Better low plane & cruise economy (this is of interest) - from my experience, no Slightly lower top speed - in theory yes lower top end speed, but this is not always the case as I have had several boats that have a higher top end speed with a 4 blade than a 3 blade, if you do as per your next question then yes you will have lower speed as you have gone down in pitch assuming that the engine hasnt gone up in revs to counteract the pitch change. Need to go down 1" of pitch - no, although depending on who manufactures the prop it will be in either "even" pitch numbers or "odd" numbers so this may be different from the brand of prop already fitted to engine, regardless the engine must be propped to be in the manufactures rev range for the engine. ------------- The Mighty Waikato http://www.facebook.com/pages/Kings-Marine/100476476662857?%3Fref=ts |
Joker wrote:Posted By: Moki Marko
Date Posted: 30 May 2013 at 1:55pm
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I think you are right in theory Joker - but KM is right in practice. I certainly wouldnt go ditching my 3 blade prop if it was doing the job. |
Posted By: flyfisher
Date Posted: 30 May 2013 at 2:33pm
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Have tried a few 4 blade props in the Propulse range on under 50hp motors, understand they flex more due to the composite blades and they sucked top end speed off a lot compared to a 3 blade. It's a real science props, interesting some 4 blades are giving more top end, never knew that, but did hear a really good 4 blade in SS can achieve great things. From what I understand you'll get more bite 'out of the hole' with a 4 blade? ------------- https://www.youtube.com/user/troutboynz |
Posted By: Bounty Hunter
Date Posted: 30 May 2013 at 4:45pm
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4 blade props can theoretically be made with thinner blades because each only has to take a quarter of the load and not a third. if you can find a real high quality wheel with thinner blades, youll likely get the same top speed, as well as more grip and stern-lift. ------------- No disintegrations! |
Posted By: Murph
Date Posted: 30 May 2013 at 9:19pm
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I tried a four blade prop once and loved it, until I put it in reverse. It basically had no reverse thrust, it would just fizz up the water and not really give you anything in terms of bite. ------------- http://www.facebook.com/GForceLures http://www.gforcelures.co.nz/ [email protected] 0211640204 |
Posted By: Unclejake
Date Posted: 30 May 2013 at 9:44pm
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We use a SS four blade and an alloy 3 blade on a Yamaha F60 (they are different pitches. 12 and 13 respectively so speed and acceleration results are not relevant). The four blade allows the motor to be trimmed up noticeably further before it "grabs air". The four blade is also much less grippy in reverse (as Murph has just reminded me). Ours isn't a thin section though. It's quite a chunky and VERY heavy American brand (I forget which brand but it's something to do with Mercury). For us it has been great due to the extended range of trim
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Posted By: Kandrew
Date Posted: 30 May 2013 at 9:46pm
| Run a 4 blade on 6mtr tinny with 115 opti, pros are much better out of the hole, great trim control sits much flatter on the water in the corners and still has good top end 40 mph. Cons, average handling at low speeds and poor thrust in reverse but wouldn't go back to a 3 blade. |
Posted By: CoastalStan
Date Posted: 30 May 2013 at 9:53pm
| I changed to a Mercury Fury 4 blade on my 90 merc. Very grippy without any bowlift and no drop in top end speed. I only changed because it gave my boat the perfect WOT revs and an excellent cruise rev level. A 3 blade at the same pitch would have been similar but due to the huge pitch (23) i was worried about slippage off the mark, especially when crosing the bar. My reverse is exactly the same as the old 3 blade. Dont worry about blade numbers as much as the pitch. |
Posted By: Joker
Date Posted: 31 May 2013 at 12:04pm
| I have heard that the 4 blade provides stern lift keeping the bows down particularly at low plane speeds and stopping it bogging down when swells pass. |
Posted By: Ohsoslow
Date Posted: 31 May 2013 at 4:21pm
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I changed from a 3 blade to 4.. and love everything about it. BUT, the 3 blade I had on before, was apparently pretty average for my boat (Laser II). I have lost maybe a knot or two of top end, but have gained everywhere else, better accel, better economy etc. The guy I spoke to about it all, reckoned that he wouldn't recommend a 4 blade on a small-medium engine as they generally don't have enough torque to make the most of it. And he said the main benefit for me would be midrange cruising.. which is where I've noticed the most difference, For the same speed, I'm using 5litres less fuel, and I can cruise from 26-38knots, with the same mpg. However I have also been able to lift the motor up a bolt hole, due to running the 4 blade prop, which might be affecting the fuel use and performance etc. Also, I did drop an inch of pitch going from 3 to 4 blade.. and probably could of dropped another inch.
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Posted By: Spectrum
Date Posted: 02 Jun 2013 at 6:01pm
| I put a 4 blade on my old rig got an extra 7 kph right through the rev range but that was from replacing the beat up 3 blade factory prop |