Outboard HP Reccomendations

[Tsuru]

We have a AB 9.5’ Alumium RIB with a 5 HP honda. The RIB is a great size and handles well.
The only problem is that we don’t have enough power to get on a plane.
Can anyone suggest what size outboard to reliabely plane with my wife and I?
Thanks,
Ray

[Sparx]

From experience 8 hp Yamaha two stroke does the job. Boat cruises on plane at 2/3 throttle with two adults on board.

I recommend 10 hp minimum in a modern four stroke.

[s/v Jedi]

I recommend the max. HP as stated on the dinghy identification plate. When it doesn’t plane with that you need a different dinghy but don’t put a bigger motor than the dinghy is rated for on the transom

[Cheechako]

I'd go with the 9.9, but you may as well get a 15 as it's the same engine usually.

[Montanan]

Highly recommend installing plane lifters to the transom

References:

https://www.maximarine.com/products/lifters/index.html

https://www.youtube.com/watch?v=xrIehHGrEW0

[a64pilot]

Originally Posted by Cheechako

I'd go with the 9.9, but you may as well get a 15 as it's the same engine usually.

and also a 20 HP. Tohatsu and Suzuki anyway.

Even max for the dinghy isn’t often overpowered by any means, and if I my Dinghy said 15 HP max, I ‘d buy the same weight 20 HP.

But really need more info, how many people, and which dinghy? It’s possible that it’s overpropped and putting the correct pitch on will help greatly. I’m against the little wings etc put on motors to lift them, it works, wings do generate lift, but it’s more efficient to simply sit further forward as opposed to lifting the rear, it’s the dinghies with consoles that have to had the wings, seating position if fixed then and you can’t correct an aft CG by moving forward.

The reason you see so many people with extension handles on the tiller is so they can shift the CG forward so the dinghy will plane and ride flat.

[mikedefieslife]

8-10hp should see you plane nicely with two people on board. Probably around 11Knts, and 15-17knts solo. You likely have bigger tubes than my 3D tender. I had to install a big hydrofoil to get up onto the plane 2-up with 8hp, but my older dinghy with 42cm tubes would plane all day 2-up without.

Considering a 5hp engine isn't light anyway, you'd do well to get a Tohatsu 9.8 2 stroke if available in your country region. These are cheap, and are the lightest engine in their class. The 15hp Tohatsu is heavy as it's the same block as the 20. Same with the Yamaha 10hp it's the same block as the 15hp so heavy.

The two most common engines I see around at the Tohastsu 9.8hp 27kg, and the Yamaha 15 Enduro at 36kg. The non-endruo Yamaha is likely a better engine than the enduro model.

[Alistair242]

Suzuki have both 2 stroke and 4 stroke 15hp engines.
The 2 stroke weighs in at about 33kgs.

[Tsuru]

Thanks all for the info. The general consensus seems to be 10 hp without much weight penalty for going to 15.
Thanks again,
Ray

[s/v Jedi]

Originally Posted by Tsuru

Thanks all for the info. The general consensus seems to be 10 hp without much weight penalty for going to 15.
Thanks again,
Ray

Are you sure? I went and looked up the specs and it says max. 15 hp and I think that is what most would recommend in case of a 2-stroke. For a 4-stroke you get into a choice between 8 and 20 hp as the 10’s and 15’s are the same motor as the 20hp. I would go for the 8 in that case, certainly not the 10 at 100lbs.

A 2-stroke 15 is hard to beat for your dinghy.

[Tsuru]

No, I'm certainly not sure, and haven't fully made the decsion. You are correct we are rated for 15 hp.
I like the idea of a 15 hp 2 stroke, but don't know if you can purchase them in the US. We are in Washington State can I purchase new?
Again, I appreciate the help,
Ray

[JimsCAL]

No, can't get new 2 strokes of that size in US. Option would be used.

[a64pilot]

Your pretty much stuck with four strokes being the only option as new, and I believe everyone’s 9.9 to 20 HP is the same motor and right at 100 lbs. at least the Tohatsu’s and Suzuki, Yamaha and Honda are I believe even heavier.

[s/v Jedi]

The Yamaha 9.9 is 87 lbs but Tohatsu has an 9.8 at 81.5 lbs.

The 15hp are all at 100 lbs like the 20hp’s.

[LLCoolDave]

I bought a used dinghy, the hp rating was 10 but the owner put on a 15. Same motor with a different carburator. The extra hp caused cracks in the aluminum near the transom after only a few years of use. I'd recommend the max hp but I wouldn't go over.