Cavitation plate ... Does size matter?

[Lakeshadow]

The 33 pony Ski-Twin (blue), doesn't have much of a cavitation plate on it. Yet the 40 pony Selectric (white), has more of a cavitation plate on it.

The Ski-Twin is more of a base sticker model that comes with a recoil and electric starter yet no generator. I am supposing the top of the line outboard has more of a "fin" on it just because it's top of the line, and the extra bit of fin gives the 40 a bit more action. The 40 pony Evinrudes with standard shift have the same cavitation plate.

I think I'll mock up a design or two that is just a bit more than the factory offered on the 40's. Maybe only an inch or so wider on each side and a couple inches longer? I don't know yet, tossing the idea around in my head for now.....

 

[aspeck]

Re: Cavitation plate ... Does size matter?

There, lakeshadow, instead of hi-jacking an old thread, I started a new one for you ...

 

[phillnjack2]

Re: Cavitation plate ... Does size matter?

Look how nice and sharp the white bullet is.
looks more like a very modern low water pick up style with a nose cone.
funny how the old ones come back into fashion decades later.

phill

 

[jimmbo]

Re: Cavitation plate ... Does size matter?

Both designs are over 50 years old. A long way from Modern gearcase design

 

[Lakeshadow]

Re: Cavitation plate ... Does size matter?

[h=2]Thread Hijacking[/h] Thread hijacking is the process of replying to an existing thread with a different topic. This is generally discouraged. It is better to start a new thread if you have a problem that is related to an existing posted issue but clearly different. Posts that hijack a serious thread with off-topic discussion are also discouraged.

So this is hijacking.

 

[Lakeshadow]

Re: Cavitation plate ... Does size matter?

I know one thing for sure.... The same old boys that were saying to me "That's a whole lot of outboard to be pull starting", will have something to say about a home made hydrofoil.

Think I know how I'll start the design. I'll make it fit the bolt pattern on the 40 white bullet cavitation plate, then transfer it over to the 33 since I'm using the 33 now.

I can't help it...... I'm a sheenie man.... oh boy...


Steady as she goes.....

 

[UncleWillie]

Re: Cavitation plate ... Does size matter?

The plate is actually called an Anti-Ventilation (AV) Plate.
Its purpose is to prevent the propeller from sucking in air from the waters surface and Ventilating the propeller.
Cavitation is something entirely different.

If the Prop is not ventilating as it is, what is the purpose of enlarging the plate and producing more drag?

 

[phillnjack2]

Re: Cavitation plate ... Does size matter?

I was merely pointing out the shape of the bullet of the white gearcase !!!
it is very similar to what is now considered high performance nosecone. ha ha
the shape of the bullet not the whole gearcase.

if either engine was mine I would put a plate on only if I was getting A too much spray, or B too much cavitation due to ventilation.

is there any problem that is arising with either gearbox at present when running ?

phill

 

[Mel Taylor]

Re: Cavitation plate ... Does size matter?

I can't help it...... I'm a sheenie man.... oh boy........

What, pray tell, is a sheenie man?

 

[Lakeshadow]

Re: Cavitation plate ... Does size matter?

Hi UncleWillie, I keep reading how a hydrofoil can help a boat stay on plane at a lower speed than without it. This is what I'm thinking since this is a smaller boat with no power tilt or trim. I don't want to install a full size hydrofoil like I'm seeing available. I would like to make one smaller and see how it goes.

Phil, ha. Working on the compass drawer today I keep calling the 40 the White Bullet to myself..... The name has stuck. Well, there's a little bit of spray with the 33 but I still want to see if I can get a plane at lower speed. I haven't run the White Bullet yet! Going to go at that outboard later after I move.

Hi Mel, My buddies dad always called me a sheenie man, I think it means like a junk collector or junk rigger upper. I was always screwing around with stuff I found. Couldn't leave any of those cheap old cars I drove alone. Me and my pal Dale still call each other a sheenie man from time to time.

 

[jimmbo]

Re: Cavitation plate ... Does size matter?

The bolt patterns for the case to midsections are the same. That alone may not make it swappable. Water pumps will be different as the 40 will have a recirculating system. Also, the 40 gearcase is an electric shift while the 33 is a mechanical shift. That alone makes the swap extremely difficult if not almost impossible. As for the cool pointy nosecone... It was not a very good gearcase design but it does snag weeds and other trash very well

 

[Lakeshadow]

Re: Cavitation plate ... Does size matter?

Jimmbo, hold on here. I made no mention of a swap of parts from one outboard to another. My boat is now wired for standard shift and selectric shift. The selectric outboard is on the back burner for now.

I own service manuals for the Ski-Twin and White Bullet, in fact the wiring I used to wire Miss Peachtree is the wiring harness that came with the 40 pony selectric, so the wires were there to fall into place. And I used a junction box for a 65 with a charging system, fabricated, incorporated on the transom. Therefore I charge my battery at the junction box if desired, while I'm amusing myself turning rheostat switches and watching lights go dim and bright... hehehe..

I am well aware of the top of the line differences and goodies on the White Bullet like a thermostat etc. Eventually I would like to polish all the alloy on the 40 and repaint the cowl. The stainless trim on it is in beautiful condition.

Steady as she goes......

 

[jimmbo]

Re: Cavitation plate ... Does size matter?

Sorry, I glanced at one posting that mentioned Bolt pattern and, not reading through, jumped to the wrong conclusion(now that I have one foot in my mouth I wonder how long till it will be before I have to change feet?)
Good luck on whatever you do with it. My dad owned a 40 with the electric shift and an old 35hp(for all purposes the 33 is the exact same engine). The 40 was faster out of the hole, but I feel that was due to more torque from the larger displacement, not from the anti-ventilation plate. I really liked the electric shift, never gave any trouble. On the 40 that is. On our 90hp, the electric shift was a real Pain in the Caboose.

 

[Lakeshadow]

Re: Cavitation plate ... Does size matter?

No biggie Jimmbo, ha.... That electric shift sure seems decent to me. The throttle lever ratchets like cruise control and the idle adjustment is right there at the control box. I am hijacking myself.... 'oh no..... The Sierra lower lube states it can be used on all outdrives. The man Ron at Valley Sales in Prudenville tells me to only use 10w30 in electric shift units or it will fail. There is a topic I got to get on. Time to search Selectric threads.

I think I see how a hijack can disrupt. Seems the search function can bring back too much clutter if threads are not topic specific. ? ...

The bolt pattern is, seems someone has already had a hydrofoil bolted to the 40.

Just to add there is a 100 Starflite selectric with wood grain and stainless trim, too much for my boat unless I was racing, but it sure looks cool. For sale in Plymouth for 600 bucks, too much for me. Where would I get a super pitch prop for it anyway..... Another thought,,,,, wondering what the weight difference is between a 60-65 and 100 pony old four banger???

See ya later....

Steady as she goes......