Towing a powerboat

[Superaquarama]

Never had to think about this until now as I bought boat and engine separately, but I'm astonished that it's possible to tow a small powerboat (specifically, Boston Whaler) with a 50 hp outboard (weighing what, 3 cwt / 150 kilos?) hanging off the transom and probably bouncing around into the bargain. How the heck doesn't it tear off the transom ?

Is there anything that can be done to alleviate the situation, e.g. some sort of bar from the rear crossmember of the trailer to the bottom of the outboard leg ? Or maybe the opposite, i.e. a rope to pull in the leg, with a block of wood in the outboard bracket to lock it solid in the tilted position ? Or maybe I'm worrying unnecessarily and need to do nothing at all, as most would seem to do ?

Done plenty of towing over the years but always day sailers with outboards small enough to remove easily.

Thanks,

Anthony

 

[William_H]

Your concerns are correct. Often a large O/B engine is left in the tilted up position for trailering. It is the mass of the leg and prop ona lonf lever to the engine and finally the transom that is of concern. It is not uncommon around here to see a strut fitted from the front of the gear box down to the trailer cross member to support this weight.
Of course many also rely on the hydraulics of the tilt mechanism to support this weight.
Interesting last week I made a post on 3 guys who nearly perished after the transom fell out of their wooden mobo. I will bet the transom while rotten was damaged by the drive to the launching ramp with o/b unsupported. Hopefully most transoms are strong enough to take the bending action of an unsupported o/b but why take the chance? olewill

 

[blackbeard]

Just a thought on this ...
far be it from me to suggest you don't need to support the O/B properly while travelling, but ...

the thrust from a 50 hp engine is going to be, what, about 500 lb? which is roughly a quarter of a ton? and that's the steady load, not the peak of a shock load in a lively sea

so even in normal use you are going to need a STRONG transom

 

[Davegriff]

As blackbeard says the transom of a boat needs to be very strong. I'd have thought if the transom was strong enough for the recommended engine, being on a trailer with the outboard tilted would make little or no difference. Of course, over-engining or a rotten transom is going to give sometime, either afloat or on the trailer.

 

[Rigger Mortice]

The bashing that an outboard/transom gets when a boat is going full chat in a sea way is far more than it gets on a trailer with suspension to soften any impacts.

 

[dunedin]

RIBs certainly get towed many thousands of miles that way without problems

 

[Superaquarama]

Ok, well many thanks indeed for the replies, everyone, and for the reassurance - I think !

I'll have a go at making a strut of some sort anyway, then just trust to luck and avoid potholes.

 

[Andrew G]

The sensible thing is to contact the "right" people to ensure that the various components are designed and constructed to be up to the task:
- is the transom OK for that power and weight of motor?
- is the trailer up to the boat and motor?
- is car towing hitch up to it?
- is the car up to it?
- etc
In a previous 18’ Mo boat of mine there was a support under the motor (100HP) for towing (V8, 5 litre car - I towed and travelled thousands of km). Andrew