Exceeding the HP rating for a tender?

[davethedog]

Hello all,

We are currently here in the Caribbean and use our tender a lot, along with the 9.8hp Tohatsu 2 stroke OBM we purchased at the same time.

The plate on the aluminium hulled 3D tender we have states max engine power of 10hp, but.....could we exceed this with say a 2 stroke 15 or 18hp OBM as even with the OBM we have when 2 up we can not always get on the plane.

Thanks in advance

 

[Skipper_Christoph]

I think the limitation is more concerning the weight than power of the outboard

 

[Refueler]

IMHO - the main point to take into account is the depth of the prop and its effect on pitching up the bow as power comes on. As long as the motor does not cause undue pitch up - why not - there's always throttle anyway ..

A larger but not too heavy O/bd for tender at lower throttle ? Nicer for others around not to listen a screaming lower power O/bd ..

Plus of course - weight to lift on / off tender etc.

 

[geem]

Hello all,

We are currently here in the Caribbean and use our tender a lot, along with the 9.8hp Tohatsu 2 stroke OBM we purchased at the same time.

The plate on the aluminium hulled 3D tender we have states max engine power of 10hp, but.....could we exceed this with say a 2 stroke 15 or 18hp OBM as even with the OBM we have when 2 up we can not always get on the plane.

Thanks in advance

I have lots of friends in the Caribbean running a 15hp Yam Enduro on an ali tender that says not more than 10hp. The ali tenders are assuming heavy 4cstroke engines. Its worth adding a oversized planing plate to the Enduro 15hp, if you go that way. With the extra performance of a 15hp, the plate will help keep the nose of the dinghy down when running at speed in a good chop. It feels a lot safer

 

[Alicatt]

Some, Suzuki for example, 9.8hp, 15hp, and 20hp engines are the same with just the ECU mapping and a restrictor plate in the airway/exhaust to give you the lower powered engines they use the same 305cc powerhead.

 

[geem]

Some, Suzuki for example, 9.8hp, 15hp, and 20hp engines are the same with just the ECU mapping and a restrictor plate in the airway/exhaust to give you the lower powered engines they use the same 305cc powerhead.

Yam Enduro 9.9 and 15hp are the same engine. Different reed valves only and a jet change in the carb

 

[Alicatt]

Yam Enduro 9.9 and 15hp are the same engine. Different reed valves only and a jet change in the carb

Easy job then, used to modify the 12hp Yamaha DT125 motorbikes to give 17 -19hp, hardest part was knocking the big washer out of the exhaust to derestrict it

 

[Mark-1]

I've always wondered about the wisdom of running my long shaft engines on my tender because there must be more twisting moment than they anticipate for any given power. Doesn't stop me doing it, obvs.

 

[B27]

Too powerful an outboard or one with too long a shaft will make the dinghy want to fold in half, more so if you pumped up the dinghy on a hot day and now it's cooler.

 

[ithet]

I have noticed that some transom tenders have longer rear tube overhangs than others, presumably this is to allow for heavier (= more powerful) motors while maintaining stability.

 

[geem]

Too powerful an outboard or one with too long a shaft will make the dinghy want to fold in half, more so if you pumped up the dinghy on a hot day and now it's cooler.

The OP has an aluminium rib

 

[srm]

On a contract in the Persian Gulf we bought a roomy fibreglass dinghy with a max engine size of around 10 HP to use between base ship and the island we were surveying. Our base ship had a Merc of 20 or 25 HP that we used on the dinghy. Everything went well, planed nicely with three of four up until one day a couple of months later when I used it to collect some execs from our clients and noticed an interesting fountain erupt from the keel under the midship thwart. Managed to get them out to the base ship without incident. Basically, we had managed to break the dinghy's keel without misuse other than the engine and loads carried.

 

[Restoration man]

We had a 2.8 Avon rib deep v version, said 10hp max but fitted a 15hp mercury 2 stroke, 10 and 15 same engine just down rated , went like stink and even pulled a Ringo with adults in it ,

 

[Graham376]

Hello all,

We are currently here in the Caribbean and use our tender a lot, along with the 9.8hp Tohatsu 2 stroke OBM we purchased at the same time.

The plate on the aluminium hulled 3D tender we have states max engine power of 10hp, but.....could we exceed this with say a 2 stroke 15 or 18hp OBM as even with the OBM we have when 2 up we can not always get on the plane.

Thanks in advance

Seems strange, your aluminium hull should be quicker than our 2.9 inflatable which planes at 18 kts 2 up, with the same engine. Presumably, you've tried altering the angle of the outboard? Only worry about oversize engine is, in the case of an accident, authorities or insurers may not be happy.

 

[William_H]

Seems strange, your aluminium hull should be quicker than our 2.9 inflatable which planes at 18 kts 2 up, with the same engine. Presumably, you've tried altering the angle of the outboard? Only worry about oversize engine is, in the case of an accident, authorities or insurers may not be happy.

Hopefully a very remote possibility but as said any accident/ tragedy with a motor exceeding manufacturers plate could leave you liable. Even up to manslaughter. But as said in practical operation all as said above is ok. An o/b power small boat can get into all sorts of trouble in rough water even with regulation o/b size but broached in big waves.
Have been some manslaughter charges (or lesser charges) here against skippers in the case of accident and death mostly related to high speed in dark when drunk. Be careful. ol'will