do i really need to bolt my engine on?

[ajs73]

Hi all.

I've managed to find a 15hp mercury 2 stroke for my 3.2 honwave which i am pleased with. On reading the manual it says that you should bolt the motor to the transom as well as using the normal clamps. I can see the sense in this but is it really necessary - interested to get you views on this!

Regards

Adam

[jamie.rib]

I've never had a problem, I do check on a regular basis on a run.
Jamie

[Ribtecer]

I have a rope for my 9.8 Tohatsu with a stainless clip on the end fixed to the transom just in case.

But I have wondered about what damage it would do with a spinning prop if it came loose.

Toby

[Bigmuz7]

My current AUX is just clamped, but I have a stainless shackle onto a transom eyelet just in case because it does get a bit of a thrashing

[Peter_C]

If you are not going to use bolts, then tie the two tightening lever deals together so they can not loosen. Also on your transom in the middle of the engine plate on the inside you should see a place to clip something to the boat. Rig a cable or sturdy rope from the motor clipped off to this loop. That is so in case the motor comes loose and flies off it is still strapped to the boat.

I searched for photos but couldn't seem to find anything for tying the outboard to the boat but did find this one showing ONE way to tie the clamps together.

[colcreate]

I can only speak from experience, on two occasions I have very nearly lost an outboard overboard after relying on just clamp bolts alone. On both occasions I have been 'exploring the limits' of hull and motor in adverse conditions..... well it's what ribs were made for!
On both occasions the motor's shifted (read all but fell off) and were only saved by the soldered battery cables and control cables! I have also dived on and recovered a manual start Johnson for another 'enthusiastic' owner who clearly decided not to bolt.
Locking the clamp handles together is good advice but it's suprising how things can shift after a bit of water lubrication and a day or two of enthusiastic use.
A tether line is good insurance for a tiller steer but is no substitute for a proper through fixing.

[Poly]

If you plan to leave it on permanently then I would bolt it (mine is) as its one less think to worry about, and one extra hurdle for anyone who tries to nick it.

If you plan to take if off each time then Peter_C's advice above seems right. I'd also suggest that if relying on 'toggle screws' ideally you want a clamp plate (or the top of the transom) which has a lip that would mean the clamps have to really move out for the motor to slip.

[ajs73]

thanks for the replies all.

before i do the 'right' thing and bolt it on, does anyone know what the transom is made of on a honwave sib? if it is solid material then presumably there is no need to put sealant round the bolt holes to stop water ingress?
The engine wont be removed every use but probably on and off every couple of days when we are on holiday.

[Poly]

ajs73 - if you plan to take it on and off more than once or twice a year, I wouldn't bother, never mind every few days.

Not sure what the transom design is - but it would be unusual not to need to seal any holes you drill.

[lockieboi]

Originally Posted by ajs73

thanks for the replies all.

before i do the 'right' thing and bolt it on, does anyone know what the transom is made of on a honwave sib? if it is solid material then presumably there is no need to put sealant round the bolt holes to stop water ingress?
The engine wont be removed every use but probably on and off every couple of days when we are on holiday.

If your taking it on and off I wouldn't worry, just clamp it on tight, secure the thumb turns together with something like a cable tie (that's what ive seen the RNLI do on there inflatables) and tie a rope to the OB and to the transom.

That's what I do with mine and I've never had trouble.

Would be a pain to assemble and dismantle if you've got to undo bolts.

The transom will be marine ply and possibly coated in fibreglass.

If you do drill it I would seal it with sikaflex.

[Dhf]

Mate of mine made a big mistake when new to powerfull outboards, he purchased a real good second hand tiller 25hp yam, eager as a beaver to get out, thought tightening them hand clamps would do,,,, well they did for 5 min then after 20secs on the plane the outboard jumped off, ripping the tiller out of his hand and the motor literally jumped about 4ft out the water, then span around a few secs on the surface before sinking, I was watching from the shore and it looked crazy, It was lucky the dory type hull continued planning before the motor landed.
Not saying bolts are needed with smaller OB's though, my 4hp aux is just clamped.

[9D280]

In total contrast to the above, i have used a 25 on clamps only for years. It did however have the lipped clamp plate as per poly's post and had the clamp screws lashed every time.

[chewy]

Make sure that what your clamping it too is suitable. The previous owner of my fishing boat fitted a stainless plate, whilst it looks the part its also very slippy as my engine made a bid for freedom the other day.
Its only a 6hp but I'll be sticking a couple of bolts through anyway!

[Ribtecer]

Rather than cable ties I use a combination padlock, dual purpose...

My Avon has a moulded fixing plate with a lip around the edge which is a good idea.

[Max...]

I really would not bother bolting on a 15 onto a leisure SIB (except maybe for security reasons).

As for the clamps failing - hard to imagine how they would not hold it 100% securely - someone mentioned their's worked loose after a couple of days extreme use - this is user error really, you should be checking and re-tightening (if necessary) them all the time. I just reach down and check each one every now and again while driving the boat. And as others have said you must install a tether from the engine carrying handle to the transom plate ring.

If you do decide to drill then the Honwaves use an encased wooden transom so you would need to use a marine sealent, good practise regardless.

[Max...]

Just to add, (not sure - I think Honwave have a plastic transom plate inside) but on the Zodiac there is a serrated cast plate on the inside and a softish plywood plate screwed to the outside of the transom - this allows the rear of the outboard bracket to bite into the wood which helps a little I guess...

[Searider]

Just to throw something else into the mix - whilst cable tying or lashing or padlocking the clamp ends together will prevent them unwinding it won't allow for any compression of the transom after the motor is first fitted.

Check the clamps for tightness each time the boat is used - and possibly during the day also.

[Starovich]

Originally Posted by Ribtecer

I have a rope for my 9.8 Tohatsu with a stainless clip on the end fixed to the transom just in case.

But I have wondered about what damage it would do with a spinning prop if it came loose.

Toby

Seen it happen twice, engine falls to bottom off rope and stalls out. As long as you don't have a gorilla at the helm with a strong enough grip to hold the surprise weight of the engine.
If you do, the engine stalls out with the gorilla pulled to the shoulder in the water over the transom.

[9D280]

Originally Posted by chewy

Make sure that what your clamping it too is suitable. The previous owner of my fishing boat fitted a stainless plate, whilst it looks the part its also very slippy as my engine made a bid for freedom the other day.
Its only a 6hp but I'll be sticking a couple of bolts through anyway!

Yep, been there too...

Suffice to say good old wire rope steering doesn't let it fall too far, but i can assure you it won't stall at WOT...

Cast plate with a lip. Much less pain in the long term.

[Ribtecer]

What length of tether is best, short to stop it going to far, or long to let it get far away from the boat before it stops moving?