What size of outboard do I need?

[Carl Frost]

Hi Everyone, I've been carrying out a re-furb on my 20' Springer Waterbug over the Winter/Spring. All going 

good, total re-paint on the outside (almost done!) and loads of other items fitted. The outboard Honda 9.9 hp

(approx 1992) has been rebuilt and is running well. My concern at the moment is the size of the engine against

the weight of the boat (approx 3.5 tons?), during the good weather recently I had a trip out on the Lancaster

and I monitored the fuel used. Travelling 7 hours (3.5 out & same return and 8 miles out & same return) I used

10.5 litres, therefore 1.5 litre per hour approx, fairly windy on the return journey. Does this seem about right

or would a 15hp or 20hp perform better. Maybe similar performance but get there a bit quicker?

Thanks guys, look forward to hearing from you.

Carl. 

[Tony Brooks]

Sounds very good consumption to me. Even with a diesel that are inherently more fuel efficient we reckon 1 to 2 litres per hour.

[rasputin]

Quicker? Will it not push you around at 4mph? 

 

[MtB]

Well a 40 ton narrowboat used to have one horse power....

[WotEver]

1 hour ago, Carl Frost said:

Does this seem about right

Yes

[X Alan W]

If your engine is the Honda 9.9that has the same block as the 15 hp there is a mod you can do to the throttle linkage which if possible will let the throttle open fully & give you  approx 13 hp with no other mods required Bring up Honda 1992 9.9HP outboard on your computer & there is a "U" tube video showing how to do the mod it consists of removing a re stricter screw

[Mike Nicoll]

One of the main issues to consider is the extra stopping distance needed, with this lighter engine.

[Murflynn]

I don't see any need to up-rate the engine - 9.9hp will push it just fine.  Trouble is that most outboards that you buy off the peg are designed to push lightweight boats at planing speeds.  Ideally you want an outboard designed for pushing a heavy boat at low speed - typically as for a sailing yacht auxiliary motor.  These are available in many manufacturers' listings, perhaps you can check the specifications of your motor.  You may get an improvement in thrust if you fit a larger diameter and smaller pitch propeller.  It will also help you stop faster.

[Jim Riley]

I bought a 32ft nb hull with an old honda 9. 9 on it, it was OK but I do like to do river trips and also I didn't think it had enough stopping power. I got a 2012 Honda 20 and put a high thrust prop on it. Its great!

Its also more economical than the old engine and has more electrickery coming out to feed the batteries. 

I don't know if there's a high thrust prop for the older Hondas. 

[Carl Frost]

Hi All, Thanks everyone for your comments, interesting one Jim about the high thrust prop, made a few enquiries about that. Cheers everyone.