Cav 32 Prop details

[Cavalier 32]

Hi All,

I have a Cavalier 32 that requires a new prop. Challenge is that it has a full rudder and the prop is in an aperture which limits the prop size. The one fitted gives me about 4 knots tops!!.

When I went to remove the old prop (underwater) I found that there isn't enough room to get the prop off the shaft. It hits the leading edge of the rudder. Is this a normal occurrence? Surely I don
t need to move the engine and gearbox just to get the prop off.

Any suggestions. The calculations call for a 17" prop. but that is way to big for the apperture. Bit of a design limitation I am afraid.

Any ideas.

[Wanderlust]

I had a Cavalier 975 (same hull) with a Bukh 20hp. It had a 15x11 3 blade fixed prop and it seemd to be the ideal size. If your engine size is larger then a larger prop would be justified. I also had a 2 blade but found it lacking in torque, so preferred to put up with a little extra drag when sailing.

The space behind the prop is fairly tight, but should not be an issue with removal.

I suggest you check that:

• the prop shaft is fully forward in the drive collar
• the propeller boss is close to the shaft housing
• there is minimal (wasted) thread protruding behind the prop.

[Cavalier 32]

Thanks for that. I was thinking of going to s 3 blade to compensste for the smaller diameter. I think i have 3 to 5 threads still protruding so i hope that will be the difference if i lop them off (easier said than done). Can you tecall your prop supplier and details?
Keith

[Wanderlust]

I didn't buy them ... they came with the boat. The 3 blade was a Porter. Sorry, don't recall the 2 blade one.

I remember the 3 blade prop was a bit damaged when the shaft key sheared, and it rattled around loose for a while. I sent it to Porter for repairs. They suggested using my spare prop to make a plaster cast of the taper and keyway. They could then be sure the repaired prop would be a snug fit. I then fitted the spare prop so the boat could be launched again rather than wait for the repair.

That technique may be helpful for you when shopping for a replacement.

[Cadence]

Originally Posted by Cavalier 32

Hi All,

I have a Cavalier 32 that requires a new prop. Challenge is that it has a full rudder and the prop is in an aperture which limits the prop size. The one fitted gives me about 4 knots tops!!.

When I went to remove the old prop (underwater) I found that there isn't enough room to get the prop off the shaft. It hits the leading edge of the rudder. Is this a normal occurrence? Surely I don
t need to move the engine and gearbox just to get the prop off.

Any suggestions. The calculations call for a 17" prop. but that is way to big for the apperture. Bit of a design limitation I am afraid.

Any ideas.

What about positioning the helm hard over. Had you tried that to gain possibly just enough clearance. The leading edge may be a little closer the prop shaft than the side of the rudder shaft?

[Bill Conlyn]

As the pre person said moving the rudder both ways may allow the prop to slip by the end of the shaft. Some material could be removed from the leading edge of the rudder. Also I have removed some of the hub material from the back end of the prop with no detrimental effects. Also u will be better off with a 3 blade MP round bladed prop and will not ever notice any drag under sail despite what the engineers say. MP stands for machine pitch it is just as effective in reverse as it it is in foreward which is a big help in maneuvering. As he said make sure the shaft is all the way in the coupling and is properly dimpled.

[Jim Cate]

Also u will be better off with a 3 blade MP round bladed prop and will not ever notice any drag under sail despite what the engineers say.

I wonder if you are a member of t he flat earth society.... those guys don't believe what engineers or other scientists say either.

(That was an attempt to provide a slightly humorous rebuttal to your claim that three blade props do not add perceptible drag when sailing.)

Many sailors, myself included have done the experiment of changing away from big three blade fixed props and have indeed found very noticeable improvement in sailing performance.

Jim

[Cadence]

Something sticks in my mind, that some people would lock a two bladed prop vertically behind a full keel to minimize drag.

[Cavalier 32]

Thanks Steve,

Any problem with the aperture. It seems awful close. Right now though I have 3.5 knots full ahead and next to no astern at all. Anything would be better than that. What kind of speed are you getting now, and astern??

Cheers

Keith

[Wanderlust]

I was hoping a present Cavalier owner would chime in here.

I haven't had that boat for several years and my memory on the specific speeds and revs is a bit hazy. But it certainly did much better than 3.5 knots, maybe close to double that. I never thought of it as being slow under power. Reversing power was less, particularly with the 2 blade, but far from non existent as you describe.

You haven't said what engine you have, whether it achieves maximum revs in gear or why the the prop needs replacing.

If you have a 20hp engine, as was common for this model, it should achieve more than 6 knots.

Check if the prop is clean and not damaged. A prop with heavy growth will severely limit the ability to achieve maxium revs. If it's simply oversized, the engine will not be able to reach full revs, thus limiting your speed. If the engine is easily revving to maximum it indicates that the pitch on your prop is too fine.

Cadence suggested turning the rudder to assist removal. I do recollect doing that in conjunction with rotating the prop. If it went on, it must come off.

[Cavalier 32]

Hi Steve,

I ended up with a new Prop and a 3 blader. Looks massive compared to the old 2 blade. My problem is getting it on the shaft. I am doing so with her in the water. It doesn't look like the 3 blader will go anywhere near on the shaft. The rudder gets in the way of the 3rd blade. Can you recall fitting your 3 blade? Is it possible to get the rudder just at the right angle to get the prop on, or do you recall having to remove the rudder etc. (On the hard of course).

Cheers Keith

[Wanderlust]

I think it needed the rudder turned one way, then the prop rotated a bit and then it would slide fully home. The rudder definitely did not need removal.

I have attached a couple of photos that may help. For the 2 blade you can fairly clearly see the size of the prop and the gap to the rudder ..... not so easy for the 3 blade photo. Its hub size would have been close to the same size. I would not describe the 3 blade prop as looking huge.

Perhaps your shaft has moved aft a little.