Ford Lehman Damper Plate Replacement

Hello All,

First post by a first time Trawler owner. Love the forum and have been reading it for months now.

Just purchased a 1983 Universal Tri-Cabin with twin FL120s. The engines have 4300 hrs on them. The DPs are supposed to be replaced after 2500hrs so either that has happened or needs to happen soon. The rear engine mounts are actually on the transmission.

I have approached the previous owner about any service done on the boat to see if the damper plates have ever been replaced and am waiting for his reply.

In the meantime, I am wondering if anyone is aware of a shop manual or instructions on how to do this. I was thinking of buying two mounts for the engine to temporarily support it while working on the DP.

I have watched Winty work extensively on his FL 120 and there is one video where he starts to discuss this (his rear mounts are on the transmision as well) but then he moves on and never comes back to it.

Any info would be appreciated. Thank you in advance.

I was thinking of this just the other day my 135 has a spot to mount 2 home made brackets and they could have jack bolts to lift with . I am going to go ahead and have some brackets made. you will probably have to loosen something on the front mounts so they can pivot.

There is a thread on this on forum. Others have added rear mounts or just block support engine.

I was thinking about making something like that as well although it would be nice to be able to buy the FL mounts that are designed for the rear of the engine. They may not be available though.

Thanks Steve, I will have a look for that thread.

You can easily go 5000 hours so don't lie awake worrying about it.
While you have the transmission out replace the front seal.

I changed my port damper plate last winter when I had the engine out. Since my engine was out it was really simple. Yours will be a bit more difficult but doable. I would just block the engine up. You don’t want to leave an extra set of mounts on full time IMO. Once you get the engine blocked up you can replce a couple of the bolts holding the transmission on with some longer bolts or all thread so you can just slide the transmission back, replace the damper and slide it forward and bolt it back on. You will have to be able to slide the prop shaft back so the transmission will slide back.

Another note, do you know about changing the oil in the fuel injection pump? On the 120s they have a baseline of 50 hours to start. Can lengthen the interval if the oil is still good at 50 hours and gradually move up as you check the oil. But probably not over 100 hours, per Bob Smith before he passed.

Thank you, that is great information.

I have ordered the two manuals offered by AD and see what instructions they have on this.

Blocking the engine aside, is it simply a matter of taking out the bolts holding the Bell house to the back of the engine and then the whole thing just slides back on the drive shaft? Seems too easy.

Kevin.Bridgen said:

Thank you, that is great information.

I have ordered the two manuals offered by AD and see what instructions they have on this.

Blocking the engine aside, is it simply a matter of taking out the bolts holding the Bell house to the back of the engine and then the whole thing just slides back on the drive shaft? Seems too easy.

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It is that easy. The only hard part is getting the transmission slid back. We used some locktight on the damper bolts, not the really hard stuff though. I used a floor jack to support my transmission since they were out of the engine room. Just put a small piece of plywood on it to spread out the weight on the oil pan. Then rolled in back a few inches, maybe 5 or 6” and unbolted the old damper and bolted on the new one and then rolled the transmission back up and bolted it on. If you get some all thread the right size and cut it long enough to slide the transmission back it will make it easy since you won’t have to hold the weight of the transmission. I am not sure if you will need just 2 all thread or maybe 4 depending on transmission weight.

It is simple but...
2 4" setup studs in the lower middle threads will make removal/reinstallation a lot easier. I disconnected the prop shaft to make it easier to move and I did not want 275 lbs hanging off the end of the shaft.
I made a frame and used a chain hoist to hold weight of transmission. Lifting it and aligning it is a bit of an effort.

All manuals are available online at no cost.

I used anti-seize on bell housing bolts to make future removal easier.

Thanks SoWhat,

The chain hoist is a great idea to support the transmission. Next time I am at the boat I will see what my options are for spreading out the weight on either side of the engine hatch.

You won’t need something this substantial but this is what I made to lift the engine and transmission out together. My engine and transmission weigh 1350 pounds approximately. Note the caution tape and white towel hanging from the I beam, put them up after I had whacked my head a couple of times...

Damper plates

Hi Kevin,
The job is not a difficult one. If you search the forum I’ve posted pictures when I did mine. I used a 4x4 with a come along to slightly raise the engine. It helps to have two people when removing the transmission.

The pictures are under the subject of “oil leak”
Good luck

Perfect, Thank you!

Thank you GBInterim, Love the pics. Will post how it goes. (Unless the PO gets back to me and tells me they have been done.)

I am not looking for extra work but would prefer to limit the number of issues while out. Have already had to put on a mask and snorkel in the middle of the Georgia Strait with our last boat and would rather avoid anything going wrong with this one if possible.

Mine cost $250 each but I would rather do it on a preventative basis that at a time that we are out in the boonies and have one go out. I had no idea how old mine were so now I have a baseline to start with.

Thank you Comodave, Everyone on here has been really helpful

We did ours in about 2.5 hours.

Go to grandbankschoices and find the thread.

A simple process that I can not believe people don't do for $150.00. If the dampner fails it usually locks up the engine mechanically by jamming parts between the flywheel and block or bellhousing. Now you have to pull the flywheel.

As it fails it allows vibration on to the trans input shaft, destroying seals, bearings, and gears.


Ours had one spring left, and we were preparing to cross the Mississippi in New Orleans. A failure would have probably resulted in a loss of the boat and all hands.

Kevin, once you get the engine supported and are ready to unbolt the tranny, take the time to pull one of the upper two bolts and then go and get two of the same thread about a foot or so long. Cut off the hex heads and cut a screwdriver slot across the end of them. Now replace the top two bolts with these special tools you have made, and with all the other bolts removed, you now have a pair of rails to slide the tranny out of and back into position. I watched a very talented mechanic change my stbd Velvet Drive plate out at around 5000 hours. I understand the other is still doing well.

Wow! that is a great idea! Thank you!

Photos, 1 with chain hoist, one with rachet. Rachet was preferable. Note frame with 2X6's. 2X4 on top with a trolley attached so I could move transmission to center. Made it easier to change front seal and install new dampers. Total time - about an hour each side.
Support the weight of the transmission so the shaft will slide out of the spline. It must be straight. Turn the rear coupling to align splines when reinstalling.

(Yellow arrow points to setup stud permanently installed with a nut rather than the original bolt. Exhaust hose is removed. I placed scrap wood under transmission for safety.)

Guess I am lucky. My Lehmans are supported by four motor mounts. The transmissions are simply bolted to the engines.

catalinajack said:

Guess I am lucky. My Lehmans are supported by four motor mounts. The transmissions are simply bolted to the engines.

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Ditto.
Conversion mounts are available to eliminate trans mount, but I think 3 mounts may cause stress at the center.

I did my DP, motor mounts, tranny service, new shaft, new cutlass bearing, new rudder table, packing all around, and reconditioned prop about a month ago.

My damper plate was stuck on tranny shaft, so i did not have the most pleasant experience. But i think mine is a “one off situation and not common.

Lift up the ass of the engine by any means possible and follow the other folks instruction. See pics.

You certainly have easy, good access to the engine. I am jealous.

Comodave said:

You certainly have easy, good access to the engine. I am jealous.

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Lmao. You correct. (Now I dont have a nice big salon etc...., but groverbuilt’s have their bright spots, lol.)

Well there is something to be said for having a salon with recliners in it... Although right now my salon has a crane in it instead of recliners.

Damper Plates

First & foremost, ANY FL questions should be directed to Brian at American Diesel. They are the premiere FL source, since Brian's dad was involved in the marinaziation of the Ford engine.

They have what ever it is FL that you will need.

Here (https://americandieselcorp.com/) you'll find the phone number and any other info you need.

Second, are you referring to engine mounts as damper plates?

IF so, they have them. We did our 2 135's in '16. Don't think that engine mounts go to the trans, at least not on our 135's.

You'll hear a lot of comments on most forums, call Brian, that's the best choice.

There is also BOMAC Marine who rebuilds and a place near Seattle that does too.

Both had tech info on valve clearance to piston head after a head rebuild that I wasn't able to get from American Diesel.

So while American Diesel is great for a lot of things, there are more pages in the Lehman book.

Some Lehman installs do put mounts on the tranny, see post #25.