Marlin 300 - Trim Tab/Plane Replacement

[Fido]

Hi All,

Would love some advice.
Have today noticed I have lost a second trim tab in just 12 months. Previously the entire tab was ripped off this time just the rear section only. It looks as if the bolts have somehow come undone. I am hoping they were installed correctly as under pressure I was under the assumption the pin should let go first.

Seriously considering changing to Zip Wakes.

This is our third Grady and first this has happened to - getting a little tired of it!!!

 

[Halfhitch]

If the motor is trimmed down and heavy throttle is applied in reverse with the motor turned "hard over" while maneuvering then the thrust column of water can damage trim tabs. Recessed tabs are not so likely to be harmed. If the motor is trimmed up a bit so the reverse thrust water mostly travels under the hull instead of slamming into the transom it helps alleviate damage to things extending from the transom. Try using discretion when maneuvering and use minimal throttle in reverse and see if your tabs stay on.

I don't know your style of operation. Just offering one possibility. Another might be sea lions trying to climb on your boat. Where do you live, where is your boat stored? In the water? On a lift?

 

[DennisG01]

Generally speaking, Bennett tabs are one of the most reliable things on a boat. The "problem" with that, is that most people don't give them a second thought till there's a problem - and it's reasonable to expect the screws to be checked/tightened/re-sealed every so often as preventative maintenance.

What year is the boat?

Stuff floating in the water can cause damge.

EDIT: Added more info for clarity.

 

[Fishtales]

Never a problem. I'm guessing you have an issue with the mounting of them?

 

[glacierbaze]

What 'pin' are you referring to? It's odd that everything would go at once. Unless the design has changed, the mounting plate traps the trim plane against the hull, but they are not locked together. I would expect the plate to be loose, but not gone.
I would suspect some wet or soft wood, or outright voids in the transom.

 

[Fido]

This is a 2007 Marlin 300, we are based in Brisbane, Australia.
When we lost one plane 12 months ago I replaced both.
We predominantly gamefish for Marlin and therefore reversed is utilised while fighting fish. I am aware of trimming motor up etc. there are boats with them mounted completely proud of the transom - perhaps I am just having a run of bad luck.
The pin I am referring to sits between the ram and the connection to the plane. My understanding is that this is meant to ‘let go’ under excessive force before the bolts let go or something breaks.
I have noted the Canyon 456 utilises Zip Wakes.

 

[Meanwhile]

Is corrosion an issue? I now use zinc on my trim tabs as I found a couple screws had degraded and popped the heads off. I have the same year Marlin.

 

[Fido]

Is corrosion an issue? I now use zinc on my trim tabs as I found a couple screws had degraded and popped the heads off. I have the same year Marlin.

Yeah big anode on both tabs!!!

 

[DennisG01]

Not that it isn't true, but I have personally never heard of that pin being the purposefully designed "weak link" so I can't comment on that.

Chances are it's just a fluke thing. It could be a soft transom, but hopefully not. Could also be that if you reused the same holes (which is fine), they weren't gripping the screws well enough. Some adhesive caulk helps here. Most likely you just snagged something again - or lot's of reversing with them still fully deployed just took it's toll on them.

They're excellent tabs - used around the world by tens upon tens of thousands of boats very successfully. I wouldn't let a relatively isolated incident lead you to the conclusion that just because you had these issues that it's time to jump ship and switch to the other style.

Edit: Grammar. First word should be "not", not "no"

 

[Fido]

No that it isn't true, but I have personally never heard of that pin being the purposefully designed "weak link" so I can't comment on that.

Chances are it's just a fluke thing. It could be a soft transom, but hopefully not. Could also be that if you reused the same holes (which is fine), they weren't gripping the screws well enough. Some adhesive caulk helps here. Most likely you just snagged something again - or lot's of reversing with them still fully deployed just took it's toll on them.

They're excellent tabs - used around the world by tens upon tens of thousands of boats very successfully. I wouldn't let a relatively isolated incident lead you to the conclusion that just because you had these issues that it's time to jump ship and switch to the other style.

Just to clarify. The front section is still attached to the underside of the hull. It is the rear section from the hinge point back which has been lost. It has detached and the ram still in tact. 2 x tabs in 12 months isn’t isolated and I don’t read of inherent problems. As mentioned we have had previous Marlin 300 and Sailfish 282 which never experienced a problem.
Unfortunately this trim plans isn’t available in Australia. So the tab and freight alone will be circa $1500 before lift out and fitting.....

 

[DennisG01]

I said "relatively" isolated. What I meant was that, although you had it happen twice in a year... and granted that is strange... it's by far the "rarity", not the norm. Logically, there's a better explanation for this than a defect/break.

Are you sure the ram mount is intact? I would expect to at least see the two mounting holes in the lower mount stripped out. After the tab broke free from the lower mount, it eventually worked it's way out from the hinge. You should at least check to see if the transom mounting screws are still tight. If they were tweaked as the plane came loose, they could be letting water seep into the transom.

If I remember correctly, there is a small, crimped section of the hinge that helps to keep the plane inside the hinge. When you installed new planes, did you verify that and/or re-crimp it?

 

[glacierbaze]

Not that we can solve your problem, but from a detective standpoint, it would be nice to know which end of the connection let go, if you can tell. I am guessing the hinge, which would leave a flapping plane attached to the actuator, for a while. If the ram let go of the plane first, it should just flop up and down in the hinge long enough for you to realize that your trim wasn't working correctly. Or, if the bolts came out of the actuator, and the tab was hanging down at low speed, and you backed hard against it, forcing it into an angle that it was never designed for, it might pop out of the hinge. I find it hard to believe that reverse prop thrust would damage a Bennett tab.
All of my trim tab experience has been with transom mounted tabs. If yours are in a pocket, the hinge mechanism may be different.