Cavitation plate

[Funkyfarmer]

Hi,<br />This is a great site. I have found out things about my motor in one day that I have spent many weeks of emailing ect to no avail! Thank you those concerned.<br /> I have bought a boat, trailer and engine off of ebay for the princely sum of £200 ($340ish) It is a project for the winter while life on the farm is quiet. She is a 16ft cathedral hulled cabin boat. Don't ask the make or year, suffice to say she was Noah's rescue boat I think. Anyway I intend turning her into an open fishing boat with a small cuddy. Pictures will follow as and when I get around to it.<br />OK. Enough of the boring stuff! My question today is: The outboard that came with the boat is a Merc long shaft. When attached to the transom the cavitation plate is 2 1/2 inches below the line of the keel after raising it by 2 inches. I don't want to raise it any further as it will mean a lot of extra strengthening ect. What are the likely concequences of not lifting the motor? If any.

 

[phantoms]

Re: Cavitation plate

Get a jack plate and you can put the motor where you want it and then adjust for best performance.

 

[Solittle]

Re: Cavitation plate

If top performance is not all that important run it like it is. I run a 9.9 long shaft on a 12' tinny with no problems.

 

[Funkyfarmer]

Re: Cavitation plate

Thanx Guys.<br />Ahem!!!! Wots a Jack Plate?

 

[phantoms]

Re: Cavitation plate

Iboats Jack Plates.

 

[mjbrueck]

Re: Cavitation plate

If it's a displacement hull or run at displacement speed, put the motor back down to where it originally was. If it's a planing hull, you'll need to raise it above the keel for best performance. With our "cheap" $3 gas, us Americans assume all boats are planing boats.

 

[danie]

Re: Cavitation plate

FF, for the sake of correctness, its called an anti ventilation plate, not cavitation plate.<br />D

 

[Funkyfarmer]

Re: Cavitation plate

Well! That told me Damdan! I bow my head in shame LOL<br />You got that right MJ I have just filled a new tank with 5 imp gallons of 2 stroke petrol Cost me £25 about $40 US. Don't you just love it?<br />Cheers<br />Funky

 

[Funkyfarmer]

Re: Cavitation plate

Thanx for the link Phantoms<br />If anyone can email me the dimentions of a jack I will make one myself. The look a bit pricey to me for what they are?<br />Cheers<br />Funky

 

[KIGuy52]

Re: Cavitation plate

How big is your motor? I raised my 25hp long-shaft by simply bolting a strong 2x12 board to the transom. All the old salty sea-dogs cringe, but it works fine.<br />By the way, I've always called it an "anti-cavitation" plate too. This link confirms that it's ok.<br /> http://www.fiberglassics.com/terms/

 

[ob15]

Re: Cavitation plate

that webpage is incorrect. If you look at cavatation on the same page you would be totally confused. It's a good definition for chine though. It is called an anti-ventilation plate. Ventilation accours when air mixes with the water around the propeller and the prop slips. Cavatation is a totally different animal and is cause by other things.

 

[KIGuy52]

Re: Cavitation plate

Probobly just a typo. The writer's definition of "chine" is the same. To avoid confusion in the future, I'm going to refer to it as the plate thingy over the prop thingy.

 

[TIM GRADIE]

Re: Cavitation plate

WHERE DO I MOUNT MY MOTORS? <br />I HAVE TWO 150HP JOHNSON OCEAN RUNNERS 1995 MODELS. HJ150NXEOM. SERIAL NO G03793333AND 03832887 RESPECTIVELY.I HAVE A 25 FT CAPE CRAFT AND I HAD AN OLD OUTMOUNT BRACKET ON MY BOAT WITH THESE MOTRS MOUNTED ON THE OUTMOUNT. I COULD NOT GET MORE THAN 4200RPM OUT OF THE MOTORS ,SO I FITTED A 15 INCH FOUR BLADE PROP TO EACH MOTOR.THIS STILL DID NOT IMPROVE MY LOW REVS .IVE BEEN TOLD MY MOTORS ARE LYING TO DEEP IN THE WATER.I THEN REMOVED THE OLD OUTMOUNTS, THIS OUTMOUNT WEIGHED MORE THAN ONE MOTOR.I HAVE HAD NEW OUTMOUNTS MADE AND AM NOW WANTING TO KNOW AT WHAT HEIGHT TO MOUNT THESE MOTORS TO GET OPTIMAL PERFORMANCE

 

[danie]

Re: Cavitation plate

No no Timmy, you will not get a response by hijacking someone elses thread.<br />Go back to the forum topics and read JB's comments, New posters: Read this first.<br />D