Big Boats and Outboard Power...

[w32honu]

Hello Everyone,

Just signed up and curious whether there are any of us out there using small outboard motors as auxilliary power. If so........how effective and what size outboards for what size boat?

I know it may seem a common question, but I am in the process of designing a modification (o/b well) to push a 12,000# boat. The result will be a dramatic simplification of my systems. A huge increase in storage capacity. And would lighten the load a bit...........and improve my sailing performance.............

The intended use would be just to manuever in and out of port and in close quaters. All of the study and theory regarding h.p. and prop pitch......etc is fine. But it is the real world application that I am curious about. And so I turn to you good people.

Thanks in advance,

s

[s/v 'Faith']

This idea has worked out well on many boats with suitable hull types.

Take a look at James Baldwin's site, specifically;

The Inside Outboard

I have an outboard in a well, and LOVE it for the same reasons you listed.

[Pappy Chris]

I have a Luger Voyager Ketch 30' and displaces 9800lbs. It has a 15HP Evinrude electric start and remote controls. It's been used primarily as you've outlined. I had occasion to use it in 40kt wind on my beam going back to the marina. I motor'd about 4 miles at 1/2 throttle and had no problem. I have motor'd 3 miles to weather with no problem at all with it. It's proven to have ample power to push the boat whenever I've called on it. All Kansas lake sailing -- Chris

[beau]

Make sure you get a "high thrust" outboard, which has a bigger prop and lower geared

[w32honu]

Faith,

Thanks for the post guys. Curious what size o/b you are currently using in your well.

And thanks for the link. I have had the opportunity to talk with James Baldwin in the past. Definately some good ideas...........

Detracters would argue that there would be an exponential loss in ability to motor. This may be true. But I am most curious about the degree of loss and thus the trade off for increased sailing performance and all of the other benefits previously mentioned. I guess it is just a matter of priority.

My attempt here is to get an idea of the amount of displacement vs the amount of h.p.

Thanks again,

Cheers

S

[beau]

the general rule is 5hp per ton for displacement speed.

[SkiprJohn]

Over the years I've used outboards and inboards in various conditions. For your stated purpose an outboard in a well would be a fine idea. For at sea in rough conditions I would prefer an inboard.
Here are some of the problems I've noted lately using an outboard on a Columbia 28, a Folkboat 26, a Wharram 23 cat and a WWP 19. Gas fumes below decks, raising and lowering the engine to keep the prop leg clear of the water while sailing and reaching the controls while steering the boat. If you can design your well with enough vertical space to raise and lower the outboard and close off the hole in the bottom of your boat as well as keep fumes from leaking into the cabin and have remote engine controls you will have a pretty great system. An electric start 10 hp 4 cycle would be all you'd need for the purpose you stated. Of course, you could get a larger engine if you want but remember the raising and lowering problem and weight of the engine.
regards

[anotherT34C]

I've sometimes wondered why we don't store our dinghy outboards on brackets that would allow them to function as emergency backup to the inboard.

[Pappy Chris]

The raising and lowering with 1 hand I agree can be a bear some times. Before I decided to sell my Luger I was in the process of engineering a way to use an salvaged tilt trim system from a Mercrusier I/O to raise and lower as necessary with a switch. Even had a design on spring loaded doors to close the bottom of the well when it was retracted. Now its winter in Kansas and I am selling it... no time now to complete it
I did use 2- 3" bilge blowers (1 push 1 pull) and hose to vent the well area out the stern but in Luger's the well is pretty well sealed and separated from the cabin interior anyhow. I have 2 louvered vents on the sides and 2 on the stern.

[Pappy Chris]

Originally Posted by Pappy Chris

I have a Luger Voyager Ketch 30' and displaces 9800lbs. It has a 15HP Evinrude electric start and remote controls. It's been used primarily as you've outlined. I had occasion to use it in 40kt wind on my beam going back to the marina. I motor'd about 4 miles at 1/2 throttle and had no problem. I have motor'd 3 miles to weather with no problem at all with it. It's proven to have ample power to push the boat whenever I've called on it. All Kansas lake sailing -- Chris

Correction. Luger Voyager 30's displace 8800 lbs.

OOOPs!

[marshmat]

An outboard of 5 to 20 hp, on a retractable bracket, is quite a common choice for auxiliary power around here on sailboats of 18 to 26 feet or so.

It's a logical choice for a boat with few systems, low electrical demand and limited space, that will only be under power while in the marina. Some of the common problems- hard to lift up, etc.- can be avoided with balancing springs, clever linkages, etc. A well might be tricky to seal in such a way that the water flow under the hull isn't disrupted, though, and takes up space just like an inboard. I would be much more inclined to just add a bracket on the transom, unless the hull was originally designed with a motor well. Several o/b manufacturers have "big foot" or "high thrust" lines with larger diameter props, steeper gear reduction, and sometimes a better alternator, that are better suited to a sailboat then the standard versions.

The downsides, of course, are that powering in a rough seaway is problematic, and the electrical output of these small outboards can barely keep a battery charged well enough to run nav lights and a VHF. And converting an existing, inboard-engine boat to outboard-in-well or outboard-on-bracket is unlikely to do anything nice to its resale value.