cavitation plate to keel on zodiac GR

[nice-diver]

hi
I have a 1997 Zodiac mk3 GR
It used to have a jet drive on it that used a raised...laminated transom plate.

When the long shaft johnson 40 was installed the cavitation plate measures two inches above the bottom edge of the transom.

my problem: if the boat gets on a plane it cavitates and looses bite. the prop moves water, but not the boat.

my question: what is the measurement difference between the lower transom edge and the lower edge of the cavitation plate.

I will trim the aluminum laminated plate shorter to lower the motor to the proper height

thank you

 

[NYGiants]

Re: cavitation plate to keel on zodiac GR

you want the top of the cavitation plate equal with the bottom of the transom

 

[nice-diver]

Re: cavitation plate to keel on zodiac GR

what happens if i drop it too low?

 

[deejaycee_2000]

Re: cavitation plate to keel on zodiac GR

nothing will happen really will just be a little unstable on high speed .... but with such a small boat you will hardly notice it ...

 

[NYGiants]

Re: cavitation plate to keel on zodiac GR

i ran an extra long shaft motor on my rowboat which is made for a short shaft.
it planed and everythin g(8hp, 12ft skiff) but created a monstorus wake, and unstable at turning. Keep in mind the motor had an extra ten inches of water.
a few inches will be fine

 

[nice-diver]

Re: cavitation plate to keel on zodiac GR

thank you

I was told too deep will cause it to spray water

I am off to do some cutting

thank you

I will try post pics here soon

 

[Gravity Matters]

Re: cavitation plate to keel on zodiac GR

I am currently doing the same with a 1997 Zodiac Futura Mak 3. I have a 60hp Mercury 2stroke. With the cavitation plate even with the bottom of the keel/transom I could not get going on the speed tubes without it ventilating. With the boat loaded up (5 people it wouldn't ventilate but with just 2 (larger) people I constantly wash ventilating.

I just lowerd the motor 1" below the keel/transom as reccommended by a dealer with some knowledge. I am going to try it in the next couple of days.

 

[nice-diver]

Re: cavitation plate to keel on zodiac GR

its hard to get an answer, I am lucky mine is a simple hull with the tubes about even with the transom. friday night is my test date.

"thats my booat" me said in my best Forest Gump voice

 

[Gravity Matters]

Re: cavitation plate to keel on zodiac GR

Well got the boat in the water last night and gave it a try. Lake was very calm, 3 people in boat and all gear. I had lowered the transom (converted short to long) by 2 1/2 inches to get the motor down as stated above 1" below transom. This worked well in almost all repects. boat handled well, out of the hole acceleration was amazing (though it is a 60), while on plane loaded there was no ventalation. While pulling a tuber behind it worked well out of the hole and at full speed in most turns without much ventalation.

I went out alone to see the effects but was running out of time near dusk. out of the hole fast!! I could make it ventalate a bit, but didn't have aenough time yet to play with trim and weight distribution.

The only big difference I noticed was spray at the back, I may be a tad too low but will have to check this out on another trial.