What size outboard

Hello
The boat in the pics is 14ft.
apart from two seats and gas tanks it is empty.
Has anyone any idea what 2 stroke outboard would be suitable?
Apart from two people and some fishing gear,and maybe a 12v battery,that will be
the most it carries.
I need the boat to be able to plane and cruise at 1/2 to 3/4 revs.Top speed is not important.
The outboard leg required is 15" to 16" to suit the transom height.
It has steering and cable controls.
All in all the boat is pretty light in weight.
Minimum and maximum engine sizes would be appreciated.
The boat is for inshore sea fishing.
I am in the UK

 

Many 14" boats can reach 20+ knots with that load and a 20 hp OB. What do you mean by 1/2-3/4 revs? If the maximum is 6000 rpm, do you mean 3000-4500 rpm? A 20 hp will likely be able to plane at 4500 rpm, maybe even at 4000 rpm. You need a much bigger OB to plane already at 3000 rpm. You would probably need 40 knots top speed to be able to plane at 3000 rpm. That would require 40-80 hp depending on your boat.

You say it is "pretty light". Less than 200 kg?

 

A typical 25-30 hp would give you a margin, imo. Cruise at 4000 rpm at 18-20 knots approx. with a standard prop. Unless it is unusually heavy.

 

At a guess,I would say closer to 300kg.
I have an 18hp Evinrude on it at the moment,only tested it on one trip out.(in freshwater)
It put out a large wake,lifted the bow slightly but wouldn't plane.
The prop was a 9.25"X11".I have put a new 9"X9" prop on it and not yet tested it.
I have since purchased a rev counter.
With the larger prop on it,there was no speed increase from half to full throttle,just a larger wake.
The manufacturers WOT is 4500rpm.
Although I have got the 18hp running sweet,I am trying to decide if a slightly larger outboard would be a better bet.

 

Hi Mr E,
I can pull the boat about on the flat when it's on the trailer fairly easily.
I think,like you say,25hp to 30hp would probably give me a reasonable margin.

 

300kg is heavy for a stripped-out 14' runabout. 225 kg is about as much as I'd have expected.

 

30hp would be a good choice, imo, because there is a bit of a jump in weight if you go to 40hp. And price !

 

It's only a guess,you are probably nearer to it than me.
There's not much weight in it,it's got a covered bow,and a splash well.
It's construction is pretty good.(single skin above the deck)

 

I would think that the UK has some regs for this type of boat and it would have a "Capacity Plate" listing limits of HP (or KW), no. of persons, etc.

 

For security reasons and the fact that I have to take it off the boat after each trip a lighter motor is what I had in mind.
30hp sounds favorite.

 

There's no i.d. on the boat,I can't even find out who manufactured it.
I would like to know purely out of interest.
It's been around a while I think,and has been looked after.

 

I don't know the boats in UK market at that size, but around here new 14' boats weight 140-350 kg. The heavier ones have full inner module and lots of details. The simpler ones are around 200 kg.

Your boat is far from new. In the 70's and 80's the weights were 140-250 kg. Also your boat seems to have quite shallow V-hull. If that is correct, I would have guessed it planes already with 10 hp OB (light load).

As a child I had a 14' aluminum boat with 10 hp Mercury. The top speed was 17 knots and it planed easily with 2-3 children on board (40-50 kg each). With 20 hp its top speed was 24 knots and it planed with 5 adults on board at 17-18 knots.

Your Evinrude 18 is very old (60's or very early 70's). Those were rare already in the 80's. It also seems to be clearly too deep in the water, but it is difficult to see exaclty from your pictures. The anti-ventilation plate seems to be way below the keel.

Unless your boat is exceptionally heavy, your engine must have lost its power or you are doing something wrong. It really should plane with 18 hp. How much load do you have? Where do you have the load?

I looked at an old test from 1971. Evinrude 18 was tested on a 180 kg 14' boat. Top speed was 19 knots with two on board. 5000 rpm with 3-blade 9x10 propeller.

You asked advice for a 2 stroke engine. The old 25-30 hp 2 stroke engines are most often the same as 20 hp ones (e.g. with a different carburator). The real power difference is often minimal. There are some exceptions like Yamaha 30 3 cylinder model, which is much more powerful than the older 2 cylinder model. Some of the old 40 hv models are not that heavy. Tohatsu is very light. Yamaha 40 3 cylinder is very good and weights about 70 kg without trim.

 

Just to point out that If you want a 2 stroke outboard they have not been able to sell new ones in the UK since 2007.
The requirement for a plate on a UK boat (I believe, but am not sure) came in with the CE regs in 2005.

 

The whole evinrude range are 2 stroke alive and well in te uk