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Well-known member
Supporting Member
Feb 24, 2006
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Solomons Island, MD
Ok...since there was a discussion about these things, here are pics of the "Cobra Marine" plates I use.


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I used to have to run the motors trimmed all the way down, and the tabs in the full down position to get a half-decent ride. Once the plates were added, and the motors in the neutral position, the tabs are much more sensitive. I rarely have to use them, but when I do, it really makes a difference. I also get much better fuel economy because the motors are more neutral and the tabs aren't plowing the water.

The upward pressure on the plates in the neutral position is sufficient to overcome the weight of twin 4-strokes.
Well here's another question. My boat doesn't run "in the zone" unless the motor is tucked tight to the transome. I never trim the motor at all, in fact. What's everyone else's SOP?

On my Bass Boat I use the motor trim constantly to keep the prop vortex aligned, but with that boat there is only a very small footprint of hull in/on the water at speed as opposed to the semi-displacement/semi-planing hulls that we have.
rangerdog":2d94ap6d said:
Well here's another question. My boat doesn't run "in the zone" unless the motor is tucked tight to the transome. I never trim the motor at all, in fact. What's everyone else's SOP?...

What do you mean "in the zone?" Do you mean neutral (anti-ventilation plate parallel to the keel)?
Did these plates take away any top speed? How much do you think they lowered the bow?

I have twenty 5 pound lead bars in my anchor locker that seemed to lower the bow angle about 4 degrees and reduce my time to plane by about a second. Think I would still need the lead bars or am I getting about the best I can get now?

I have a 2120 DV SC with F150 four stroke. Running in calm water with a full load of fuel (or a half load) get 39-40 MPH at 5700 RPM burnig 17 GPH.
I run a 2520Xl with 225 four on it. I put on the Permatrim and noticed greater response from the trim tabs (which, for me, negates the whole argument that Parker's factory tabs are too smal), better performance in terms of hole-shot and top end. Also, the boat corners better without ventilating the prop. I don't have super-accurate numbers, but I estimate upon observation that the boat is 1-2 mph faster at top end, same rpm; cruises better/faster (due to better running angle/trim set-up); and holds plane at lower speed (formerly dropped off around 18, now goes as low as 14 or so, depending on trim, water conditions). Installation wasn't too much fun due to limited instructions, template, but I'm happy with what it seems to have done for the boat.
Adding weight is not the right solution. Moving existing weight forward and/or adding surface area to trim surfaces is.

Adding the two Cobra plates gets me onto plane quicker and I can now stay on plane down to about 14 mph. Before the plates, at WOT I often tickled 40 mph at 5,600 rpm. After the plates, I rarely tickle 40 mph at a WOT rpm of 5,600. So...maybe I lost an average of .5 to 1.0 mph. Fuel consumption dropped about .2 gph at cruise on a nice day, but increased by 2.0 gph in snotty seas because the motors are not trimmed all the way in and the tabs all the way down (effectively plowing lots of water).

All in all, well worth the cost. They are cheap too...about $65 a plate vs $400-500 and a lot of work to change out the Lenco tabs for larger Bennett tabs.
Thanks for the input and the pics porkchunker.
Appears that the plates are the way to go.
I also have experienced cavitation during what I consider to be cautious turns at reasonable speeds. I can't swear as to what trim position I would have had the motors in at any given time but very seldom do I run at speeds and distances that call for that refinement.
Since I am a charter and bow riding is verboten I generally have up to six adults in the back third of he boat and eight in the back half.
She is quick to drop off plane. In my case the fluctuating passenger weight causes a wide range of fuel consumption and SOL and RPM readings at the moment planeing occurs or when I drop off plane. Hopefully the plates will help with that problem also.
Have a great day on the water!

Skipper Hub
After running the plastic fin on top of the cavitaion plate and then the Cobra plate that bolted on the bottom of the cavitaion plate, I would prefer the Cobra bolted to the bottom as it performed better for me and it pushes up on the cavitaion plate so would probably not break it.

Bottom line for me was I removed the plate and finally found the right prop for my 150 4s and the boat performance was better all around. Then I bought 12X18 Lenco trim tabs and replaced the 12X12s that came on the boat new. Big change in easily trimming the boat as people move around the stern with these larger tabs.

I did not move the Lenco trim rams so there is 6 inches of trim tab outboard of the trim ram and 12 inches of the tab inboard. Made the installation very simple, never removed the rams - just had to remove the old 12X12s and then drill three holes on the trim tabs to attach the trim rams to the new tabs.

Will get some photos is anyone interested...................Pete
I see a product called a PERMATRIM manufactured in Australia. The mfg claims they are the original with a pic of the inventor etc.
The application is the same as the cobra. The plate mounts on top of the cavitation plate instead of on the bottom.
It is suppose to provide the same function.
It is shaped differently. It has a turned down edge of about an inch on both sides and is generally more straight front to back.
They mount with ten bolts, five to a side as opposed to the cobra mounting with six I think.
They are also expensive. They start at $80 and go up.
You can google them on the web.
Anybody familiar with them?

Skipper Hub
Here is shot of Lazyman Lenco Upgrade. Left the ram where is was with the factory 12X12s and installed the new 12X18s with 6 inches outboard (same as old ones) and 12 inches inboard. I did put in a stainless angle to help carry the load to the unbalanced side but doubt I needed it. Just had to patch the holes Lenco put in the tabs and drill new holes for the ram to attach to the 12X18s.

Will make a separate post on this, but it is really starightforward. Boat runs super and the tabs work great. I got a set of rams with the new tabs for virtually no extra cost so now have two spare rams............Pete


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How do I treat the holes in the hull where the trim tab attaches.
Is that a cored area? Thru hull? Will 5600 do it ? Do I need to fill holes and refinish fiberglass surface before mounting the new tabs?
Last but not least, am I making a mountain out of a mole hill?
I just get little queasy when I start drilling holes in my hull even if its up on the gunnel.

Thanks for the input.
I paticularly like the part about the cost of a tab from West Marine being $110 or there abouts. I was getting numbers of hundreds per unit. I guess that must have included installation.
Now I am wondering if Bennet tabs cost more and are worth more or what. They have a strong following of satisfied customers.

Skipper Hub