4 blade prop for 140

[winston]

I am cosidering changing my 19" 3 blade prop for a stainless 4 blade prop. The reason that I would consider this is that I believe that a four blade prop would provide better holeshot and better stern lift. If I did change, what pitch would I need? The motor is a 2010 Suzuki 140 fourstroke and does reach 6000 rpm at WOT. The boat is a Stessl 5.6 m half cabin. Cheers Winston.

[Blackened]

G'day

General rule of thumb, drop an inch in pitch for the extra blade.... first things first, how's your engine height?

Dave

[winston]

Blackened, engine height is fine, could go up 1 hole at the most. I checked with a dealer at the 20h service and he agreed height is ok. Cheers Winston.

[Chimo]

But where is the cav plate sitting when your planning?

C
C

[trueblue]

1" of pitch for an extra blade, and another extra 1" of pitch if cupped heavilly

[grammel]

I changed the prop on my 135 merc two stroke to a 4 blade stainless,also to get more stern lift etc.The best way i found was to reserch on the net and then go to my merc dealer with some ideas and make up my mind listening to thier advice.Worked for me i, bought a mercury 4 blade stainless and achieved the desired result.

[tropicrows]

I have a 2005 140 suzie, just be sure you can exchange it if does not live up to your expectations. I went through the same excerise and ended up with another 3 blade prop. The 4 blade gave me great hole shot and stern lift but fuel usage was up also. There are many threads on here on props, including my own with test results

[Salad Fingers]

I would have thought the 140zuke would give you more than enough hole shot on a 5.6m alloy already?! :)

what sort of speeds are you getting at WOT? i'm wanting to whack a 140zuke on the ass of my rig.

[winston]

Salad Fingers, 33 knots at WOT, this agrees with a test that trailerboat magazine did on the same combo. Cheers Winston.

[stue2]

But where is the cav plate sitting when your planning?

C
C

Think you will need to check engine height on the water not on the trailer.

Stu

[robothefisho]

I'd be thinking sort engine height first, because top speed seems pretty low considering the boat and engine combo. From memory it's a 5.6 m stessl? Pretty light weight and reasonably flat bottomed. Really think you should be getting 36 knots minimum. But certainly a 4 blade prop will improve holeshot and would probably benefit that hull immensly.

[winston]

ROBOTHEFISHO, yes, I thought about 36 knots. The hull mass is approximately 650 kg, it's 4mm bottom and three mm sides in 5083 plate aluminium. The bow is quite sharp with a very moderate V at the stern. The hull likes the motor to be trimmed in especially in rougher water which is why I thought more stern lift would be benificial. The ride is very good but the holeshot and top end are a little disappointing. Cheers Winston.

[bigjimg]

Winston my Signature gets 33knt at 5200 rpm,my hull is much heavier than yours.I think you should lift your motor that extra hole and just see what you get.You can always drop it back down if it doesn't work out.I am about to lift my motor one hole as my rpm dropped when i fitted my foil,will also check out a 4 blader once i have done that.Jim

[Salad Fingers]

yes seems a little slow at WOT, my 5.4m alloy with a 90 does 35knots WOT.
My motor can still probably come up one hole aswell.

[bigjimg]

I changed the prop on my 135 merc two stroke to a 4 blade stainless,also to get more stern lift etc.The best way i found was to reserch on the net and then go to my merc dealer with some ideas and make up my mind listening to thier advice.Worked for me i, bought a mercury 4 blade stainless and achieved the desired result.Gidday Grammel,what was your outcome?

[doublexl]

i would lift motor up a hole also.i've got a 140 zuke on a 6metre cruise craft [heavy] and i'm geting 34knots..

[doublexl]

also winston is your 19 a stainless prop? because there is a massive change by upgrading alloy to stainless.

[winston]

Prop is 19" alloy. I am now sure that I will lift the motor 1 hole higher. Thanks Guys, Winston.

[grammel]

Hi bigjimg. The outcome was that i did get stern lift and the boat rode better offshore and i didnt need to adjust the throttle as much in rough water,as the boat would hold a constant speed much better, also wot is now 5600 revs whereas before with the 3 blade it would rev out to 6000.As for top speed may have lost a little,whith the old 3 blade 40 mph(gps is in mph) was easy, now i need to have everything just right to achieve this, meaning trim wind and tide. The boat jumps on the plane much better and gives great confidence at bar crossings.As for fuel consumtion, not sure havnt done any comparisons.Last of all the prop looks great .After the prop i added trim tabs and this made the boat as good as it could be.

[trueblue]

if you take your new 4 blade prop and get it re-pitched back a touch you will get your 6000 back... and make better even better again

[stue2]

Prop is 19" alloy. I am now sure that I will lift the motor 1 hole higher. Thanks Guys, Winston.

If it cavitates don't panic it's probably close to where it should be. The new stainless prop you put on will fix that.

BTW the cav plate should be on the water not in it.

cheers