outboard motor mounts

[johnny roger]

my current tinny (3.75M) has no engine mounts. am planning to drill 2 holes in the transom to accomdate 2 stainless bolts for the bracket. is this advisable, or do i take it to the boat shop? if i do it myself, what kind of sealer do i use for this application? an am i correct in surmising that i would use nylock nuts? I am assuming that the hole has to be drilled all the way through the transom? also, i have heard that the wood on the outside of the transom that is under the bracket should be a plastic thing, like one of those butchers cutting boards or something.
all these questions...so many questions...:-[
John

[geoffmck]

I have just used silicon in the past with oversized washers and have had no issues. Always used stainless bolts/washers/nuts as well. Under the motor if I needed to lift the height to have the cavitation plate level with the bottom of the boat (or just under) I always used a bit of 25mm x 25mm x 3mm solid aluminium square tube. Just cut the ends on a 45 degree angle so you can drill through and secure each end with an aluminimum rivet.

[TonyM]

For the sealant you should use Sikaflex, in particular you need to make sure it's the neutral cure sikaflex as the wrong version is very bad for tinnies.

For the mounting plate yes it's far better to use a piece of Poly as the wood will eventually age and soak salt water in which will encourage electrolysis. When you put the Poly plate on aim to create a seal to stop water getting behind it. Basically run sikaflex around just inside the whole edge (it will spread when it's secured) and add another few beads in an "X" the the middle. Any excess can be easily cleaned with a rag dipped in petrol before it cures.

Your local plastic welder should be able to supply you with the Poly

Cheers
Tony


I forgot to add, normally there are additional supports welded inside the transom where you'd drill through to mount the motor, if it's mounted purely on the plate alloy I don't think it would last very long....

[johnny roger]

For the sealant you should use Sikaflex, in particular you need to make sure it's the neutral cure sikaflex as the wrong version is very bad for tinnies.

For the mounting plate yes it's far better to use a piece of Poly as the wood will eventually age and soak salt water in which will encourage electrolysis. When you put the Poly plate on aim to create a seal to stop water getting behind it. Basically run sikaflex around just inside the whole edge (it will spread when it's secured) and add another few beads in an "X" the the middle. Any excess can be easily cleaned with a rag dipped in petrol before it cures.

Your local plastic welder should be able to supply you with the Poly

Cheers
Tony


I forgot to add, normally there are additional supports welded inside the transom where you'd drill through to mount the motor, if it's mounted purely on the plate alloy I don't think it would last very long....

Jeez thanks a bunch for that valuable information Tony. I will definately follow your method. When you say that there are additional supports on the inside of the transom, do you mean its a 'V' shape? my transom has such a thing, and it also has a round bar coming from the 'V', and welded to the hull.
John

[TonyM]

Jeez thanks a bunch for that valuable information Tony. I will definately follow your method. When you say that there are additional supports on the inside of the transom, do you mean its a 'V' shape? my transom has such a thing, and it also has a round bar coming from the 'V', and welded to the hull.
John

That's it - normally it's alloy box section in the shape of a V.

I imagine if the outboard is installed correctly on pretty much all tinnies the mounting holes would land over these anyway but figured better safe than sorry! :)

Cheers
Tony

[FNQCairns]

Yeah marine sika is the go, 921, 291 or something like that??, use what you need then stick it in the freezer in a plastic bag (a tip I got from this site) have found it last almost forever then.

cheers fnq

[Outsider1]

Hi Johnny,

from memory the 18hp Tohatsu motor you have is considered a portable i.e. comes with quick release clamps, and is just clamped to the transom rather than being permanently bolted.

Nothing wrong with permanently bolting it on as you are proposing, but just wanted to make sure you knew that.

Cheers

Dave

[johnny roger]

Thanks again Tony.
John

[johnny roger]

Hi Johnny,

from memory the 18hp Tohatsu motor you have is considered a portable i.e. comes with quick release clamps, and is just clamped to the transom rather than being permanently bolted.

Nothing wrong with permanently bolting it on as you are proposing, but just wanted to make sure you knew that.

Cheers

Dave

Dave,
Yep thats right. it has the quick release clamps. the reason why i am adding the permanent bolts is that i have heard storeys where the outboard has come off the back while on the trailer. and if you have ever been to FNQ, the roads can do just that! so just a bit of extra piece of mind really.

John

[TonyM]

Abother option worth considering is to add a chain to the outboard.

I used to have a chain on the outboard in my smaller tinnies for a few reasons. Firstly it would slow down the river rats when they tried to steal the outboard (lived on the river)

Secondly it would save the outboard from going in the drink if for whatever reason the clamps let go.

Worth a thought, although you might be right that mouniting it with bolts is a safer option with the wild roads you have up there (unless you can be bothered to take it off and carry in the car each trip.)

[johnny roger]

Abother option worth considering is to add a chain to the outboard.

I used to have a chain on the outboard in my smaller tinnies for a few reasons. Firstly it would slow down the river rats when they tried to steal the outboard (lived on the river)

Secondly it would save the outboard from going in the drink if for whatever reason the clamps let go.

Worth a thought, although you might be right that mouniting it with bolts is a safer option with the wild roads you have up there (unless you can be bothered to take it off and carry in the car each trip.)

Tony,
I did think about a chain, but then i imagined my outboard bouncing off the back of the transom and dragging along the road or hanging there while driving along.
my boat is kept at home and in the shed. im not saying that that is the be all and end all of outboard motor theft, but again its another peice of mind as opposed to leaving it on the river.
Thanks,
John

[Jock The Rock]

i got my motor padlocked with chain, bolted with four stainless bolts and then i zip tied the quick release tabs together so they cant come undone.

lets just say i dont want to lose it (its my prize possession atm) :)

i was told to use duralec between ur stainless and aluminium u can get it from any marine shop i think.