Engine Mounts

Del

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I'll soon be pulling my HT6.354 Perkins (150 HP) from my 1970 34' Webbers Cove to fix a rear oil seal. The motor front mounts are fixed while the rears are isolated. I imagine less vibration, quieter operation if all four mounts were isolated, so have been considering mount replacement to accomplish this.

What thoughts are out there regarding the functional value of this change? Could it be that solid mounts are used to optimize engine thrust transfer to the hull and changing that characteristic would shorten the life of other components or introduce other issues?
 

captainlarry84

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Your hard front mounts are fine. You will pick up little by changing them. The big key in engine mounts is that two should be on the gear and two one the motor. Four on the motor which I have seen on may N/E boats is not the way to go.

Picture 4902s.jpg
 

Del

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Your hard front mounts are fine. You will pick up little by changing them. The big key in engine mounts is that two should be on the gear and two one the motor. Four on the motor which I have seen on may N/E boats is not the way to go.

I believe I have 3 on the engine and 1 on the trans., but need to verify that.
 

Del

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Your hard front mounts are fine. You will pick up little by changing them. The big key in engine mounts is that two should be on the gear and two one the motor. Four on the motor which I have seen on may N/E boats is not the way to go.

Glad to hear hard front mounts are OK. I wonder though whether alignment isn't more difficult with hard mounts. I have no experience with the process of aligning an engine (yet), so with hard front mounts I assume alignment adjustability at that end must be handled with shims. Are there double-wedge shims to permit accurate adjustability or must shim thickness first be measured then fabricated? I have a feeling this is a rudimentary question that everyone knows but me.

I've noticed threads talking about tweaking their alignment to within 6 thousandths and the like. I can't see how a 1200 pound engine can be moved precisely into alignment with the shaft unless every mount has height adjustability while supporting the engine. I know there are guys on this forum who have done it, I'd just like to learn how.
 

Del

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With the engine out, I now know how my 150 HP Perkins is mounted. At the front there is a yoke solidly mounted to both stringers, using spacers for adjustment. The engine then has a single vibration-isolated mount fastened near the center of the yoke. At the rear, one mount fastened to the engine and another off the gear. So, three rubber isolation mounts total.
I intend to replace the 3 mounts. Any recommendations on mount manufacturers?
 

captainlarry84

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Aliment with solid mounts and shims is not easy and it is an art. If it was my vessel I would go with four Barry Isolated Motor mounts. Two on the gear and two on the front of the motor. Aliment will be pretty easy and basic with four of the same mounts. The problem with changing your front mounts is will the new mounts be two high as currently your motor sits hard on the stringers. You may have to do a little glass work on the stringers to except the four isolated mounts. There is no doubt that the boat will be smoother and hold an aliment better.
 

BillD

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Hard mounts or soft mounts

In my travels looking @ DE keel boats I never really "looked closely" @ engine mounts.


I've spoken with a few builders and never really asked the questions about engines until today.

One builder stated that "hard mounts" are highly recommended in lobster boats.

Something about soft mounts allowing the engine to move back and forth and changing the angle to the shaft coupler screwing up alignment and causing even more vibration.

Mike's 33 Flowers QSC 500 has Barry mounts (see pic)
Here's a pic of a nice DE that has a hard mounted QSC (see pic)


Who runs hard mounted engines on this forum and who runs soft mounts.

Larry, from your picture it looks like you Yanmar has Barry Mounts.

Travis, I "think I recall" you favor "hard mounts" in your boats. If I misquoted you I apologize.

Cummins engines come with Marrys as do I "think" the FPT Ivecos. mounts.

Are Barry mounts considered "hard or soft" ?

What's the scoop on mounting these engines in keel boats?

Seems like a hard mount engine would transmit vibrations/buzzin or something more annoying than a soft mounted engine would ?

Isn't boating suppose to be fun ? :D

QSC 500 Barry Mounts.jpg

IMG_0779.jpg
 

plowin

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"Soft" mounts are typically called vibration isolators, no explanation neccesary. Lobstermen and typically anyone who is running a shaft driven PTO for there hydraulics will ideally have an engine that is hard mounted or bolted directly to the angle iron or engine bed. This is because with the amount of torque generated by most engines the engine will move from both side to side and front to back, soft mounts allow this and hard do not. You do not want your engine moving and stressing your PTO,which is also typically fixed or hard mounted, thats where the hard engine mount comes in to play.
 

F/V First Team

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Hard mounts come in to play anytime the engine is running. Not just for things that are jackshaft driven off the front. Anything belt driven would be subject to the misalignment "allowed" (created really) by those damned soft mounts.

If there is a wiggle when the boat is idling, there's something wrong with your engine, it is out of balance. If there is a wiggling when the boat is in gear there is misalignment somewhere along the way. Coupling, shaft, stuffing boxes, stringers not being stiff enough, etc etc.

Any movement of the engine that isn't rotational at the flywheel is wasted horsepower. You're loosing efficiency, speed and you're wasting fuel.

"Well my car is soft mounted with its engine" - isn't that just dandy. It also has springs and shocks as well as universal joints to take up the slop as you hurl yourself down the highway. There are no shock absorbers out there on the high seas, but plenty of holes to find yourself in. I don't want any undue stress put upon my drive train and I expect my engine to be exactly where I put it, pounding as much power as I can into the water so I can get home.

If I had a customer who absolutely DEMANDED that the engine be put in with soft mounts, well, it would have a price tag associated with it. And not a small one either.

Just my opinion, I know it doesn't mean a whole lot, but it's mine and I hold it dear.
 

Blitzen

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I find it interesting that the rest of the boating industry uses soft mounts. Are they doing it wrong?
I have been on boats with 2000HP engines mounted on soft mounts with out issues, non commercial that is.
I see it as big benifit in commercial applications where the engine is hard mounted, that the constant forward/reverse thrust works direct to the hull/mounts, but for a non commercial applications soft mounting an engine is fine if you know how to do it right. As CaptainLarry stated two mounts on the front of the engine and two on the gear is the industry standard.
It makes for a smoother quieter boat. IMO
 

El Mar

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BillD

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"Soft" mounts are typically called vibration isolators, no explanation neccesary. Lobstermen and typically anyone who is running a shaft driven PTO for there hydraulics will ideally have an engine that is hard mounted or bolted directly to the angle iron or engine bed. This is because with the amount of torque generated by most engines the engine will move from both side to side and front to back, soft mounts allow this and hard do not. You do not want your engine moving and stressing your PTO,which is also typically fixed or hard mounted, thats where the hard engine mount comes in to play.

I find it interesting that the rest of the boating industry uses soft mounts. Are they doing it wrong?
I have been on boats with 2000HP engines mounted on soft mounts with out issues, non commercial that is.
I see it as big benifit in commercial applications where the engine is hard mounted, that the constant forward/reverse thrust works direct to the hull/mounts, but for a non commercial applications soft mounting an engine is fine if you know how to do it right. As CaptainLarry stated two mounts on the front of the engine and two on the gear is the industry standard.
It makes for a smoother quieter boat. IMO

There are two DE boats in our area where the owners have complained of a "frequency" or "annoying" noise in the pilot house when the engine is running, to the point where it is uncomfortable to be in there. Not necessarily loud, just bothering.

One is commercial, one is recreation both keel boats and both mounted with hard mounts. Coincidence?

I have never been on either boats, just hearsay around the waterfront so take it with a grain of salt.

Interesting discussion.

Mike? Good explanation, you are running your hydraulics off the back of the transmission and NO hauler on the boat.

John? Is you CAT soft mounted in the 36 Flowers?
How is the boat setup for hydraulics?

El, I'm still sorting out the mechanicals of my "virtual DE build". !:D
 

Blitzen

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Bill,
My engine is mounted on Barry Control mounts and is smooth as silk. I have no vibrations or dancing water over the wheel at any RPM.
I have a gear mounted hydraulic pump with a 6 or 7 gallon tank.
 

plowin

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Yes Bill my hydraulics are "live" PTO driven off of my transmission and have been sized for a hauler, although not installed yet, but hardcore lobstermen and users of the hydraulic system almost always utilize an external pump and PTO. I think that the engine mount issue, just like anything else, is really dependent upon what you are trying to accomplish. Additionally lobstermen are using there boat solely as a tool and if your using vibration isolators you have just added several hundred more dollars, unecessarily to the cost of that tool In my case when using the harpoon I am trying to send as little noise and vibration through the hull as possible. If I were Travis or any other lobsterman I would probably hard mount, so I guess that in my opinion there is no "right" way, just "right" for your application.
 
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