Inboard vs. Outboard for Cruising

[brianlara 3]

Originally Posted by Cadence

Take all the low HP things with a grain of salt. I doubt some people know how to figure there flat water speed with no current or wind?JMHO

It's easy. Just look at the plotter screen. S.O.G. = speed over the ground. Updated every second or there abouts.
Where does "grain of salt" come from? Year now is 2016....satellites!

[SV DestinyAscen]

Of course it is possible. Just depends on your expected sailing conditions, personal preferences and risk tolerance.

I've said this a lot in the electric propulsion threads. If you only need to motor out of marinas and anchorage and have the flexibility in schedule and personal risk tolerance necessary, yes even the rudimentary outboards setup will do.

But for most people, I think a good threshold for margin of safety is capability to motor for 48 hours.

In catamarans you'll be more likely to find good outboard systems with fuel tanks external to the cabin, properly ventilated and in appropriate pods forward enough to minimize ventilation/cavitation. They're also more likely to have the real estate for a robust solar setup that mitigates need for charging house banks.

[boatman61]

Originally Posted by Cadence

Take all the low HP things with a grain of salt. I doubt some people know how to figure there flat water speed with no current or wind?JMHO

Easy Peasey..!!
Walk to the bow and toss a cork float ahead of the bow.. as you reach it hit the stop watch.. or start counting.. as it reaches the stern you've so many seconds.
Quick calculation of time by boat length gives you the speed.. or use a chip log.

[brianlara 3]

Originally Posted by SV DestinyAscen

Of course it is possible. Just depends on your expected sailing conditions, personal preferences and risk tolerance.

I've said this a lot in the electric propulsion threads. If you only need to motor out of marinas and anchorage and have the flexibility in schedule and personal risk tolerance necessary, yes even the rudimentary outboards setup will do.

But for most people, I think a good threshold for margin of safety is capability to motor for 48 hours.

In catamarans you'll be more likely to find good outboard systems with fuel tanks external to the cabin, properly ventilated and in appropriate pods forward enough to minimize ventilation/cavitation. They're also more likely to have the real estate for a robust solar setup that mitigates need for charging house banks.

My 135 watts does virtually nothing to contribute to SOC. The charging of my 480ah comes from a 60A charger powered by 2kv gen. 50 hours motoring @ 5 kts on flat water. 45L external tank.
All configuration differ. Mind you, I'd love a hi thrust Yammie but motoring is very low priority.

[tuffr2]

Typically a rule of thumb...if you are thinking between two engine...say 9.9 vs 15, the bigger engine will be the right choice 80% of the time.

[Cadence]

Originally Posted by brianlara 3

It's easy. Just look at the plotter screen. S.O.G. = speed over the ground. Updated every second or there abouts.
Where does "grain of salt" come from? Year now is 2016....satellites!

SOG is great but says nothing about what is propelling the boat. Look up grain of salt. I am not sure it doesn't have a biblical origin?

[thomm225]

Originally Posted by smj

Hanging of the stern of a monohull, I'm pretty sure the outboard would have cavitation or ventilation problems.
Sent from my iPhone using Cruisers Sailing Forum

Totally incorrect.

The 5 hp outboard which is mounted on the stern of my boat for the last 5 years has never had a problem with cavitation or ventilation.

Furthermore, it does every bit as well as the diesels that were on the boat before the outboard was installed if not better.

[smj]

Originally Posted by thomm225

Totally incorrect.

The 5 hp outboard which is mounted on the stern of my boat for the last 5 years has never had a problem with cavitation or ventilation.

Furthermore, it does every bit as well as the diesels that were on the boat before the outboard was installed if not better.

I wasn't trying to be negative, just passing on my experience with an older mid 60's Cal 28 with an outboard in a well. I'm completely pro outboard where the installation makes sense.


Sent from my iPhone using Cruisers Sailing Forum

[SV DestinyAscen]

Originally Posted by brianlara 3

My 135 watts does virtually nothing to contribute to SOC. The charging of my 480ah comes from a 60A charger powered by 2kv gen. 50 hours motoring @ 5 kts on flat water. 45L external tank.
All configuration differ. Mind you, I'd love a hi thrust Yammie but motoring is very low priority.

Yah... I think most good designers consider the entire package - and IMO the flaw with gasoline outboard isn't the usual criticism about dangerous gasoline (it can be safely stored if done right like any fuel) but from a systems integration POV if you need a genset or engine to recharge batteries, why carry two fuels...

I think that's why so many good sailing light catamarans use outboard gas engines because they don't need battery charging because they have 800 watt panel systems.

[brianlara 3]

Originally Posted by SV DestinyAscen

Yah... I think most good designers consider the entire package - and IMO the flaw with gasoline outboard isn't the usual criticism about dangerous gasoline (it can be safely stored if done right like any fuel) but from a systems integration POV if you need a genset or engine to recharge batteries, why carry two fuels...

I think that's why so many good sailing light catamarans use outboard gas engines because they don't need battery charging because they have 800 watt panel systems.

Exactly.

[newhaul]

I have an 8hp tohatsu 2 stroke outboard with 80 watt alternator hat lives in the lazzerette well that was designed for the motor to be lifted out of the water and laid sideways in the las when not needed for long voyages. No issues with cavitation . As far as exhaust issues that is solved easily by having an engine that exhausts below the waterline just in front of or thru the prop. I get about half a gallon per hour at 5kts sog, same as I got with the 4 stroke Honda that I had before on this same boat.

[thomm225]

Originally Posted by newhaul

I have an 8hp tohatsu 2 stroke outboard with 80 watt alternator hat lives in the lazzerette well that was designed for the motor to be lifted out of the water and laid sideways in the las when not needed for long voyages. No issues with cavitation . As far as exhaust issues that is solved easily by having an engine that exhausts below the waterline just in front of or thru the prop. I get about half a gallon per hour at 5kts sog, same as I got with the 4 stroke Honda that I had before on this same boat.

Strange.

Your boat only displaces 4200 lbs whereas mine displaces 6600.

I can cross the 20 miles of bay here in 3-4 hours with my 5 hp 4 stroke outboard and only use a gallon or so

[barnakiel]

It can be done with an outboard. Boats that sail well need only minimum help (at times none at all) from an auxiliary propulsion (e.g. an engine). Some sailors use oars too (on smaller boats, say up to 30ft or thereabouts).

Look at the Pardeys, or, more recently, at Webb Chiles.

In some areas (plenty of currents, little wind) or/and in some boats (heavy cruising tubs) you cannot really do without an engine.

So the answer is, I think, 'YES, but'.

A good sailor in a boat that sails well, in areas that do not pose immediate threat to a boat that runs out of wind, does not need an engine. Unless he is married.

b.

[newhaul]

Originally Posted by thomm225

Strange.

Your boat only displaces 4200 lbs whereas mine displaces 6600.

I can cross the 20 miles of bay here in 3-4 hours with my 5 hp 4 stroke outboard and only use a gallon or so

Actually I estimate my boat to be more like 5500 to 6k disp. the way I have her outfitted

[brianlara 3]

Originally Posted by thomm225

Strange.

Your boat only displaces 4200 lbs whereas mine displaces 6600.

I can cross the 20 miles of bay here in 3-4 hours with my 5 hp 4 stroke outboard and only use a gallon or so

Not so Thomm. Firstly I motor at only 60% throttle load.
Second. My boat weighs abt 6,500 lbs normal weight.
38 litre freezer
480 ah agm batt
170 litres fuel
150 water.
A 35lb manson on bow, 25lb on stern.
Bow chain = 250 ft @ 5/16" stern chain 26ft 3/8"
Loads of power tools, 60 amp batt charger, inverter, 2kv generator, Springfield Ladderback helm chain on a transverse slide and 360 deg swivel, bread maker, 60 days of good food half of it frozen, 20lb and 10lb propane bottles..and on &on.
Believe me now?