cavitation plate issue

[Selles]

I have Mariner 25hp ,the cavitation plate is 3inches above of the bottom of the boat,that distance make cavitation problem or not? <br />15"leg

 

[catfish1]

Re: cavitation plate issue

try it out & see. if it cavitates, then lower the motor. its all trial & error! because every hull is different.

 

[Solittle]

Re: cavitation plate issue

I think that you will find that the motor is set about 3" too high. The starting point for a good set up is where the cavitation plate is even with the bottom of the hull.

 

[OBJ]

Re: cavitation plate issue

Yep...what solittle said. "General Rule of Thumb", Cavitation plate no more than an inch below or above the keel of the boat.

 

[Hawaiian]

Re: cavitation plate issue

It is called an ANTI-VENTILATION plate. It prevents the prop from ventilating not cavitating. It should be even with or an inch or two above the bottom of the hull depending on your hull, prop etc.

 

[walleyehed]

Re: cavitation plate issue

Easy Perry, even the manufacturer calls it a cavitation plate!!!!!<br /> We understand cavitation is low pressure boiling of the water on the face of blades and vetilation is when air is INDUCED to the prop stream, and causes a rise in RPM. Regaurdless, it's commonly known as the cavitation plate.........

 

[Hawaiian]

Re: cavitation plate issue

Walley, which manufacturer are you refering to? In both my Honda manual and my old Mercury manual, it is referred as a anti-ventilation plate. If the plate prevents the prop from ventilating, why would it be commonly known as a cavitation plate?

 

[AUGIDAWG]

Re: cavitation plate issue

(I found this on the web. Note where it says "air ingestion". So, an "anti-ventalation" plate would help prevent cavitaion, so you could refer to it as a "anti-cavitation" plate)<br /><br />SUBJECT : Cavitation 1-3<br /><br />Cavitation means that cavities are forming in the liquid that we are pumping. When these cavities form at the suction of the pump several things happen all at once.<br /><br />We experience a loss in capacity. <br />We can no longer build the same head (pressure) <br />The efficiency drops. <br />The cavities or bubbles will collapse when they pass into the higher regions of pressure causing noise, vibration, and damage to many of the components. <br />The cavities form for five basic reasons and it is common practice to lump all of them into the general classification of cavitation. This is an error because we will learn that to correct each of these conditions we must understand why they occur and how to fix them. Here they are in no particular order :<br /><br />Vaporization <br />Air ingestion <br />Internal recirculation <br />Flow turbulence <br />The Vane Passing Syndrome

 

[BillP]

Re: cavitation plate issue

Long before Honda was around outboard mfgs and mechanics called them cavitation plates. Whatever you choose to call it the prop is churning air and the fix is generally the same...lower the motor or drop the prop pitch. For drag reduction setting the cavitation plate about 1/4"-1/2" above the bottom is a good place to start but not below it.

 

[walleyehed]

Re: cavitation plate issue

Perry, Honda is "new" to the outboard market compared to J/E, Merc.<br /> Don't care what Honda, or anyone else calls it, it is (was) commonly known as the cavitation plate.<br /> My OEM manual for my 83' 70hp Merc says "cavitation plate".........call it what you want, I guess.........doesn't matter, we all know what it is, or atleast where it's located..........

 

[OBJ]

Re: cavitation plate issue

Selles, ya' ought to by now have a good idea of where to put the anit-ventilation-cavitation-keep the air-outta tha prop thingy.<br /><br />Gee....hope I said that right.

 

[walleyehed]

Re: cavitation plate issue

^5, OBJ!!!!!

 

[Hawaiian]

Re: cavitation plate issue

augidawg, the definitation you posted refers to a sealed water pump like the one in the fire truck I drive at work. Cavitation in a water pump occurs when low pressure boils off the water on the edge of the impellor. When surface air is introduced to a propellor on a boat, it is called ventilation. And what prevents this from occuring? A anti-ventilation plate. I've been boating for over 30 years and maybe it is just here in the middle of the Pacific where we refer to them as anti-ventilation plates. I didn't mean to stir up the pot. Call them what you wish.<br />Aloha...

 

[rickdb1boat]

Re: cavitation plate issue

An anti-ventilation plate does not nessesarily prevent Ventilation. Motor set-up, transom design and lower unit depth in the water are more likely to stop or reduce ventilation than a small plate. Just my .02. And yes, here in the midwest, we call them cavitation plates.

 

[BillP]

Re: cavitation plate issue

Perry,<br />FYI...cavitation is taught and printed as "disturbed water around the prop". It doesn't matter how it gets disturbed. Venting is one factor. At least that is what they taught me in school (Merchant Marines and USCG). <br /><br />I hold merchant marine docs issued by the DOT/USCG and did the schooling thing.<br />#Z-1289463<br />A1946611

 

[Selles]

Re: cavitation plate issue

THANKS FOR YOUR HELP GUYS

 

[Selles]

Re: cavitation plate issue

I THINK MOVE DOWN MOTOR EVEN HULL WITH A BRACKET IS GOOD IDEA?

 

[Hooty]

Re: cavitation plate issue

I thought it was a step for climbing back into the boat.<br /><br />c/6<br />Hooty

 

[Bowhunter555]

Re: cavitation plate issue

Can't we all just get along!!!<br /><br />"Anti-Cavilation Plate"

 

[ob]

Re: cavitation plate issue

The prop ventilates from air cavities just below the step for climbing back into the boat