Motor Mounts

[skipperdude]

Does anyone have this sort of set up as far as motor mounts go?

There doesn't seem to be any vibration damper. the mounts hang over the stringers and seem to be hard mounted with just bolts.

I was thinking of changing the mounts to provide for quiet and less vibration.

I'm thinking if I changed anything I would have to reconfigure the entire mounting system.

The 4 th pic shows the actual mount as far as where the bottom of the engine is mounted to the stringers.

SD



*


-- Edited by skipperdude on Monday 23rd of January 2012 11:35:06 AM

 

[Delfin]

I'm no expert, but that does not look like a system I would want to rely on.* It looks like the set bolts make contact with glassed over wood, and are chewing into it.* At a minimum, I would put steel pads on either side of the mount so the stringer is compressed by something other than the set bolt, but even then, relying on compression rather than a positive mechanical attachment seems sketchy.

 

[skipperdude]

Delfin wrote:
I'm no expert, but that does not look like a system I would want to rely on.* It looks like the set bolts make contact with glassed over wood, and are chewing into it.* At a minimum, I would put steel pads on either side of the mount so the stringer is compressed by something other than the set bolt, but even then, relying on compression rather than a positive mechanical attachment seems sketchy.

*Agreed. Bear in mind this system has been on the boat for 38 years.

It does seem an odd way to mount a motor.

*

 

[markpierce]

Not the best photo showing the Coot's motor mounts (picture taken to document small oil leak, since fixed), but it does show either half of the front and back starboard mounts.

*

 

[dwhatty]

The engines in most of the lobster boats around here are hard mounted to the stringers, although I can't recall if the setups resemble yours.

 

[markpierce]

Found this backside view.

 

[Marin]

While I have very limited experience and exposure to marine engine mounts, I agree with Carl. That does not look like a very good setup. The motor mounts on our boat and on the few other boats where I have paid attention to them, consist of a lower half that is mounted to the engine stringer and an upper half with a hard rubber doughnut, if you will, between them. The mounts on the engine block sit on adjustment nuts on a heavy, threaded rod in such a way that the weight sits on the upper half of the mount that's fastened to the stringer. These mounts are not soft because an engine mount that allows the engine to move around a bit--- like a car's engine mounts--- will not keep the engine in alignment with the propshaft. See photo.

The fiberglass engine stringers in our boat are capped with heavy aluminum extrusions that are solidly secured to the fiberglass stringers underneath and the mounts sit on the heavy extrusions, not the fiberglass itself. I have no idea if this is typical of other makes of boat as well.

An alternative if one want's to really reduce the vibration transmitted to the boat is to use--- like a car--- a flexible connection to the prop shaft, usually in the form of a U-joint and a sliding section of shaft. Now the engine can be mounted on much softer mounts because it no longer has to be held in rigid alignment with the shaft. The flexible system I am most familiar with by name is AquaDrive http://www.aquadrive.net/

 

[skipperdude]

The mounts that you folks are showing are the one's i was hoping to install but it really seems like a mojor refit to accomplish something like this.

After 38 years, I guess I will have to go with what I have.

I just found it strange to have the motor hard mounted and for what purpose?

SD

 

[Marin]

skipperdude wrote:

I just found it strange to have the motor hard mounted and for what purpose?

SD

*Well, if the hard mount is done right and the vibration is not detrimental to the boat, you never have to change the engine mounts.* Mounts like the ones in the photo I posted wear out over time.* The rubber doughnut gradually collapses and eventually it will collapse far enough to allow metal-to-metal contact beween the upper and lower halves.* At that point the mounts have to be changed.

While it's not rocket science to do this, you do have to disconnect the prop shaft(s), figure out how to jack up the engine(s), and then after the new mounts are installed you have to re-align the prop shaft(s).*

After 25 years the mounts in our boat were getting really tired in 1998.* We knew this when we decided to buy the boat, but they went another five or six years before a surveyor said, okay, that's it.

Like I said, the process to change them is not rocket science but I don't have the time, experience, or tools to do the job easily, particularly in the confines of an engine room.* So we hired the job out to our local diesel shop.* They said it would take two days of work for two people to do both our engines, and that's exactly what it took.* And they did it right the first time, so for us it was well worth the money.

Someone with more time, more experience, the right tools for lifting the engine(s), aligning the shaft(s) and so on, could easily do it themselves if they had a mind to.

But witha hard-mounted engine, which Dave says a lot of lobserboats use, it's not an expense or down-time that will ever be incurred.

 

[skipperdude]

Marin wrote:skipperdude wrote:

I just found it strange to have the motor hard mounted and for what purpose?

SD

*Well, if the hard mount is done right and the vibration is not detrimental to the boat, you never have to change the engine mounts.*

But witha hard-mounted engine, which Dave says a lot of lobserboats use, it's not an expense or down-time that will ever be incurred.

*I guess it is one of the lessons learned when refitting a commercial boat built for work and not pleasure.

It sounds like the boat is just set up that way I think I will just let it go.

*Great insight as to methods of mounting an engine.

"I did Not Know That."* Thanks

SD

 

[Marin]

In my previous post I worded it badly. After replacing worn engine mounts you don't "re-align the prop shaft(s)" you re-align the engine(s) with the propshaft(s).

 

[Bendit]

The engine in Pioneer is hard mounted with heavy fabricated steel plates sitting on top of, and through-bolted to the engine beds. I don't have a pic but they are a bit more substantial than what you have shown. Of course, the engine is 14.6 litres (Cat 3406) and* heavy so they need to be large.

The engine has been in the boat for 32 years and, apart from a bit of surface rust, they seem fine. If everything is fine after 38 years, I wouldn't want to change things too much. Shaft alignment, once correct, never needs to be adjusted.

 

[Badger]

My new to me aluminum boat has a hard mounted Perkins. Yes there is quite a bit of noise, no vibration. A noise reduction would be nice, but it is not as simple as swapping out the mounts, and then there is the maintainence issue.

Earplugs for those in the pilothouse?

 

[psneeld]

charles wrote:
If it aint broke dont fix it. There will always be plenty of "things" to fix.
Actually the system that is on your boat is way more substantial than two screws into the stringer on the so called soft mounts---what is on CCRIDER and has been there since 1981 with no problem
Just my anecdotal evidence.

*Some things if they look suspect are ALWAYS better fixed in port....hopefully the port of your choice and better*than out at sea.

 

[Marin]

skipperdude wrote:
It sounds like the boat is just set up that way I think I will just let it go.

Don't know your boat's work history or how hard it was worked but if those mounts did the job all those years*with no problems and they aren't causing you any problems now I cannot think of a reason to change the setup.

If the level of vibration is unacceptable--- and you haven't said that it is--- then there might be a reason to go to something else.* But whatever you did it would be expensive since it would involve modifying the stringers and most likely the block part of the mounts too.* But if vibration, noise, and alignment are not issues, as Charles said, if it ain't broke, don't fix it.

 

[psneeld]

What kind of engine and HP?* 90 percent of the boats out there just have some steel angle through bolted to the stringers with any one of dozens of isolation mounts readily available to support the engine.* Relatively cheap and simple to do with a little knowledge of what's needed.

MUCH preferable to relying on a system that may be on it's last legs orf questionable design and difficult to maintain.

In less than a day for not much more than the cost of the isolation mounts...you could have a much more conventional setup.

 

[Marin]

psneeld wrote:
In less than a day for not much more than the cost of the isolation mounts...you could have a much more conventional setup.

*You think so?* From the photos of the current setup it would appear that to use "conventional" mounts like the ones most (?) boats like ours have he would need to have new block brackets designed and fabricated.* If he just sticks a conventional mount under the existing mount he'll have to cut down the stringers because the engine will sit too high for the prop shaft.

I know very little about the art of motor mounts, so I'm saying all this based just on the what seems to be the logic of what I see in the photos.

The engine mounts on our boat are one size too small.* This was done at the factory on all twin engine GB36s of this vintage because the*next size up*mount would put the header tank on each engine in contact with the underside of the cabin sole.* When we had to have our mounts changed, we looked into using the mounts of the same design but rated for the weight of the engine (and then some). Same mounting hole pattern but the mounts were*a little bit taller to accomodate the thicker rubber.* The only way we could have done this was to either have new block brackets designed and fabricated, or the engine stringers would have had to be cut down.* Either choice was an expensive proposition.

In the end, after consulting with our diesel shop as well as the head of engineering at Northern Lights/Lugger who had a lot of experience re-engining boats, designing mounts, etc. we decided to use the same slightly undersized (for the weight) mounts.* The reasoning of our advisors was that since the original mounts had held up for some thirty years before the rubber had become too tired, we'd get another thirty years out of new mounts that were exactly the same.* So there was not much value in spending a big bunch of money to do something that didn't make much practical sense to do.

Which is why I wonder if the situation on SD's boat is similar?

SD--- Are your current mounts looking suspicious to you in terms of integrity*or are you just wondering why they are the way they are?

 

[Jay N]

skipperdude wrote:
I just found it strange to have the motor hard mounted and for what purpose?

SD

Your mounting setup was the way all wooden fish boats were done for many years.* There really wasn't a need for soft mounts because the wood construction naturally absorbed a lot of vibration.

With the advent of "harder" hull substances (particularly metal), the need for soft mounts grew.

Quick story on my old 40' Ed Monk, Sr. bridgedeck sedan, after repower with a diesel mounted direct to wood stringers, ended up with a vibration near cruise rpm.* Raised the engine, fabricated new mount supports, and installed rubber doughnut mounts.* Result was that the vibration simply moved about 150 rpm, fortunately a little further from desired cruise rpm.* Was probably just lucky because you can spend a lot of time/money and just end up chasing the same vibration to a different place.

 

[Peter B]

Exactly, SD, I am definitely in the "if it aint broke, don't fix it" camp, also.

 

[psneeld]

Marin wrote:psneeld wrote:
In less than a day for not much more than the cost of the isolation mounts...you could have a much more conventional setup.

*You think so?* From the photos of the current setup it would appear that to use "conventional" mounts like the ones most (?) boats like ours have he would need to have new block brackets designed and fabricated.* If he just sticks a conventional mount under the existing mount he'll have to cut down the stringers because the engine will sit too high for the prop shaft.

I know very little about the art of motor mounts, so I'm saying all this based just on the what seems to be the logic of what I see in the photos.

The engine mounts on our boat are one size too small.* This was done at the factory on all twin engine GB36s of this vintage because the*next size up*mount would put the header tank on each engine in contact with the underside of the cabin sole.* When we had to have our mounts changed, we looked into using the mounts of the same design but rated for the weight of the engine (and then some). Same mounting hole pattern but the mounts were*a little bit taller to accomodate the thicker rubber.* The only way we could have done this was to either have new block brackets designed and fabricated, or the engine stringers would have had to be cut down.* Either choice was an expensive proposition.

In the end, after consulting with our diesel shop as well as the head of engineering at Northern Lights/Lugger who had a lot of experience re-engining boats, designing mounts, etc. we decided to use the same slightly undersized (for the weight) mounts.* The reasoning of our advisors was that since the original mounts had held up for some thirty years before the rubber had become too tired, we'd get another thirty years out of new mounts that were exactly the same.* So there was not much value in spending a big bunch of money to do something that didn't make much practical sense to do.

Which is why I wonder if the situation on SD's boat is similar?

SD--- Are your current mounts looking suspicious to you in terms of integrity*or are you just wondering why they are the way they are?

*Yep...I'm sure.

 

[psneeld]

Here's the original post...

Does anyone have this sort of set up as far as motor mounts go?

There doesn't seem to be any vibration damper. the mounts hang over the stringers and seem to be hard mounted with just bolts.

I was thinking of changing the mounts to provide for quiet and less vibration.

I'm thinking if I changed anything I would have to reconfigure the entire mounting system.

The 4 th pic shows the actual mount as far as where the bottom of the engine is mounted to the stringers.

SD

The statement is...." I was thinking of changing the mounts to provide for quiet and less vibration."

So I take that as the owner thinks he should have less vibration and quieter operation.

Considering how few people have ever seen the setup he has....hard to say that a more modern setup for rec boats wouldn't give him what he wants and if willing to do a little research and do the work himself...it can be done for a very modest cost.

A lot of people on the board talk about upgrades before anything is actually broke...even if it is...they just don't replace in kind.* So why is this any different?* Maybe because many have never done this kind of work or would be afraid to tackle it?

 

[FF]

http://www.aquadrive.net/

One of the more interesting things about this system is it MUST be out of alignment , or the CV joints wont get lubrication.

Years ago the didn't bother to mention that in the install papers , so we lined everything up.

BAD MOVE , it lasted under 100 hours , but the drive folks made good , and we put bend in the setup.

 

[skipperdude]

I wasn't really having an issue with the way the motor was mounted.

It was just that I read a lot about new motor mounts. and was thinking about after 38 years perhaps it was time to change mine.

The system was nothing like anything I have seen on any other boat. I thought that new mounts would make a difference in the*noise level. It isn't really that loud.*A normal conversation is easy aboard the boat.

I have inspected it closley and It isn't broken. So I am just going to leave it alone.

Thanks for the input I know now more than I did.

And thats a good thing.

SD*

 

[Codger2]

skipperdude wrote:
It was just that I read a lot about new motor mounts. and was thinking about after 38 years perhaps it was time to change mine.

_______________________________________________________

I believe this is a "syndrome" whose cause just might be the various forums and magazines on boating. I've experienced this from time to time & made changes to my boat that were not warranted. One example was when, in Passagemaker magazine, Bill Parlatore was on his fuel polishing kick which escalated into a "water polishing system." I installed a fuel polishing system that I now know wasn't needed.

When the seeds of fear are sewn, (My boat sinking because I didn't do something I read about in a boat rag or heard at the yacht club)* the first symptom is usually feeling a "lightening of the wallet."

I've been trying to come up with a name for this disease but as of now, I have none.

Any ideas?

-- Edited by SeaHorse II on Tuesday 24th of January 2012 10:19:00 AM

 

[skipperdude]

Gottahaveitis

SD

 

[Marin]

charles wrote

By the way, I am the guy who changes fuel filters every 200 hrs without fail, done this for over 25yrs on CCRIDER and never had a clogged filter. Never.

Almost without exception , when I suggest this, I get all kinds of excusses NOT to do so.

*

Not from me you won't * I have yet to meet a mechanic--- aviation, marine, automotive--- who has said that clean oil, clean fuel, and clean filters are bad for an engine.* So I do everythng I can to ensure every engine we own always has all three.


-- Edited by Marin on Tuesday 24th of January 2012 02:30:33 PM

 

[Codger2]

charles wrote

By the way, I am the guy who changes fuel filters every 200 hrs without fail, done this for over 25yrs on CCRIDER and never had a clogged filter. Never.

******* I change mine every year whether I used the boat a lot or not.** Same for the oil filters. Most of the time my fuel filters are still pink, with no trace of contamination. The oil filter or the oil for that matter isn't even black. The mechanic says I'm wasting my money and I probably am but my engine seems to love it!
*

-- Edited by SeaHorse II on Tuesday 24th of January 2012 02:50:15 PM

 

[Peter B]

The oil and oil filter Walt - maybe, as sitting around even with light use does see some chemical degradation in oil etc. But the fuel filters?...yup...definitely wasting time and money there Walt. How often do you (or your garage) change your car fuel filters...? Even Marin admits, with much higher usage than your boat, his fuel filters look fine - when he throws them away...

 

[Marin]

Peter B wrote:
Even Marin admits, with much higher usage than your boat, his fuel filters look fine - when he throws them away...

They do, you're right.* But in the overall scheme of things filters are virtually free so they all*get changed every time I change the engine oil, which has a target interval of 100 hours but sometimes goes out closer to 150 hours. The Lehman manual calls for an engine oil change every 200 hours.

I don't want*one schedule for one thing and a different schedule for something else.* The injector pump oil has to be changed every 50 hours but that's too soon for the engine oil and filters.* So I do everything else on the 100-150 hour interval.

A lot of people think this is far too short of an interval.* I dont care and what they choose to do is irrelevant to me and our boat.* Until the day an experienced mechanic tells me that fresh oil and clean filters are bad for an engine I will continue to follow our chosen intervals, expecially since the cost is not even a blip on the radar of boat ownership.

 

[Peter B]

Fair comment, especially re the comparative costs, but thinking in purely practical terms here - ie in terms of how these things work, and Steve D'Antonio has mentioned this in articles in PMM - what about the known fact that filters actually work better - ie do what they are meant to do a bit more efficiently, when they have been in use for a while, and are actually 'partly clogged' with the stuff they are filtering out...?
Sorry, we have drifted off the motor mount thread topic a bit here, but I think we are mostly agreed the SD would be best to leave his motor mounts alone, as they will probably do another 20 yrs. I know I'm leaving mine well alone.