Boat won't plane

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I had a question put to me today, by a colleague who bought a boat and motor from two different dealers.

The boat is rated to 15hp and 3 passengers.

But with 2 passengers ( average size) and lots of gear the weight comes to less than 3 x 75 kg passengers.

Yet the boat will not plane - not even close. Just sits flat in the water.

Apparently with one passenger it will plane.

Is this normal? Surely if a boat is rated to 3 passengers and 15 hp it should "work" ( plane).

All teh solutions ( like a new prop) seem to be a very expensive " why don't you try this".


Any ideas? Take up tennis instead?

Gary

[NQCairns]

Hi Gary, Aint physics a b**** sometimes, a boat needs to make enough trust to overcome all the forces acting against it. Without running a prop that can spin fast enough to create this thrust it will do exactly as you state. I would have thought the Business the motor was purchased from would have had more "boat smarts" and offered you a prop that was suited?. At the moment you are running semitrailer tyres on a mini minor. Check around for a second hand prop. If proped right boat will be much more fun to own even 1 up as a bonus. good luck nq

[Kerry]

Might be expecting a bit much based on those specs as it's certainly not going to be a world beater and really imagining the length/size it might be (with 15HP max) one might be expecting a bit much to even get up and over the low 10's hump ?? with a full load.

Cheers, Kerry.

[Gorilla_in_Manila]

Gary,
I've got a 12 ft brooker v nosed punt that would get on the plane with a 15hp merc, standard prop, 3 up and gear around 300kg. Took a while to get out of the hole but would do it. Two up and gear it would get up on the plane no worries.
Who mounted the motor? Assume its close to right height.
Cheers
Jeff

[Brett_Finger]

Gary,
stick a foil of sorts on it,this should make a big differance!
"Stingray" seem to be a brand that works.

and rember because the boat is rated for X amount of people/weigth does not mean a thing about top speed/plaining ability , just the amount of weight the hull will safley handel without being overweight causeing loss of freeboard height / stability etc..
Hookin,Brett

[Jeremy]

If you are interested in a foil Gary, I just happen to have one for sale. Lazilus two piece foil - I believe it is the one recommended by the outboard guy in Bush anf Beach May issue. Rated for motors up to 50 hp. I used to have it on a 30. Asking price $20. Perfect condition.

Jeremy (Brisbane)

[propdinger]

sent you a pm gary

[joeT]

Perhaps try redistributing the weight around the boat. I used to have a 3.75 allycraft with a 15hp and it wouldn't plane with 2 people unless the other person sat in the middle and not at the front. Small boats can be a bit picky with weight distribution.

[gif]

Thanks Guys

great advice and especailly thanks to Jeremy.

I love this board!


Gary

[gif]

thanks all - some goodadvice here

Gary

[Brett_Finger]

Gary,
had a look at the "LGM" at work yesterday,she's a ripper !
i am getting one as well now. ;)
hookin,Brett #;D

[ba229]

i'm the same as the gorilla. 12ft brooker with 15hp marniner (89 model).

this thing planes no problem with 2 adults and gear. i'm 100kg and my mate atleast 80kg. fishing gear would be 30kg.

is the motor reaching full RPM?

[grinder]

just a thought and this is a cheap way to maybe find out what could be the prob check to see if motor is too far down like make sure your cav plate is in line with the hull as recomended by most manufactures they will say raise your motor for optiomin revs and reduce drag but you may find you will have cavitation it is a trade off 4 $$
but it will let you know if it is the prop

Grinder