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I remember reading on the net more than once that a 4 blade prop improves performance on a tunnel hull boat. My new tunnel has a 3 blade prop.

Anybody know the difference and why 4 is better?

Going to git a camera tomorrow and post pictures of the bhote.

In general a four blade prop improves hole shot and lift. So with a tunnell hull it will lift the boat up higher improve draft. The sacrifice, there is always a scarifice, is that you will loose top end speed.

4 blade vs 3 blade

I don't think you would lose top end speed...4 blade will give higher engine height, less slippage.

copy from evinrude-parts.com website, The Outboard Wizard article:
3 Blade vs. 4 Blade

Performance boats: 3 blade fastest but in some cases the 4 blade will deliver more blow lift to achieve faster speed.

Advantages of a 4 Blade:
A 4 blade can be trimmed high to achieve higher transom height, which will achieve higher speeds.
A 4 blade propeller has less slippage. Due to better hole, a 4 blade will stay on plane at lower RPM, and will improve gas mileage.

Read Entire Article...
http://www.evinrude-parts.com/Outboard_ ... mance.html

Just my two cents, and based on the only boat I've ever had with a Jack plate and 4 blade prop.............I dont think I would get the full advantage of the JP w/out the 4 blade. My boats not a tunnel but I would think that the name of the game is to use as much of the water funneled thru the tunnel as possible. Add to that that the engine is jacked up 3,4,5 inches and set back 4inches, you'll need as much prop in the water as you can get. Here is a video of a non tunnel running a JP and a 4x prop. Only about half of the prop is in the water, don't think a 3x would hold its bite.
prop video fast forward to about 3:00min to get beyond the sales pitch.

Three advantages to 4 blade with tunnel hull:
1. quicker hole slot
2. more control in turns
3. keeping boat on plane at much lower speeds

Disadvantage:
1. less top end

Draw:
1. I seem to hit rocks and bars with each about the same

My 90 Yam with 3 blade turns 5500 top end....5100 with
four blade. Once up I can keep boat at plane about 12-13 mph
with four blade and hardly less than 16-18 with the tri blade.

Hope this helps!

I have the same motor (Yammie 90 2S) and I am thinking seroiusly about the 4blade. I have read it also helps reduce cavitation which seems to be an issue with my rig. I just have to eat up the current prop before I can spend $400 on a new one though. Don't have that kind of money laying around to throw at something that isn't broken.

Note - Going from three to four blade props you need to drop down in pitch 1-2" or you will not be turning the correct amount of RPMs, if you were turning them right to start with

All points are correct to a degree, a boat is like a woman, each one is temperamental in it's own unique way

A four blade has less slippage because is has more surface area, more "meat in the water", it can be trimmed higher for the same reasons.

A four blade provides lift in two different ways, it provides bow lift and stern lift...some props provide more or less of the other.

Losing top end is not necessarily true, my boat being an example with a three blade prop, by myself, running with the wind, hat backwards and laying in the floor , I could hit 40 mph. With a tournament load and another lard arse (BD) I can only hit say 36 mph. I added a four blade prop, I dropped down two in pitch with a tournament load or by myself I can hit 36. I am less than 40, but I maintained my speed with a load and improved my hole shot, torque and running at higher motor heights.

well i will run the 3 blade that's on there at first and see if i think i need better performance

Saw where Scandy White makes a custom 4 blade prop that works with their style tunnel. All the boats come with them. My boat had one but the previous owner changed motors and now it has the stock 3 blade on it.

Gonna save some change and get the 4 blade for spring.

Ran the boat for the first time yesterday, and we had some old gas problems. Didn't drain out the old gas.....finally got that out and it ran better.
Still gonna run some seafoam in it today, it still run a little ruff.
Love the way this boat handles!

Ok...went to the Flint in Bainbridge today. I am liking this boat more and more! Ran it 23 miles up and back.

I am definitely going to get a 4 blade prop for this boat. Running the 4 stroke shows me I need a much better hole shot!

I have always had 2 strokes. There is a difference. I got great gas mileage...about 6 -7 miles to the gall.

With the 3 blade I was running about 28-30mph. My buddy had the GPS in his boat and he was at 25...and I left him in about 2 bends of the river.

Until I figured out the trim, I was riding a porpoise!!
Still had a little of it at the best trim setting. Hoping the 4 blade will cure that. Also a lot of weight in the rear with me only in the boat. Me, gas tank, 4 stroke 40 hp.

The sponsoons are a must on this rig.

Got ta git it right!

I know it's more money but a set of lenco tabs would would solve the bronco ride on that machine. Since you don't want to fish with 100lbs concrete block in the front of the boat, just a little bit of tab gets you the same effect. In the process it also raises the stern ( shallower running and hole shot) just my .02.

I thought about the tabs yesterday. I think I'll wait and see how the 4 blade prop affects the bronco Billy machine. I'm going to call Scandy today and see what they have to say.

The 4-blade will give alot more lift and should help the porpoising....You will luv the 4B

Rats!....4 blade prop..$400 (?)....saltwater trolling motor..$500

Just spent $450 on repairs.....and he still has it today cause it wouldn't stay cranked on idle.

$150 on a skeg guard from Wavel....

About $1800 retail barter on the boat....

Man...maybe I should find another (cheaper) addiction?

Previous owner said today that on the original motor he had a stingray on the motor and it helped the hole shot a lot.
Said when he got this new motor he didn't use it enough to fine tune all that. Now it's my project..

Bring Out Another Thousand