motor mount idea....looking for input

[oops!]

hi all.....

im just about to glass in my motor mounts.....

one of the things i have been thinking of is to install a thin rubber pad between the motor mounts and the hull.

the mounts will be glassed in place solid...so they wont move...the rubber is just there so any noise/sound vibration will not travel thru the mount beam and to the stringers and thru the hull...

there is pics of it here ...post # 1867

on posts 1870....ther is a potential problem pointed out by an i boats member..........1871 is a rebuttle......

this is a new idea....is there anything i havent thought of ??? and any other potentially un seen problems from a technical end?.....

as allways....thanks your input is allways muchly apperaceated.

http://forums.iboats.com/showthread.php?t=234392

cheers
oops

 

[Fishermark]

Re: motor mount idea....looking for input

It looks like you are getting 76 pages of comments on the project over there.... That's probably the better place to keep this type of discussion.

With that said, since you asked... ... It seems to be a non issue to me. I can't see it making a bit of difference in vibration. But that is simply my non-educated guess.

 

[oops!]

Re: motor mount idea....looking for input

thanks fishermark.....and yes it is a resto question....

but i posted here because building the boat is just one part....

the mechanical is another part...i need mechanical advice just in case i havent thought of somthing from a mechanics perspective...

there is a detailed explanation on post 1877

thanks
oops

 

[NelsonQ]

Re: motor mount idea....looking for input

I'm no expert but using the rubber to dampen noise between the hull and the mounts, with the mounts glassed in place shouldn't cause any structural or support issues for the engine. Its simply an insulating layer.

 

[oops!]

Re: motor mount idea....looking for input

that is exactally what i am trying to do....thank you for explaining it properly.....

(im really tired.....work all day then on the boat till midnight every day to beat the winters comin clock) !

 

[NelsonQ]

Re: motor mount idea....looking for input

that is exactally what i am trying to do....thank you for explaining it properly.....

(im really tired.....work all day then on the boat till midnight every day to beat the winters comin clock) !

Heck oops, we'd work well together then. I don't think I could ever do what you've accomplished in your resto so far but I can talk about it
I totally understood what you were saying (had a hard time understanding the pic, but your description was bang on) You deserve being tired with the efforts going into it.

 

[QC]

Re: motor mount idea....looking for input

I was waaaaay confused until I realised something, those aren't motor mounts . . . I would call them motor mount BEDS. What you will mount to the beds are motor mounts . . . and those should have rubber bushings in them . . .

I am not sure whether what you are considering will hurt or help, but I think you need to consider checking in over here. This is Glen-L and they sell the plans for my Monaco . . . There is a forum and these guys have considered a lot. There are also "Newsletters" that may address exactly what you are thinking although there is not a lot of fiberglass info, mainly wood and epoxy . . .

 

[oops!]

Re: motor mount idea....looking for input

thanks qc......and yes...that is what i mean...(im just beat....need to take some time off)

i have been search ing on there for a while...but havent seen any thing yet....ill keep looking

 

[Bondo]

Re: motor mount idea....looking for input

Ayuh,....

My Motor Mounts have a rubber cushion built into them,.. Aka. factory Merc mounts, circa mid-90s...

I built the motor mount Beds for my tinboat Starcraft using .090 sheet aluminum,+ broke it over in a few angles for the strength,+ pop-riveted it to the hull's ribs.....
Nothing has Moved since the install,.... Pushing 700+hrs....

I kinda think you're Rubber Sheet Idea is maybe the cure for a possibly precieved non-issue.....

Other than that,...
I can only see a possible gimbel bearing mis-alignment if the rubber fails.....

 

[oops!]

Re: motor mount idea....looking for input

i tghink im gonna scrap the idea......just too many iff's....and, as uasual bondo-s 1 sentance answers......speak volumes

thanks any how guys

 

[HT32BSX115]

Re: motor mount idea....looking for input

Your best bet IS using the OEM mounts for your engine/drive combination. The rubber "snubbers" in the OEM mounts are designed to move no more than required for that engine/drive combination.


I read thru your restoration thread....... Whew!

I'd love to see it when it's all done!


Nice job!


Cheers,


Rick

 

[JustJason]

Re: motor mount idea....looking for input

I've used dynamat in the past and it works pretty awesome. I don't know about sandwiching it in. But you can use the dynamat underhood insulating foam under the engine box to quiet that down. It probably wouldn't hurt if you used dynamat extreme on the inside of the transom area as well.

 

[Lou C]

Re: motor mount idea....looking for input

I agree with those who say, use the OE mounts the way they were designed to be used, mounted to a rigid surface. If the surface the mount is attached to is cushioned, the mount may move more than intended affecting alignment and causing problems down the road. Plus if the rubber contracts or settles, that also can affect alignment or transmitted vibration.

 

[JustJason]

Re: motor mount idea....looking for input

you can always lay dynamat down everywhere but not directly under in the motor mounts

 

[45Auto]

Re: motor mount idea....looking for input

Glad Bond-O got to you and talked you out of that idea! You want those beams mounted as solidly as possible to the structure of the boat. Any vibrations they see should be forced into the ENTIRE HULL of the boat. Allowing the mount beams to move independently (even a little tiny bit - small movements mean high frequency) will gradually weaken and crack the glass and allow water into the wooden structure as you use the boat. Mounting them solidly will allow the entire hull to act as a vibration damper for any vibrations that make it past the vulcanized rubber motor mounts bolted to your engine block.

 

[wca_tim]

Re: motor mount idea....looking for input

If you're worried about vibration noise, there's dynamat to help some, but you can also get a pair of the anti-vibration mounts that were used on the non-balance shaft 4.3 v-6 engines for a while... they should hold up fine since they really only support the weight of the engine - the transom takes the torque load.

I would be leery of doing anything but making very strong structure under the mounts. Mine are layered mahogany bonded and stacked with filled epoxy resin - inside the original cloth / resin assembly that was still very sturdy...