FL120 Motor Mounts

Hey!

We've got paint in the ER of this Chris Craft Roamer we're putting back together, which means engines can go in soon.* I've got Lehman 120s w/TD502 gears and I'm inclined to use engine mounts.* Do you guys have any particular makes/models that have worked out well for you?* I'm a Detroit kinda guy and don't have a clue what you use for little engines like the Lehmans.

Cheers

Q

RE: FL120 motor mounts

You can obtain engine mounts for the FL120 from American Diesel.

RE: FL120 motor mounts

Thermo Boat Ltd. offers engine mounts that I think are superior as they arent made with rubber. They can be had through www.thermoboat.com. They seem to act like a shock absorber actually absorbing vibration rather than just allowing for movement. The brand name is Poly Flex and they are made in Australia but there is a distributor in Surry British Columbia Canada.

Eric Henning
Willard 30
Thorne Bay AK

RE: FL120 motor mounts

I'm curious--Are the ones available from American Diesel particularly good or is AD just the first stop for all Lehman owners?

RE: FL120 motor mounts

Probably both. AD has a great reputation, and they will only sell you high quality stuff.

RE: FL120 motor mounts

So, the Lehman mechanic who said the OE mounts were a shade on the small size was just making things up? It wouldn't be the first time with this fella...

The price from AD is certainly better than anything else I've found online.

-- Edited by Libertarian at 08:34, 2008-10-09

RE: FL120 motor mounts

Go with AD. The owner designed the Ford Lehman. And they are super nice folks.

RE: FL120 motor mounts

The OE mounts some if not all boat manufacturers used with the FL120 ARE on the small side. They are not rated for the actual weight of the engine.

There are mounts available that are rated for the weight of the FL120. BUT..... on some boats like the earlier GB36s with two engines.... the right size mounts move the engine too high to clear the underside of the cabin sole floor beams above the engine. So either the engine stringers have to be modified (expensive), the mount brackets on the side of the engine need to be replaced with custom brackets (even more expensiv) or you simply go with the original, slightly too-small mounts. Since the original mounts on our boat lasted about twenty-five years before they compressed down enough to make metal-to-metal contact, we went with the original size mounts when we had them replaced a couple of years ago.

On a boat with more clearance above the engine's coolant header tank, mounts rated for the engine's weight can be used as long as they engine can still be brought into alignment with the prop shaft.

At the time we put new mounts on our engines American Diesel did not stock the original size "small" mounts.* Our diesel shop got our new mounts from Bushings, Inc.* The model number of our*mounts is*DF-100.

-- Edited by Marin at 13:44, 2008-10-09

RE: FL120 motor mounts

I saw the DF-100s on go2marine for $36/ea. But the engine weight supported was only 850#. The fellow at go2 said that was for a set of 4 per engine. http://www.go2marine.com/product.do?no=75045F

The DF 216 is rated up to 1200#, or 300# per mount for a 4-mount system. I figured I could just run six of them (4 on engine, 2 on gear).

But then I went to the Bushings Inc website, where they have a cross reference guide. I was surprised to see the weight of Lehman diesels listed at 2800#. I'm a Detroit Diesel guy, so I'm accustomed to seeing 2800# sixes. I'm thinking there's no way the little Lehman tops out over a ton.

So, I went to boatdiesel and looked at the Lehman 135 spec sheet, which says these things tip the scales at 1374# minus gear.

Sooooo, it looks like even the 216 would be slightly undersized even if I ran six of them. I've written back to AD and asked if the ones they sell are properly sized for the engines. I'll report back what they say.

RE: FL120 motor mounts

According to the Lehman 120 operators manual, the weight of the 6-cylinder FL120 is 1,092 pounds without the transmission. Since these are the Ford specs for the engine, I suspect this weight does not inlcude the Lehman water-jacket exhaust manifold, the raw water pump, the three heat exchangers, and whatever else Lehman put on the engine to marinize it.

RE: FL120 motor mounts

It sounds like the 1374 number from the boatdiesel spec sheet might be the one.

This just in from AD:

What the heck does*your mechanic mean by marginal? We put them on about 15,000 engines.

The better mounts we offered were less ridgid so the engine could move around a lot more to eliminate so of the low speed vibration. These other mounts have different bolt down dimensions fo the beds need re working. What are you trying to accomplish? Also, the other mounts are more expensive.

We can supply whatever you would like, but caution that more movement of the engine could cause other problems. Again, what are you looking for with the mount change.


-- Edited by Libertarian at 15:36, 2008-10-09

RE: FL120 motor mounts

I can assure you that Bob and Brian are the most knowledgeable people you can get for the FordLehman. I purchased an FL135 to put in a baybuilt boat and have got nothing but good advice from them.

RE: FL120 motor mounts

I've always wondered about the 25 year old mounts on my FL120, how do you know when they are worn out?

RE: FL120 motor mounts

The rubber bushing in the mount compresses to the point where there is metal-to-metal contact inside the mount. So what you see is the upper disk of metal "collapsed" down inside the "cup" of the lower mount. The rubber inside the mount just looks "flat." Not much of a description, I guess, but that's the best I can do based on what our mounts looked like before we replaced them.