engine mounts

chortle

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I would like to put some soft mounts under my existing engine to reduce vibration and noise. The front is hard mounted, the back has the original soft mounts so they need to be replaced. Really no room to move the engine up and down. If need be there is a fair amount of room to move her fore and aft. No easy way that I can see to reuse or remake the existing mounting bracket on the front of the engine. I suppose new brackets could be made to fasten through the sides of the existing fiberglass angles and set the new mounts there. Maybe need to be set upside down so they hang? Move the alternator and raw water pump? Any other ideas?

Cat 3160 after cleanup.jpg

tight overhead clearance.jpg

aft mounts.jpg

stbd engine mount looking aft 1.jpg

stbd engine mount fwd.jpg

port fwd mount looking aft.jpg

port fwd mount.jpg

port aft enigne mount.jpg

oil pan clearance.jpg
 

Toolate

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Is that a down angle trans? Could change to a straight gear and that would lift the front mounts up off the fiberglass angles plenty.
 

Ol Gilnetter

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petrel

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Is that a down angle trans? Could change to a straight gear and that would lift the front mounts up off the fiberglass angles plenty.

He might have to get some welding done, but I expect it can be done w/o having to buy a new clutch.
 

chortle

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Thanks to all for the comments and thoughts.

KEELBOATER: The soft mounts on the tranny are the type I would expect to use but do not have a specific brand/model selected. They look to be plenty big and I would expect that whatever new ones I put in there would fit without modifications.

TOOLATE: I only have one inch of clearance between the coolant tank filler cap and the deck support beam so I don't want to raise the front of the engine buy changing the tranny angle. I could move the engine forward two or three inches and gain two or three inches of headroom but the driveshaft would have to be extended or maybe a soft coupling added? That could be a benefit.

OL GILNETTER: Nice sketch, it shows the scenario pretty well. I will go down to the boat today and make some measurements around the mounting feet. I am hoping to keep the existing glass angles and add a metal bracket as you have drawn. I suppose I could make a new bracket that would raise the alternator and water pump. I don't see a problem with that other than some extra cost. I will add the dimensions that I collect, put them on your sketch and re-post.

I have seen some support for Barry Mounts and Soundown mounts, any other candidates out there that folks have had experience with? Anyone mount them upside down?
 

Ol Gilnetter

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harris 28

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Chortle....I am no marine engineer but it seems to me if you are soft mounted in the back and hard mounted in the front,the back can move and the front can't where as that could give you unessessary vibration.Kinda like the same theory of putting on four radial tires on a car. Not supposed to put just two on. Maybe you are better off in this case to go hard mounted all the way.It would be a lot easier to do so. I've had three hard mounted engines in three different boats and have had no problem if it is done correctly. Other than checking alignment ever so often I didnt have any unessasary vibration and if I did the boat will let you know. Hell,I still check the alignment with soft mounts with witch I have had problems. Maybe you can talk to Travis or SW or somebody who knows more than I do about this idea.Think it's worth a shot!
.
 

petrel

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That probably makes the most sense. Hard mount the clutch.
 

Brooksie

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Hard to get the whole picture from the photos but if the heavy fiberglass angles could be cut down and angle iron bolted to the remainder, then soft mounts could be squeezed in. Engine stays where it is.
A second option might be to make up new steelwork for the front with the feet higher so the mounts will fit between them and the existing FG angles. Again the engine stays where it is but the alternator may need to be moved, or swung up and the adjuster relocated to the top.
A third option is also new steelwork for the front with a single mount in the center down low. Perkins did this on their horizontal engines and never had a problem using just 3 mounts.
Some good mounts for the Cat are from PYI they are shear type but they are not exactly low profile. If you can allow for shear type mounts, they do work much better than the compression type you have now.
 

mudhake

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that's a no no, hard in the front and isolators in the back, that's strange, both working against each other.
 

Toolate

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Looks like the front mounts are part of a single bracket that spans the whole front of the engine (looks like its bolted to the block on either side of the dampener?)- is that the case? Find some low profile mounts and have that remade with the front portion raised up by whatever the added thickness of the mounts is. Move accessories as needed- probably the hardest part.

Is this worth it? Has anyone changed to soft mounts and really noticed a huge difference?

No way to use a more standard gas engine style mount? Any holes on the block sides to work with?

image.jpg
 

chortle

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Some more good thoughts from several folks, thanks. Interestingly, the engine was supplied by Cat with soft mounts on the tranny and a big steel yoke up front for mounting but they did not supply soft mounts for the front. The boat was built this way as a pleasure boat in 1972 and I have seen other old lobster boats (working and pleasure) built like this too but most all boats in the recent past have soft mounts on each corner to minimize the vibration from the engine to the boat.

My current thinking is to put a temporary tripod support over the motor so that I can lift it up and inch and hold it there while I pull the yoke off the front of the engine and remake it with some raised support wings on each end or a modified hot rolled tee section as shown in the sketch below to accommodate a pretty standard type of isolator that can sit on a bracket bolted inboard of the fiberglass angles that currently support the front engine mounts. I may be able to do this without moving the alternator on the starboard side, the water pump on the port side may need to be rotated up and inch or two. The FRP angle is 3/4" thick and 3"x3" legs. The top of the engine mount bracket that came with the engine is 3" below the top of the FRP angles and there is 3" between the FRP angle and the engine.

More thoughts?

See sketch and pictures below.

link to some more photos of the engine mounts
https://plus.google.com/photos/100807000759304457569/albums/5959146713989594993?banner=pwa

NEW ENGINE MOUNT BRACKET 001.jpg

stbd engine mount looking aft 1.jpg

stbd engine mount fwd.jpg
 

chortle

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Here is a sketch with dimensions. Thanks to OlGilnetter for the CAD work and ideas. I think that am going to try and fit an isolator in between the engine and the FRP angle so that I can keep the angle and not have to remove the engine. I still need to get a selection for the isolator from a couple of suppliers to see if it will fit and I am still interested in more ideas and comments from the forum.

sketch with dimensions 001.jpg
 

Brooksie

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Idea: Don't use compression mounts, use shear mounts. This will make your work worthwhile.
 

chortle

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Brooksie, you have recommended shear mounts, I'm interested, what else can you tell me about them? Have you changed out compression mounts or added shear mounts with good results?
 

Toolate

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Will you be able to turn the lower set of adjustment nuts?

Looks tight as hell but good solution if it can be done.
 

chortle

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Yes, that lower nut and the bolts that attach the isolator to the angle bracket may be a total bitch. I need to make a final selection for the isolator and do a couple more scaled sketches to confirm the plan. Still looking for better options or ideas. Won't pull the trigger until after the holidays. Will post photos when they happen and results this spring when she launches. Keep them cards and letters coming.
 

petrel

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If you get some hard mounts welded up to replace the isolators at the clutch and shim it up right, you won't need to be adjusting stuff later. But maybe it will be too much noise? I don't know. It would be way easier to hard mount the clutch. I don't know what to tell you. I've got hard mounted 671's that are quieter than a Cummins 6BTA on isolators, but it's different boats w/ different decks, so apples and oranges.
 
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