Auxillery size?

[NQCairns]

Hi, I am looking to find out how big an auxillery would need to be to push a 16 to 18 or so footer at around 10 knots (appprox 20km) at about 80% throttle? Any ideas appreciated. How fast does yours go? Thanks NQcairns.

[littlejim]

not exactly what you were after; but- I've got a 6HP on a 15 foot f/g runabout, gives me about 6mph flat out. Have got my moneys worth out of it many times when the big motor had solenoid problems.

You probably want to go a bit bigger, but it will also depend a bit on how far from home you go. If a big storm is coming up you may want to go a bit faster than 6mph.

[NQCairns]

Little Jim, thanks for taking the time to reply, so you get about 1MPH per HP. Nice to be self reliant on the water. I have a 30hp that I was thinking of putting on an 18 footer when finished, bit heavy and overkill in the aux area but I was interested to see by how much. Cheers Nqcairns.

[smerl]

I'm not sure about the 1MPH per Horsepower rule. I don't think your 30 hp will push the 18 footer along at 30 MPH!

[Lucky-Phill]

Forgive me for not quite understanding why one would need an auxillary.

I have owned boats since.......well that's a long time now, in fact my mate Noah sold me his old one

If I went fishing / offshore and had that little faith in my one / main motor, I wouldn't go. But maybe I am missing the point here !

I mean, trying to cross our bars in large boats with little motors is a definate no no !

So, why do you need an auxillary , NQ ?