4-blade steering torque in the opposite direction of a 3-blade?

[Ron V]

Has anyone else experienced this? Both of my Trophy Plus props are inconsistent in the direction of the steering torque, and actually tend more to torque to the left, while my SRX props torque very consistently to the right. The Trophys take less effort to steer overall, but are unpredictable in their behavior when trimmed out. I do run the Trophy 1/4" higher than the SRX and that helps. But to really cure it, I'd have to go 1/4" - 1/2" higher and that starts to kill the bow lift and raise the RPM while dropping speed. The boat is my Rapid Craft Hurricane, which is a V-bottom with lifting strakes but no pad. It likes to run with the shaft about 3" below the bottom.

Overall I've just dealt with it for years when running the Trophy and used caution when driving through irregular surface conditions. But a couple weeks ago the boat got pretty out of shape and I was barely able to get it under control. I definitely made a couple of mistakes in a row so I'm not blaming the boat, but I know that if I had been running the SRX it would have just been another couple of small boat wakes. It just seems counter to the folklore about 4-blade props being easier to drive. If the steering torque is all to one side, then everything is predictable. Split it up and things get interesting in less than ideal conditions.

It's worth noting that I tried a Shooter on this rig once and did not have any indication of this problem.

Lower unit is a stock 4.75" fishing case. Skeg does not have a torque tab because even with the SRX it was never hard enough to drive to really need one, and with the Trophy pulling the opposite way half the time, it didn't seem to make sense to try to put one on.

[rgsauger]

What motor and what kind of speeds are you seeing? How much setback?

[OnPad]

Neither one of those props has a extreme amount of torque load......., compared to a large diameter 4 blade.

The height of engine has a lot to do with how much prop torque your going to have. Every boat is different, so I'm guessing, but if engine was raised, you would have less twist in boat but have more load on steering.

Your v hull boat with no pad is one of the hardest designs to get to run down the lake, without bouncing gunnels off the water.

Have you tried a tempest? At your engine height I had much better luck than a trophy.

[Ron V]

Neither one of those props has a extreme amount of torque load......., compared to a large diameter 4 blade.

The height of engine has a lot to do with how much prop torque your going to have. Every boat is different, so I'm guessing, but if engine was raised, you would have less twist in boat but have more load on steering.

Your v hull boat with no pad is one of the hardest designs to get to run down the lake, without bouncing gunnels off the water.

Have you tried a tempest? At your engine height I had much better luck than a trophy.

It's not the amount of the steering torque, it's that the Trophy is unpredictable on which way it is going to yank at a given moment. Other than that it's a great all-around prop. Raising the Trophy up another 1/4" actually reduces whatever steering torque it has, but slip goes up and speed drops. Raising the SRX increases steering torque with no benefit in speed or handling. No problem there; the SRX drives just fine anyway.

This boat is actually pretty stable as long as the torque is consistent so that I know how to respond. The inner strakes end a couple feet ahead of the transom, so it runs on the very rear of those. Can hang it out all day once you get the hang of it. Irregular water conditions are just much more challenging with the Trophy than with the SRX. I haven't tried a Tempest...that might be interesting. It runs great with the SRX...just not the best for getting on plane with passengers.

I've been driving this setup for 18 years, but have just always wondered if anyone else has had a 4 blade torque in a different direction than a 3 blade, all else being equal.

Running 6" setback, top speed 71-72 with the Trophy Plus and about 73 with the SRX.

[OnPad]

Nice boat! Not much of it in the water at speed!

I have a 26p trophy that I tried on a 20ft champion, and bullet. It slipped very bad at the depth your running. I could only get it to hook up somewhere around even with the pad (Bullet boat) never could get it to run on the champ. Which I run a 25p tempest (-3"). Was way better for that boat. The trophy is easy to drive, but slower compared to a larger 4 blade et, on my bullet anyhow. Different boats, so I don't know if any of this is relevant for you?

I still say motor height is huge factor in the amount prop torque effects boat. But, your right near the height of losing bow lift, and needing a nosecone. My lighter junk don't like to run right and fast till the prop shaft is above the bottom. At that point I had to pitch up, blade up, diameter up, and then you get a ton of side load on steering.

Probably easier for you to move some weight around your boat, or just use a different prop, vs. a refit, to change motor height. Try a tempest, I think you will like it.

Did I say? Nice boat!

[KIRCHNER]

Your not alone, my set-up pulls to theleft at 40, then goes thru a 0 range up to around 60, i can take my hands off wheel, wide open pulls hard to the right, two hands on for sure, with hyd.steer..

[OnPad]

Your not alone, my set-up pulls to theleft at 40, then goes thru a 0 range up to around 60, i can take my hands off wheel, wide open pulls hard to the right, two hands on for sure, with hyd.steer..

Two out of three of my boats have double rack cable, the one that runs -3 ain't bad. The one that runs +2 is a handful and a half!

[OnPad]

I'm off topic again, but here's a model boat with a similar design. It runs 45mph+/- on the ragged edge. If I run a bigger, or 3 blade prop on it, she's bouncing off the rub rails. If I wanted to go faster I would spin the motor alot more rpm, and run a smaller prop.


O.P.'s boat might be real finicky about props. Not like stern lift, blade diameter, or 4 blades. Think srx, drag, et, chopper, tempest?
You could also just need to move ballast in boat, according to whichever prop your running?

[Dave S]

Yaaaaaa......Had same...... going thru the trim range......Had wheel pulll difffereny........

[Ron V]

Yaaaaaa......Had same...... going thru the trim range......Had wheel pulll difffereny........

Had that too. But this seems to flip-flop even at a given setting.

[Dave S]

Nice Boat..... did some one say that...........I would try a small tab on the skeg......Is your steering Tight ? .....I only see one cable in the Pix.......