Mounting the outboard engine on heavy duty rubber pad !!!!!!

[phillnjack]

This might sound a bit wierd to some folk out there, but here goes.

Is there any problem in fitting the engine on the transom and putting a heavy duty rubber pad between
engine and transom ?

I ask this as today ive fitted a real heavy duty rubber pad thats 1/2 thick and when tightened the bolts up its squashed down to almost 1/4 inch.
I am thinking that it could help with vibration and also keep the engine from shocking the transom or
causing any damage to transom when tightened up.
Plus its gives a very even load bearing compared to just bolting to the fibreglass.

My boat used to have a real crap piece of plastic on the transom that the makers call a transom pad.
Its just a very flimsy hard plastic thing and ofcourse it broke as soon as i dropped it on the floor.
So in my wisdom i cut a large rubber pad i had lying around for years and mounted the engine with that.

Now tonight im wondering if there is any reason not to have the rubber pad

Any views on this good or bad ???????


phill..

[JohnsonM50]

This might sound a bit wierd to some folk out there, but here goes.

Is there any problem in fitting the engine on the transom and putting a heavy duty rubber pad between
engine and transom ?

I ask this as today ive fitted a real heavy duty rubber pad thats 1/2 thick and when tightened the bolts up its squashed down to almost 1/4 inch.
I am thinking that it could help with vibration and also keep the engine from shocking the transom or
causing any damage to transom when tightened up.
Plus its gives a very even load bearing compared to just bolting to the fibreglass.

My boat used to have a real crap piece of plastic on the transom that the makers call a transom pad.
Its just a very flimsy hard plastic thing and ofcourse it broke as soon as i dropped it on the floor.
So in my wisdom i cut a large rubber pad i had lying around for years and mounted the engine with that.

Now tonight im wondering if there is any reason not to have the rubber pad

Any views on this good or bad ???????


phill..

A few things come to mind, I'm sure its tight but any movement while going could work towards loosening things. The clamps I'd assume are direct or hard contact to the hull, at least the motors thrust won't tend to push them forward as it pushes at the bottom it would pull into the clamps. If its thru boltable I'd advise they be there. The vibration & noise inherent in an outboard will transfer thru the clamps some so it wont be completely dampened. & a question.. how big a motor is this?

[phillnjack]

There is no chance of engine bolts comming loose, these are very tight and i keep a close on this type of thing all the time.
The motor is a 3 cylinder 54ci 60hp evinrude 1995 with power trim and raised as high as the bolts will allow.
Im not realy concerned about vibration but just thought it must be kinder to the transom.

The transom is strong,very strong ive completely rebuilt the boat due to bad transom its in another thread, and the transom is now easily strong enough for a 150hp.
(cannot put a big 150hp on the boat as it would sink ha ha )
The fibreglass outer skin of the transom hull i just thought could suffer from future spider cracks etc and by using a rubber gasket it could benefit the boat by slightly cushioning the engine stresses to transom.

This rubber pad is not a flimsy type rubber,its a sort of cross between a rubber car mat and a conveyor belt.
its proper strong tough stuff and was a nightmare to cut it and drill the holes in it for transom bolts.

I put a small piece in a vice and tried to crush down to see if it would flatten out, not a chance of flattening it.


phill

[JohnsonM50]

There is no chance of engine bolts comming loose, these are very tight and i keep a close on this type of thing all the time.
The motor is a 3 cylinder 54ci 60hp evinrude 1995 with power trim and raised as high as the bolts will allow.
Im not realy concerned about vibration but just thought it must be kinder to the transom.

The transom is strong,very strong ive completely rebuilt the boat due to bad transom its in another thread, and the transom is now easily strong enough for a 150hp.
(cannot put a big 150hp on the boat as it would sink ha ha )
The fibreglass outer skin of the transom hull i just thought could suffer from future spider cracks etc and by using a rubber gasket it could benefit the boat by slightly cushioning the engine stresses to transom.

This rubber pad is not a flimsy type rubber,its a sort of cross between a rubber car mat and a conveyor belt.
its proper strong tough stuff and was a nightmare to cut it and drill the holes in it for transom bolts.

I put a small piece in a vice and tried to crush down to see if it would flatten out, not a chance of flattening it.


phill

Looks like you thought of everything, the vice test especially. Good Luck

[phillnjack]

Well i think i must of forgotten something as its akll gone back too easy .

I tried the vice to make sure it was not just a waste of time and effort, as if it was going to simply crush then
its not going to be much good.
At the top of the transom is a small piece of alloy angle that covers the seam, this would of made the engine
slightly off of being on a true flat surface, i think this was the reason for the original piece of plastic.
There dont seem to be any sort of give in the transom to engine mount,i had a good try and bounce it up and
down and left to right yesterday.
No movement and i weigh around 220 lbs, so with a tubby like me hanging and bouncing on it and the engine dont
move it it should be ok.


i just wondered if there was any definite no no's for doing this type of thing, i see many boats with a
wood pad or stainless pad to help stop stress cracks etc,but most of the stainless ones seem to be
put on after the cracks have started !!!!!!!!!!!


phill

[JohnsonM50]

It's the nature of polyester resin/glass & jell coat to be brittle. mostly those are the jel coat cracks but do get worse with time. Trailering can be tuff'r on a boat than driving it, a transom saver type devise helps. On the 1st post I didn't know what you were woking with, your motor has significant bolts so should hold fine. You'll check after running it & see right away if the motor compresses it more, I'd guess if at all the lower part could sqweeze a bit.

[phillnjack]

i will be keeping close eye on what happens and will take torque readings before the tests and during
(with a friend who dont know it yet)
driving the boat while i see if there is any changes in tightness when under full power ha ha .

i was lucky in that there was no bad stress cracks before i done the transom as it was totaly rotten.
But like i say its now a realy strong transom that should hold up very well.

i did have a few stress cracks on the insed of the transom but have fitted stainless steel support brackets
that would hold a battle ship ha ha
these are 24 inch x 3 inch and 1/4 inch thick 316l brushed stainless.
a few people have said they are a bit over the top, but i dont like to take any chances ha ha .
(plus it was what was available at the time and at a good price)


this shows what i mean by large strong transom plates/savers.

[JohnsonM50]

I wouldn't consider it over the top long as it doesn't weigh you down & that isn't heavy.

[David Mason]

I suggest trying leather. Very thick leather, such as 1/4" thick. I use this between the transom and engine mounts on my racing boats that use the 70HP Johnrudes, highly modified. I have the clamp on style mounting. I found the leather to allow the clamps to bite in and not loosen while uner power as compaired to a metal of some sort. Personally I would't try the rubber as you described. Not sure on it without seeing it, but it seems to me that rubber would squeeze to a point then rip if bounced around. I coul dbe wrong as I know there are a million variation and formulas for making rubber.

[phillnjack]

The rubber i used is very much like a piece of leather as in for strength puposes,probably a lot stronger !!.
its got a sort of nylon strand type stuff woven in with it.
its like a very thick timming belt on a car type of rubber, but a bit softer to the touch if that
makes sense .
its impossible to try and tear it, and a stanley type knife blade is a waste of time trying to cut it.
i ended up using a jigsaw to get the shape i wanted.
and then i had to drill it with 3/4 inch drill bit so the 1/2 bolts can go through it,even then they have to be
threaded through as its just so tough.
its very heavy duty and would probably weigh around 40 pounds a square yard.

i am not worried about the rubber breaking up, the engine or boat would have to give in way before this stuff
rips or tears or breaks down its structure.
ive seen similar stuff to this used in horsebox trailer floors,just this is a bit thicker and stronger.
I have tried to stretch it,that was impossible, drilling it is even hard work as its just seems to close up the holes straight away.
But it does squash a tiny bit and i think may give a slightly softer base for the engine to be mounted on.

I just wondered if there was a reason why we dont see more rubber pads and not the silly stainless on the backs of boats.
to me as soon as i see stainless i think its just hiding a rotten transom or huge spider cracks.
Its seems many of todays new boats come with plastic transom pads even for the 250hp rib market !!!!!!

I will definitely be taking a lot of notice how this stuff works or dont every time the boat gets used, i like to keep
my eye on anything and everything possible to do with the mounting of anything that could move,i.e prop nuts,
engine bolts,steering connections, control cable connections etc.
Most other stuff can just fail and cause a stoppage,but anything mechanical comming loose could not only be
dangerous, but could be fatal.

Personaly i would think a rubber pad would cause the mounting bolts to stay tight rather than vibrate loose, they
would act like spring washers to a point.
all the time the bolts are under full pressure there is less chance of them comming loose.

But i am taking peoples points of view seriously, there could be something im not thinking about.
But leather and water is not much good when mounting engines i would think due to shrinkage and degradation.
Leather does tend to tear easy and does fail when used in and out of water compared to a hard rubber material,thats
why its not used much for seals nowdays compared to rubber.

but like i say i do see the reasoning behind statements against rubber, and i am taking it all in .


phill.....