3 Blade Prop Swap?

jssailem · May 2, 2023

Lets start out with a Welcome to the SBO Forum.
Congrats on your new to you boat and the adventures you are planning.

Props are an essential element of the auxiliary system on your boat. The enthusiasm of this "A beautifully cared for boat" should some times be peppered with the recognition once you begin your journey the boat must be ready to get you safely to the end. Inspection of the prop, shaft, shaft log, stuffing box or dripless seal, coupling flange, transmission, and engine should be accomplished with an expert eye for the age and condition of the components. If you are new to this, please have a quality boat mechanic assist you at these first steps. Help with and observe what is being done, and why. We have all learned this stuff from others who shared their skills.

Your question was one I faced in the refitting my boat. I selected a Campbell Sailor 3 bladed prop from West by North. ( Home - West By North )They are located in British Columbia. It greatly improved my boat performance under auxiliary power and did not greatly reduce my sailing performance (when compared to no prop on the boat).

Here are the old and new. It is all about design, size and pitch to match your engine/transmission.

dmax · May 2, 2023

The 3 blade prop will improve your power significantly - I had a C-30 with a 3-blade prop and it motored well, really bites in when starting from a stop or reversing to slow down. You could feel the drag when sailing though, probably lost a 1/2 knot or more over a 2 blade. If you go the 3 blade route, I recommend getting a Campbell Sailer prop over standard 3 blades, much more efficient when sailing: Campbell Sailer

jviss · May 2, 2023

My advice is to not change anything that works until you have a year of use under your belt.

Ralph Johnstone · May 2, 2023

2 blade vs. 3 blade makes no difference in power if both are well adapted to their job. Neither one is rated for better efficiency over the other. The engine is operated at a cruising RPM of about 85% and that's your power output with both props.

jviss said:
My advice is to not change anything that works until you have a year of use under your belt.

It grieves me something terrible to agree with @jviss so readily

, but truer words were never spoken on the subject of props.

The only reason I changed from a 2 bladed to a 3 bladed prop was to get rid of the vibration of the 2 blades both aligning with the rudder slip stream at the same time. The new prop ran as smooth as silk after the change but nothing else other than the loss of maybe 0.5 Kts while sailing.

dlochner · May 2, 2023

Dudenhoeffer said:
1. This will be a long trek of about 10-12 days in canals and rivers and lakes, so perhaps an optimal cruising speed can be gained?

A three blade prop won't increase boat speed above hull speed, roughly 6 knots. A three blade prop will slow down the boat when sailing.

Now, about that long trip. Where are you starting? When do you plan to leave? Oswego to Waterford can be done in 4 days. To be sure they are long days. I've done it both ways from Fair Haven to Waterford and back in 4 days. There will be a little current on the Oswego River, but not that much and it is a relatively short canal, about 20 miles. Once past Sylvan Beach there is only one more uphill lock, the rest are all down hill and the current will be with you. The trip from Waterford to Lake Champlain is relatively short, but uphill, so there may be some current, I haven't done that section.

This time of year, most of the canal traffic will be north, you're headed south so the locks will be pretty empty, especially on week days. Wind in the locks is a bigger issue than current, in the locks there is no current. By the time you get out of Oswego (3 locks) you'll have the skills you need, by the time you get to Brewerton (lock 24) you'll be a pro.

shemandr · May 2, 2023

I agree it's better not to change the prop before a trip like this unless there is adequate time to test it. Matching diameter/pitch to a particular design of boat is something of an art. It definitely takes experience. You are a bit covered if Catalina Direct recommends a 3 bladed prop for your boat.

dlochner · May 2, 2023

Dudenhoeffer said:
We will set out from Rochester up to Oswego, which we hope to complete in 1 day... If all goes well, shooting to be queued up in Oswego for the day the canals open on May 19th. One unknown that I'm unsure how to time-budget for is the 33 Locks in the Route. I've got :30min per lock on avg as an estimate. Thoughts on this?

Love the enthusiasm. When and where will you take your mast down? Rochester to Oswego is a long long day. Figure at least 12 hours from dock to dock, if the weather is with you. Be prepared for cold weather, regardless of the forecast, the lake is currently about 45°, it won't be much warmer by May 19th. Consider stopping in Sodus Bay, roughly half way between Oswego and Rochester.

From Oswego you can easily get to Brewerton in one day. Then you have Oneida Lake. With a strong west wind Oneida can really kick up and be nasty. I lived on the lake for 10 years. Not something to do with a mast strapped down on the deck. If all goes well, from Brewerton you can make some where around Rome or Utica.

Estimating lock transit times is tough, too many variables. On the Oswego Canal the lock masters talk to each other, they will have the lock open when you get there unless there is opposing traffic. Further on, during opening week it could take longer, if your timing is unlucky. There will be a lot of traffic northbound, you may have to wait for that traffic to pass through the lock before you can pass through it. A lock can take anywhere from 20 minutes to over an hour. From Oswego to Waterford figure 4 to 5 days if all goes well.

If you haven't already, go to the Canal website and subscribe to the Notice to Mariners. That will give you the latest update on canal conditions and closures.

dlochner · May 2, 2023

Dudenhoeffer said:
@dlochner - Thanks for the insights. One question - We plan to step the mast before departing in Rochester. You mention Lake Oneida can get pretty choppy... and not something to do with the mast strapped on the deck. I haven't researched passage through Oswego to Lake Oneida with the mast up. Is that an option?

Once the mast is down, it stays down until you reach Lake Champlain. The controlling height for the canal is about 20' from Oswego and east, it is lower to the west.. There is good information on the canal website.

If the boat has the mast up now, I would leave it up until you get to Oswego and unstep it there. I am sure some have done the trip from Rochester to Oswego with the mast down, I wouldn't do that unless the mast was already down. With the mast up the boat is more stable and you will be less constrained by weather. There is a weather buoy near Rochester that reports conditions on the lake. Currently the water temp is 39° and the air temp is 39° with a S wind. Tracking the weather patterns for the next couple of weeks will prove to be informative.

NDBC - Station 45012 Recent Data

National Data Buoy Center - Recent observations from buoy 45012 (43.621N 77.401W) - EAST Lake Ontario - 20NM North Northeast of Rochester, NY.

www.ndbc.noaa.gov

Ward H · May 3, 2023

Welcome to SBO and Welcome to Catalina 30 ownership.
I agree with other posters about waiting to get time on the boat and learning about it's handling characteristics before making costly changes.
If you do want to investigate a 3 blade prop I strongly suggest you skip CD and work with a prop shop. CD has several props listed for various engines and transmission ratios but not an Atomic 4 30hp. I don't know if they run your specs through their computer and then have it pitched for your motor or they have a stock of various. And not all C30s are built the same so measurements from maybe a 83 C30 may not be the same as your 77. A good prop shop will need various mesaurements to ensure they recommend the correct size and pitch prop. While I like CD for many reasons I wouldn't trust getting the best prop for my boat from them. Also, their props carry a premium price tag. I have a quote from West By North which is about $250 less than CD.

As mentioned by @jssailem and @dmax, West By North is good shop to go with.

Sounds like you're planning a fun trip. Enjoy!

kappykaplan · Jun 3, 2023

Dudenhoeffer said:
good to know where the emergency tiller was!

Davidasailor26 · Jun 3, 2023

Sounds like a good trip. It could be worth checking the prop shaft alignment. At least that can be done in the water and it could explain vibration.

jssailem · Jun 4, 2023

When the water warms, you may want to dive under your boat and assure you did not pick up any debris as you transited the canals and rivers.

Shaft alignment (as David suggests)
Unbalanced prop (some one bit a chunk out of one blade)
Fishing Line/ rope / garbage bag on prop or shaft
worn cutlass bearing
loose shaft strut
Motor mounts worn

There is a quick list of possibles. Try the easiest first.

jviss · Sep 7, 2023

Dudenhoeffer said:
Hi @all - We have determined that the prop shaft is actually bent. There is a visible wobble at low RPM at the stuffing box. Couple newbie questions that I didn't find answers to searching around:
1. Is the original prop shaft material Bronze?
2. Our boat is on Lake Champlain VT, anyone know of a NE shop that I can work with to straighten then shaft?
Thanks for you insights!
Don

Straightening a prop shaft is something any competent machine shop should be able to handle. I'm assuming you're going to remove it yourself, or have the boatyard do so, and bring or ship it to have it repaired.

I imagine the boatyard would know local shops.

Failing that, I found these guys near me:

Fleet Propeller

jssailem · Sep 7, 2023

Dudenhoeffer said:
1. Is the original prop shaft material Bronze?
2. Our boat is on Lake Champlain VT, anyone know of a NE shop that I can work with to straighten then shaft?

1. Not likely. Steel alloy like Aquamet would be my guess. Certainly that is what you would be looking for to replace the shaft.
2. Bent shaft means you get a brand new straight shaft to replace it.

Here is one site that might be able to help.

New England’s marine driveline experts

H&H specializes in the customization and repair of all marine driveline components across recreational, commercial and government vessels.

www.hhprop.com

3 Blade Prop Swap?

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SBO Weather and Forecasting Forum Jim & John

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SBO Weather and Forecasting Forum Jim & John

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SBO Weather and Forecasting Forum Jim & John