Cavitation plate performance stabilizer. Are they of any value?

Bubbasboat

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I have a cavitation plate performance stabilizer I took off an Evinrude 115hp. Is there any value in my putting it on the Evinrude 70hp I now have on the boat? Do they really work?

Stabilizer.jpg
 

Frank Acampora

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Re: Cavitation plate performance stabilizer. Are they of any value?

Some people swear by them, some swear at them. The real answer is: Do you have a performance problem you are trying to correct? If not, then it probably will not give any benefit. It only takes four 1/4 inch holes to mount it so keep an open mind and try it. You can remove it in ten minutes.
 

ondarvr

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Re: Cavitation plate performance stabilizer. Are they of any value?

It's not a magic bullet that will make your boat faster or sexier, If you have an issue you wish to fix it "might" be of some benefit.

They aren't a bolt it on go boating item though, for it to work correctly (if it can help on your boat at all) you need to do some fiddling, adjusting and testing.
 

JimS123

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Re: Cavitation plate performance stabilizer. Are they of any value?

Best thing since sliced bread. I would'nt own a boat without one.
 

Bubbasboat

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Re: Cavitation plate performance stabilizer. Are they of any value?

I deleted this post as It is was an accidentaly duplicated post.
 
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Bubbasboat

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Re: Cavitation plate performance stabilizer. Are they of any value?

I believe the PO used the boat and 115hp on it for skiing. I have downsized to a 70 hp. Used primarily for fishing. I left it on the 115 until I took motor off the boat due to motor failure. I kept the stabilizer just in case???????? I know nothing at all about them, so must ask.

What will it do for me?

What kind of performance issue would I have that I would need one of these?
 

ondarvr

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Re: Cavitation plate performance stabilizer. Are they of any value?

There is a mistaken belief that the way to use one of these is to bolt it on and have it drag in the water to force the bow down or help prevent poroising, this is where the negative comments come from. They do sort of work when used in this fashion, but they can slow the boat down and possibly create some very odd, and possibly scary, handling.

A foil allows you to raise the motor higher on the transom without the prop ventilating (pulling air from the surface) under hard acceleration. The higher mounted motor can increase top speed due to less of the gearcase dragging in the water, plus possibly better MPG's for the same reason. It may also reduce bow rise and porpoising because the motor will have less leverage on the hull by being mounted higher. There is no guaranty any of these things will happen, and you will need to raise and lower the motor several times and record the results to know if it helped. It should definitely not be dragging in the water when on plane, this is what creates the issues people commonly complain about and then demonize the product for not working.
 

Sea Rider

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Re: Cavitation plate performance stabilizer. Are they of any value?

Foils are used too to plane faster a boat that uses much less HP than transom rated for and riding with not well ballanced boat. Is 70 the max that boat can handle ? Issues as : well engine/transom height seated, well propped, water conditions, load, trim will affect a boat to plane faster or not..

Foils besides slowing a bit a boat, are great collectors of unwanted plastic bags, kelp, even banana peels. Definitely not a fan of them.

Happy Boating
 

ondarvr

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Re: Cavitation plate performance stabilizer. Are they of any value?

Foils are used too to plane faster a boat that uses much less HP than transom rated for and riding with not well ballanced boat. Is 70 the max that boat can handle ? Issues as : well engine/transom height seated, well propped, water conditions, load, trim will affect a boat to plane faster or not..

Foils besides slowing a bit a boat, are great collectors of unwanted plastic bags, kelp, even banana peels. Definitely not a fan of them.

Happy Boating

Again, the incorrect use of a foil described above.
 

Sea Rider

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Re: Cavitation plate performance stabilizer. Are they of any value?

My post should have specified that that applies to medium size boats and portable engines with fixed clamp screws and mechanical trims in which you can't play raising engines that much as opposed to engines that sits and bolts to transom. Different animals. Again some swear by them, not me.

Happy Boating
 
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Bubbasboat

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Re: Cavitation plate performance stabilizer. Are they of any value?

If I understand, for my purpose it is really an unnecessary addition to my boat. I am not overly worried about her being the prettiest girl at the ball, she's not! She does sport a stainless steel prop!:) High performance is not a necessary aspect of boating for me. I usually do slower acceleration as I run older equipment and see no reason to unnecessarily stress it! When I take people out on the boat, they usually want a comfortable smooth ride, not a drawer filler experience. Mostly I use boat for fishing and camping. My cavitation plate is inline with my keel, as was recommended by many here on iboats when I mounted the engine a couple weeks ago. What you say about the effects of it dragging in the water makes perfect sense and the possible steering effects of being mounted that way. I think I'll leave it off, at least for now. I'm water ready, just waiting for the weather to be ready!:D

There is a mistaken belief that the way to use one of these is to bolt it on and have it drag in the water to force the bow down or help prevent poroising, this is where the negative comments come from. They do sort of work when used in this fashion, but they can slow the boat down and possibly create some very odd, and possibly scary, handling.

A foil allows you to raise the motor higher on the transom without the prop ventilating (pulling air from the surface) under hard acceleration. The higher mounted motor can increase top speed due to less of the gearcase dragging in the water, plus possibly better MPG's for the same reason. It may also reduce bow rise and porpoising because the motor will have less leverage on the hull by being mounted higher. There is no guaranty any of these things will happen, and you will need to raise and lower the motor several times and record the results to know if it helped. It should definitely not be dragging in the water when on plane, this is what creates the issues people commonly complain about and then demonize the product for not working.
 

ondarvr

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Re: Cavitation plate performance stabilizer. Are they of any value?

My post should have specified that that applies to medium size boats and portable engines with fixed clamp screws and mechanical trims in which you can't play raising engines that much as opposed to engines that sits and bolts to transom. Different animals. Again some swear by them, not me.

Happy Boating

If you are relying on it to drag in the water then it is not being used correctly. In the past I've compared it to using a Crescent Wrench as a hammer, not the correct application, but you can still beat on something with it. Don't complain when it doesn't do a great job though.

Even a clamp on motor can be adjusted for height, and for best results it should be. A fin only allows for more adjustability in some cases.
 

Bubbasboat

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Re: Cavitation plate performance stabilizer. Are they of any value?

I'm not sure what you mean by mid sized boats, I have a 16.5' which I consider to be a smaller boat, larger than my 1956 FeatherCraft was!! My motor is bolted to the transom. I think I'm going to leave the stabilizer off for the time being as it seems unnecessary for my personal boating style. Also, my transom is rated for 105hp max. Being a 40 year old boat, in good shape, but none the less, a 40 year old boat, I went smaller hp, less stress!!

My post should have specified that that applies to medium size boats and portable engines with fixed clamp screws and mechanical trims in which you can't play raising engines that much as opposed to engines that sits and bolts to transom. Different animals. Again some swear by them, not me.

Happy Boating
 

ondarvr

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Re: Cavitation plate performance stabilizer. Are they of any value?

I'd probably leave it off too.

The AV plate should typically be above the lowest part of the transom, and depending on the exact setup and prop it can be 1" to 2" higher. A SS prop will normally let you mount it higher than an aluminum prop. In line with the bottom is an OK starting point, but raising it will possibly allow it to perform better, and that's at no cost $$$ to you.
 

Bubbasboat

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Re: Cavitation plate performance stabilizer. Are they of any value?

I will verify actual location of AV plate in relation to deepest point on keel tomorrow. Will adjust motor if necessary to get it right!!

I'd probably leave it off too.

The AV plate should typically be above the lowest part of the transom, and depending on the exact setup and prop it can be 1" to 2" higher. A SS prop will normally let you mount it higher than an aluminum prop. In line with the bottom is an OK starting point, but raising it will possibly allow it to perform better, and that's at no cost $$$ to you.
 
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Bubbasboat

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Re: Cavitation plate performance stabilizer. Are they of any value?

I'm actually trying to avoid the drag, I do understand the possible effects. Will adjust motor if necessary to get it right! I prefer to us a hammer for a hammer and a wrench for a wrench!

If you are relying on it to drag in the water then it is not being used correctly. In the past I've compared it to using a Crescent Wrench as a hammer, not the correct application, but you can still beat on something with it. Don't complain when it doesn't do a great job though.

Even a clamp on motor can be adjusted for height, and for best results it should be. A fin only allows for more adjustability in some cases.
 

MikDee

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Re: Cavitation plate performance stabilizer. Are they of any value?

IMO, Smart tabs are the best idea, they help to get you out of the hole easier, & faster, if needed. They also help stability at low speeds, & when sitting still.

Yrs ago I bought an 18.5ft Wellcraft Airslot bowrider with a 188hp Mercruiser -302 Ford motor, and I could not get it to plane till I hit 3000rpm! Then I was going too fast, there was no normal cruising speed. I picked up these cheap plastic rigid trim tabs, and it made a world of difference. I was able to get on plane at 2500rpm, and picked up a couple mph at WOT too!
 

JimS123

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Re: Cavitation plate performance stabilizer. Are they of any value?

I will verify actual location of AV plate in relation to deepest point on keel tomorrow. Will adjust motor if necessary to get it right!!

You don't just adjust the motor to some pre-determined position that someone told you about. It has to be positioned and re-positioned many times, data collected at each point and then the optimum position selected. That will give you the best hole shot, fuel economy and top speed. Then, if you have bow rise, put on the fin and eliminate it.

Or, if you are like 90% of the boaters (that don't care about optimizing or don't read the internet), just hang her on the transom and go fishing and don't worry about it.
 

Sea Rider

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Re: Cavitation plate performance stabilizer. Are they of any value?

Ondarv,

As per post, nobody is relying on dragging a fin on water Going back to doel fin theme, seems you don't think a doel fin will plane faster an underpowered OB boat ? It does as per several posted threads on Iboats forums. As said before, I'm not a fan of them, have used them in the past and removed them inmediately after when found out that if you move your weight, cargo, passengers forward applying full throttle on a boat that has a underpowered engine (Max 30% off) of its rated power, will plane faster, useless installing a doel fin. If you like boating with a underpowered OB tiller driven and sitting near transom as a Italian Gondolier and with planing dificulties, a doel fin will help to overcome this.

For nice water performance, standard boat must ride near paralell to water level, at least 75% of its hull touching water, engine at 90? deg when on plane and doel fin paralell to water surface or will experiment fin drag due to its angle of attack at which cuts water flow at speed specially with a under powered engine. A larger engine can compensate this drag issue with no problem, not even noticing it. The idea is to take out the max of its HP power a underpowered OB will deliver.

Bubbasboat, if that 70HP engine planes boat nicely provided that boat is well weight ballanced, well trimmed and engine siting at perfect height match, you don't need a doel fin specially for cruising at fast displacement speeds for confy passengers ride likeness.


Happy Boating
 
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airshot

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Re: Cavitation plate performance stabilizer. Are they of any value?

You probably will not need it, only one time did I find a use for them. I had a 14' alum boat with a 15 hp jonnyrude, as I was sitting in the back all the time I made my own fin from SS. I am a toolmaker so these types of things are easy for me. The fin was a great way to get the bow down quickly to get on plane much faster with just me in the boat. I have had many larger boats with bigger motors and have experimented with them many times, the only time the fin was usefull was on the 14' that had most of the weight in the back, otherwise it was a waste of time if your boat is loaded correctly.
 
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