How can I get my rib to plane?

[eyespy999]

Hi there

I am new to boating, recently bought a rib which is 2.7m with a 6hp short shaft 2 stroke fitted with dolefins.

It goes quite well on the plane with just me in it but with two and even three passengers it just chugs along trying to plane.

The rib is rated to a 10hp but was wondering if a slightly bigger engine or a change of prop will do the trick?

Any advice appreciated.

Thanks

[lockieboi]

Stick 10 horses on it!
It still may not plane with 3 though.

[Redknight]

You probably need on average about 7hp per 100kg to plane, so with 3 large people you would probably need more like 20hp...

[willk]

First question: Have you a RIB or a SIB? If it doesn't have a hard hull, it's a SIB. I'm guessing you have a SIB? If so, is it a Slatted deck or Airdeck? Answers on a postcard pls and we'll see what we can do for ya.

[m chappelow]

Removing the doelfins will gain you a couple of knots
They may give the stern lift but you also cause drag especially with a small engine.

[eyespy999]

Thanks all for your replies.

Its a brig falcon 275 with a hard hull and rigid deck. I have a 1997 merc 2 stroke 6hp.

I have read mixed review about the dolesfins if anyone has good advice whether to keep the on or take off.

Thanks again

[m chappelow]

Even though they can help on some craft What you have to think is doelfins were designed for much larger engines and only seem to be one standard size,
the surface area drag on say a 40 hp engine is nothing compared to a much lesser powered engine ,
It's only a 2min job removing or putting them back on to see any difference ,
I have known a few small engined doel finners to cut them down in size a little .

[yoyo]

Get a 9.8 twatsoo 2 stroker nailed on the back end and then it will bat along nicely.

[willk]

OK. Yeah, lose the doelfins. You might try playing around with the engine trim position - start in the lowest position and experiment. Move all the weight forward - you'll benefit from a tiller extension - £20 well spent. That said - I don't see you planing with three adults, maybe an adult and two kids.

It would go well with 10hp but I still think you'd be doing well to plane with three adults...

[Fenlander]

>>>with two and even three passengers it just chugs along trying to plane.

Is that you plus two/three?

Anyway as some have hinted... simple fact is a 6hp is too small to shift that many folks on the plane. My experience with a 3m SIB and 9.8hp is very lively with one adult, still planes with two adults or one adult and two children. Go above that and it struggles.

Ideally if you want to carry that many folks you need a 3.2m-3.5m with 15-20hp. If you have to keep the 275 then this is the ideal combination...

http://www.looking4aboat.co.uk/%5Cdo...0-15-56-27.jpg

For me doelfins are mostly used to try and correct an outboard/craft/weight issue. Get the outfit right and they are not needed just adding drag as said above.