Flat Wood Bunks Ok for 2023 Tritoon?

dijman

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I have just bought a boat lift from a neighbor (picture attached). He had a V hull boat and I need to modify it for a 2023 Bennington 21’ SX Swingback with a 150 Yamaha engine.
My question, is it ok to use 3 flat 12’ 2x8 pressure treated flat bunks?
(Note, a dock installer near me is saying that Bennington says that the 3 toons need to be supported by a ‘V’ bracket, not flat bunks. Across from me in my marina are 3 21’ Bennington tritoon supported by flat bunks.) Thanks!
 

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My 24’ is on flat boards. Don’t use pressure treated though as it could react with the toons. I just replaced my regular pine ones after 5 years to be safe but they still had life in them.
 
Thanks. I’ll use non-pressure treated lumber. Should 12’ boards be long enough for my 21’ Bennington?
 
When they are flat there isn’t any load bearing capability aside from on top of the cross beams so extra length won’t matter. Mine are 12’
 
The boats sit flat on the ground or blocks at weld points at every dealer I’ve been to. I’d think you’d be fine if weights centered but me personally I’d try to go longer boards. That’s my personal opinion only as I always err on the side of overkill.
 
Do a search (upper right hand corner box). This topic has been hit on a number of times the past few years. V brackets are recommended, but plenty of people have flat bunks. I used to have v brackets on a lift before switching to Sea Legs. I am 99% certain a couple of members have reported reaching out to Bennington directly on this question and were told it was okay. Should turn up in a search of past posts on this topic.

My concern for you is I have read that pressure treated wood does not interact well with aluminum pontoons. I would look into that to see if that will be an issue.

My understanding is they should not come in direct contact with each other or it will lead to some sort of chemical reaction. I have heard you can “cover” the bunk to avoid the issue, but it’s all second hand info.

Since I was never going to use pressure treated bunks, I never looked into it further. Perhaps someone else that is knowledgeable on this particular aspect can comment below…
 
I have just bought a boat lift from a neighbor (picture attached). He had a V hull boat and I need to modify it for a 2023 Bennington 21’ SX Swingback with a 150 Yamaha engine.
My question, is it ok to use 3 flat 12’ 2x8 pressure treated flat bunks?
(Note, a dock installer near me is saying that Bennington says that the 3 toons need to be supported by a ‘V’ bracket, not flat bunks. Across from me in my marina are 3 21’ Bennington tritoon supported by flat bunks.) Thanks!
Same setup has worked for me the last 5 years.
I have just bought a boat lift from a neighbor (picture attached). He had a V hull boat and I need to modify it for a 2023 Bennington 21’ SX Swingback with a 150 Yamaha engine.
My question, is it ok to use 3 flat 12’ 2x8 pressure treated flat bunks?
(Note, a dock installer near me is saying that Bennington says that the 3 toons need to be supported by a ‘V’ bracket, not flat bunks. Across from me in my marina are 3 21’ Bennington tritoon supported by flat bunks.) Thanks!
Same setup has worked for me the last 5 years.
 
Obviously laying the boards flat on the lift crossmembers has worked because if not we probably would have heard about it. Now with that said I would think that the load concentration on the boat keel right above the lift crossmember is higher then one would think. A flexible board laying flat on the relatively thin crossmember does not distribute the load well. The good news is that the solid keel extrusion used by Bennington is very strong. In addition because it is not a sharp edge keel it is less likely to split the board.
 
We have flat boards as well (as do many of the lifts on the lake). Mine are 12 foot long.
 

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