So my Thomson trim unit on my Mudbuddy HD Sport has finally died for good, the screw drive and bearings have rusted out and fallen apart, motor still works, but screw drive portion is shot so after 7 years its time for a change.
Not paying $1100-1200 for the Mercury trim retrofit.
After researching prior post and help from Denny on this forum I have decided to buy one of the Concentric linear actuators to replace the Thomson with, it looks very similar.

A couple of questions for anyone that has done this.
1. Did you buy the 500lb Acme drive or the 1,000lb screw drive unit?
2. Did you buy the 4" unit or 6"?
3. Did you add a zerk for greasing it and did you drill a release valve similar to what the Thomsons have?

Mudbuddy wants $400 for basically the same thing I can purchase for about half that. Also does anyone know the actual pounds of lift on the original Thomsons?

Thanks for the help.

Nobody?

TTT. I would find this info useful as well


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I will let you now how it goes in a week or so, I ordered it yesterday and will install it as soon as it arrives.

Concentric Acme Drive linear actuator 4" model, the measurements of the unit match up almost identical to the Thompson, only difference is that it travels and additional inch higher but will go just as low. 500lb lift and 1,000 lb static load should be good enough.
Cost is $180 from Surpluscenter.

Update
I got the trim unit and added a release valve and installed it. Same exact size as the Thomson, installed the same way with the same mounts and works great.
It actually raises the motor higher than the Thomson, it stops about a 1/4 inch from the travel lock position. Time will tell if it will last.

Good job. Post up the Item # case any one else wants to save some money. We're looking into fabing up a bracket to use a mercury trim unit to replace the Thompson unit. It will be mounted to side of motor instead of under it. Something like the older add on trim units offered by OMC years ago for their 40-50 hp OBs. Complete Mercury trim pumps are offered on Amazon also. Also have a Merc. trim pump from a Bravo 1 OD which could be mounted inside boat on transom and piped to trim cylinder on motor. If we can find the right length of cylinder. Our dual exhaust keeping us busy right now.

Concentric Linear Actuator
Model LACT4-500A

Good deal that you got it replaced, that's a decent price for replacement.

Well it has turned out not to be such a great deal afterall.
After a few hunts and some long runs from the ramp this week it appears this trim is not going to work out. IF it was not for wacking the ducks really hard this week I would really be disappointed more than I am.
It will trim up and down but under a load or pressure on the motor it goes down, started out working fine but now it just goes down once on pad. When I got home today I just applied pressure to the motor and it would just go down. Not sure why since it is a Acme screw drive but it is supposed to hold 1,000lbs.

What ever happened with the new unit? I'm going to try the same route, but not sure how to tap and insert breather tube / zerk fitting.

Anyone else fine a good replacement for the Thompson Trim??