Trim Tab Zincs

C

catfish54

New Member
Mar 29, 2016
13
Iowa Mississippi river
Boat Info
1998 270 Sundancer
Engines
7.4 MPI Mercruiser w/BravoIII drive
My trim tabs have a 3.75" dia. rudder zinc on top of trim tab. I ordered two rudder zincs to replace them well they come in pairs could I put one on bottom and one on top of trim tabs without affecting the use of the trim tabs. Boat is 1998 Sun Dancer 270 7.4 MPI Bravo3. thanks Leon
 
catfish54 said:
My trim tabs have a 3.75" dia. rudder zinc on top of trim tab. I ordered two rudder zincs to replace them well they come in pairs could I put one on bottom and one on top of trim tabs without affecting the use of the trim tabs. Boat is 1998 Sun Dancer 270 7.4 MPI Bravo3. thanks Leon
Click to expand...
Mine are top and bottom. Been that way since I bought the boat. All my marina mates have them this way as well.
 
If you do not order them correctly, they come set up for rudders which go on both sides. Since many folks don't know to ask, they get them this way and install both pieces on one tab. If you order them specifically for trim tabs, there is a nut pressed in both halves and two screws to install just on top.
 
I have always installed rudder anodes on my tabs. So one in top one on bottom. If you only had one and now will have both make sure the tab is sanded with no paint where the anode makes contact.

-Kevin
 
paulswagelock said:
If you do not order them correctly, they come set up for rudders which go on both sides. Since many folks don't know to ask, they get them this way and install both pieces on one tab. If you order them specifically for trim tabs, there is a nut pressed in both halves and two screws to install just on top.
Click to expand...
Didn't know that. I've just been tapping (more like pounding with a hammer) a nut into that second anode. Also their 1.5" long bolt is way too long for just one side. I bought a couple 3/4" long of the exact type from local hardware store and use those.
 
I have a 2000 Sea Ray 270 DA, and mine are only on the top with a stainless screw coming up through the bottom, FWIW if you’re in freshwater you don’t even need them because they are stainless steel
 
FWIW Bennett recommends installing the Zinc on the top surface of the tab only. Having a Zinc on the bottom interrupts the flow of water over the bottom surface of the tab and therefore reducing it's effectiveness.
 
catfish54 said:
My trim tabs have a 3.75" dia. rudder zinc on top of trim tab. I ordered two rudder zincs to replace them well they come in pairs could I put one on bottom and one on top of trim tabs without affecting the use of the trim tabs. Boat is 1998 Sun Dancer 270 7.4 MPI Bravo3. thanks Leon
Click to expand...
The zincs are profiled slick enough so I doubt they would effect performance on both sides of the tab. .01 mph loss you won't notice. I prefer the extra protection. When I haul in the fall, top and bottom are half gone.
 
Never considered this before. I’ve always just used top and bottom zincs on my tabs.
I’d be interested to see what if any differences in the performance data is between just using a zinc on top of the tab or using them top and bottom.
 
JVM225 said:
Never considered this before. I’ve always just used top and bottom zincs on my tabs.
I’d be interested to see what if any differences in the performance data is between just using a zinc on top of the tab or using them top and bottom.
Click to expand...

Been documented several times on different forums that Bennett recommends zinc on top of tab only. Maybe Tabman will stop by to confirm.
 
We don't have performance details on having them on the top only vs top and bottom. However having them only on the top is what Searay and all other boat builders have specified for the 20 plus years I have been with Bennett.

In fact, one of my first jobs was swimming in at the local yacht club replacing zinc anodes on Trim Tabs. Had to be around 1970! And they were only on the top. Who knew then I would become "Tabman" years later!

Tom
Bennett Marine
 
Too late for this year since I splashed almost two weeks ago but I’m going to give it a try next year.
I currently use rudder zincs on the tabs. What zincs would I order for use only on top of the tabs?
 
Tabman said:
On a boat that size an R-4 rudder zinc would be what I would use.

Tom
Bennett Marine
Click to expand...
Crud, so my 400 Sedan Bridge should have one R4 on the top instead of the two R3 on top and bottom, which the diver always put on. I recently switched to just one on the top and put on the r3 size. So that's not enough zinc?
 
No, that will be OK and probably what we would install at the factory. Next time though you may want to go up to the R-4. I would not bother changing them now.

Tom
Bennett Marine
 
Thanks Tom. Do I need to sand away the extra diameter of tab paint for the r4? Or is an r4 on top of an r3 footprint good enough contact?
 
So it sounds like you just use one half (the one with the nut in it)of the rudder zinc on top. What kind of hardware would be used, or can I just use the Allen Screw that comes with the rubber zinc with a flat stainless washer in place of the other half of the zinc I won’t be using and insert it from the bottom?
 
Last edited:
You must log in or register to reply here.

Forum statistics

Threads
113,154
Messages
1,427,383
Members
61,060
Latest member
Danileo
Back
Top