So much prop wash I can’t steer the boat

Don S/V ILLusion · Jul 18, 2018

You have either a rudder problem or a prop problem or both. Or a really dirty bottom. Hope a C30 owner can advise on the most likely one. I would assume your boat can make 6 knots so it's likely the latter.

smokey73 · Jul 18, 2018

This is most certainly not a Catalina 30 design problem and I'm trusting some Catalina 30 owners will chime in to help you with your problem soon. Just think, if every Catalina 30 had the symptoms you describe they would all be in a scrap heap somewhere and most likely a class action lawsuit already take because there would be so many collisions somebody would surely sue. Also, any surveyor who did a sea trial would not let that go un-noted. Just saying. Did you have a survey with a sea trial before you purchased the boat?

It should be fixable but unless its just a dirty bottom (not likely though with the turning to port so dramatic) it will probably require a haul out to investigate and fix.

NoAgenda · Jul 18, 2018

I have a 1992 with a wing keel. There is some prop wash on the rudder that causes it to pull a bit. I can let go of the wheel but the boat will start to turn after a few seconds. I have a 3 blade Gori folder (15"x9") at 3000 rpm run at about 6.5 kts but our boat is full of cruising stuff. I don't normally motor at that rpm its to noisy, normally around 2500 rpm. which gets me around 6 kts.

Benny17441 · Jul 18, 2018

Concur with Don. Check the rudder first, does the problem persists even when the boat is strictly under sail? If yes it is the rudder , but if not look at the prop which could be fouled by growth or damaged.

jssailem · Jul 18, 2018

Matt. It is not an inherent boat issue. The Catalina 30 Boat design is excellent. But all boats even good ones can be compromised and exhibit bad behavior. Often the result of previous owner modifications or mishaps.
Welcome to the Forum. You are among a great group of sailors.
You state that the experience was when motoring. What is it like when sailing?
If sailing is ok, then we must look at the motoring elements. If you experience the same events when sailing then we must look at the boats hull elements.
Based on your question you have identified "Prop Wash" and "Motoring" as the culprit.
Prop walk (that turning feeling) is the result of a prop blade trying to push the water when driven be the motor. Different props create different prop walk. Sailing Mag produced a nice explanation (https://www.sailmagazine.com/cruising/walking-the-prop)
On your boat you can change the amount of prop walk by changing the propeller.
Which of the two props here give the greater prop walk?

You are correct. The one with the big ears.
What type of prop do you have? It may be a clue into solving your problem.

jviss · Jul 18, 2018

Interesting, John. I thought, though it wasn't prop walk, but asymmetrical prop wash. Maybe the prop is too close to the rudder?

Mweimer · Jul 18, 2018

All good points. The more I think about my own symptoms, I suspect I have a bad or incorrect prop on the boat. A clean, fresh bottom and running gear made no difference. It does not happen under sail, and I am over revving and under speed. Since each degree of pitch equals about 200 RPM, and I'm running at 3000, I would guess I need a prop with 2 degrees more pitch then I have. It could very well be I am throwing a ton of water at the rudder with no thrust. I could see how that could cause some interesting things to happen down there.
So, if anyone knows what size Fixed props they have on the 25 universal that works great please share, a prop change will be my next step.
No Agenda, I see you have a 15"x9 Gori. First, I'm jealous, that things probably worth half the value of the boat! second, I wonder if the proper fixed size translates to the same size in a folding prop, I would love to not drag a 3 blade fixed prop all the time.
Thanks!

jssailem · Jul 18, 2018

jviss said:
it wasn't prop walk, but asymmetrical prop wash.

Identified in engineering terms I agree.

jssailem said:
Prop walk (that turning feeling)

I used the term in the "feeling" a boater has when experiencing the effects of prop wash.

In Aeronautical terms the fluid dynamics active when a prop is turning and moving air across the airplane body and tail is identified as:
Prop wash
A propeller pushes air not just horizontally to the back, but more in a twisting helix around the fuselage (clockwise as seen from the cockpit). As the air whirls around the fuselage it pushes against the left side of the vertical tail (assuming it is located above the propeller's axis), causing the plane to yaw to the left. The prop wash effect is at its greatest when the airflow is flowing more around the fuselage than along it, i.e., at high power and low airspeed, which is the situation when starting the takeoff run.

The prop on a boat acts similar when examining the fluid dynamics against the hull and the rudder.

After reading Peggie Halls message "If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein I am leaning towards less technical detail and more communicative terminology in an effort to communication. The walk or movement to port feeling you experience might resonate more easily.

Your thoughts?

jviss · Jul 18, 2018

None, really. Prop walk usually diminishes once you get up to speed, or run the engine fast; so not prop walk in this case. I suspect the prop isn't right, or it's too close to the rudder.

jssailem · Jul 18, 2018

Oh... Matt. Your post indicated you had joined today, but your response suggests you have been around since 2012... I apologize for my confusion.

Hard to tell why your boat was equipped with a 3 blade. In my experience most often it is to make the motoring smoother. 3 blades tend to vibrate less than 2 blades. 2 blades can be set to minimize drag improving your sailing speed - set prop to hide behind the keel when not in use. Folding props will enhance further your sailing speed yet at a little expense to your motoring and maintenance needs/costs.

I cruise in an area where I am as likely to be motoring as sailing. So I chose to balance the power considerations on my boat. I selected a 3 bladed CampbellSailor prop (the shiny one in the previous pictures). Design selection was discussed and provided by the manufacturer. I would lean to the manufactures guidelines. They will want to know the details of your engine, the transmission gear ratios, the shaft, and the number of bearings you have between the transmission and the prop. This is all about identifying the amount of power/torque your engine system is producing for the prop. Then it is a balancing function between size and pitch for the space you have between the prop and the hull. Too big a prop low pitch and the blades slices a hole in your hull. Too high pitch and small prop doesn't work either.

jviss · Jul 18, 2018

Great article on folding/feathering/fixed prop testing:
https://www.yachtingmonthly.com/gear/folding-and-feathering-propeller-test-29807

Interestingly, from the conclusions:

"If you want to add up to a knot to your boat speed, then fitting a folding or feathering propeller is a must, not just for racing boats. And as our test demonstrates, you can usually still retain the handling and performance under power that you had with a standard fixed-blade prop. In fact, often you’ll get better performance."

kappykaplan · Jul 18, 2018

jeepbluetj · Jul 18, 2018

I have a C-30, A4, Indigo Prop. Sure, it'll turn to port if you let go of the wheel for awhile, but it's nothing that me or the autopilot can't deal with. I get 6kts at 2000 RPM. (A4 - not the diesel) Most every other boat I've ever been on will turn too, so this is pretty much normal.

Something's wrong. I'd suspect the wrong prop.

Kingjim91 · Jul 18, 2018

I have a C30 with Atomic 4. The prop is 2 blade, 12X7. That’s the original spec.
Like jeepbluetj, I have a little pull to port, but not at all the struggle that Matt describes. Prop walk is more of a problem for me in reverse coming out from the slip. I have to counter-steer a little bit to port to come out straight.
Also, boat speed tops out at 6-6.5 knots at a little less than full throttle.
I know this is a different engine than you have, but I don’t think the issues are inherent in your boat. Like others, I suspect the prop.

Benny17441 · Jul 18, 2018

Mweimer said:
All good points. The more I think about my own symptoms, I suspect I have a bad or incorrect prop on the boat. A clean, fresh bottom and running gear made no difference. It does not happen under sail, and I am over revving and under speed.
So, if anyone knows what size Fixed props they have on the 25 universal that works great please share, a prop change will be my next step. Thanks!

I have seen those symptoms in boats that have the correct but fouled prop. Make sure the prop is clean of any marine growth before investing on a new one. One that is bent or out of balance could be repaired. When asking about what size prop others are using indicate that it is for a Catalina 30 as that engine mounted on a different boat could require a different size prop. The proper size for a prop is one that will allow the engine to reach its Maximum Rated RPM but not to exceed it. Check with other Catalina 30/Universl 25 owners to see what size prop they are using.

Kermit · Jul 19, 2018

Try swapping your front tires. That generally clears up any pulling in my steering wheel. The front left tire also might need air.
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Welcome to the forum!!

JamesG161 · Jul 19, 2018

Matt weimer said:
I thought this was a Catalina 30 forum! My apologies

Well, welcome to the "Forae"

And the helpers!!!

Kermit said:
Try swapping your front tires.

But alway in fun and sometimes informative.

Jim...

PS: My Hunter, with a 2 blade prop and full forward speed, maintains a hand free course in light seas.

Kermit · Jul 19, 2018

JamesG161 said:
...But alway in fun and sometimes informative.
Jim...

Emphasis on sometimes. Seriously, welcome to the forum. I’m *always* here to help... In my own way.