Bit of a stupid question...

GaryD · 26 June 2006, 22:36

As the title says, its a bit of a stupid question...

Without knowing the kind of a boat, how heavy on the fuel would a 3.0l 4 cylinder 135hp mercruiser inboard engine be as aposed to a 90hp 4 stroke honda outboard?

Does the 135hp inboard give similar consumption to a 135hp outboard?

Been looking at new boats and wondering if the inboard is gona give hellish consumption compared to a 4 stroke outboard...

Cheers

nik · 27 June 2006, 18:53

Hi Gary,
Unless the inboard is a diesel, I can see little point in going for an inboard.
Firstly you lose space in the boat. Secondly, if you dont like the engine or need to change it, it will be much easier with an outboard.
Nick.

paul tilley · 27 June 2006, 20:22

whats the difference in price between an inboard and outboard of the same power including installation

Hugh Jardon · 27 June 2006, 21:16

the price of boat configured to take an inboard, the inboard itself with leg compared to the price of a boat and outboard

what you would lose if you had an inboard...seats or usable space needs to be considered

as mentioned below the amount of room you would lose on a small boat would probably be substantial

the weight of the two options might be a major consideration as well

and then the resale, would others want a small boat with a petrol inboard

outboards are well proven, petrol inboards can be an expensive pain

personally i would stay outboard and would go inboard on a larger boat to get a diesel

i have a honda 90 4 stroke outboard, love engine, very economical and quiet but if the boat would take it i would go for the suz 140 personally if 4 stroke was denf required

Rogue Wave · 27 June 2006, 22:08

It is my understanding that an inboard is more economic than an outboard for the same HP

ADS · 27 June 2006, 22:13

You can get an imported American Bayliner/ bowrider type thingy new for under £12k and these all seem to be fitted with inboard petrols, good value for money methinks (closet hard boat owner

)

Nos4r2 · 27 June 2006, 22:33

Quote:

Originally Posted by ADS

You can get an imported American Bayliner/ bowrider type thingy new for under £12k and these all seem to be fitted with inboard petrols, good value for money methinks (closet hard boat owner

)

Have you seen the shit those things are made of?

There's a web page I saw(that I can't find right now) showing structural damage from hurricanes and what these so called 'composite hulls' are made of.

Essentially one layer of CSM, 1 layer of woven roving and a shitload of FILLER.

I'll post the link when I find it.

ADS · 27 June 2006, 22:41

Quote:

Originally Posted by Nos4r2

Have you seen the shit those things are made of?

There's a web page I saw(that I can't find right now) showing structural damage from hurricanes and what these so called 'composite hulls' are made of.

Essentially one layer of CSM, 1 layer of woven roving and a shitload of FILLER.

I'll post the link when I find it.

Dunno where you got that idea from Nos I always thought they were paper mache!! There are some horror stories, but they do seem to last, and if your only going out for the day and mainly inshore probably would be all right, im not talking about a circumnavigation here! The drives and engines seem to have been around for a while though, so I assume the majority of problems have been ironed out. I know of some horror stories from apprentices at sunseeker too though, not posting them cos someone will sue my ass!

Nos4r2 · 27 June 2006, 22:47

Found the page:-

http://www.yachtsurvey.com/Fiberglass_Boats.htm

Guess what I won't be buying.

ADS · 27 June 2006, 22:51

Quote:

Originally Posted by Nos4r2

Found the page:-

http://www.yachtsurvey.com/Fiberglass_Boats.htm

Guess what I won't be buying.

After looking at those pics, I think I will give these boats a miss!

Nos4r2 · 27 June 2006, 22:54

Its quite scary isn't it.

fast fred · 28 June 2006, 06:15

outboards drink about 1.2 gals an hour at WOT for every 10hp.

Narcosis · 28 June 2006, 06:57

Quote:

Originally Posted by fast fred

outboards drink about 1.2 gals an hour at WOT for every 10hp.

Please don't say things like that, it scares the hell out of me, enough to go and sell my RIB now. According to the above, my Yam 60 2s will drop 45 ltrs of fuel in so short a time that I can't even have the bottle to quote it.

Is this accurate?

I now 2strokes are famous for being heavy on fuel but not at the rate of an alcoholic rugby team.

Pete7 · 28 June 2006, 08:26

Quote:

Originally Posted by Narcosis

Is this accurate?

No, thankfully. Fred is in the US so different sized gallons. You would be better working on 1 gallon an hour for every 10 hp, (so 27 LPH) but this is at flak speed so during a normal day you will use less.

Pete

Hugh Jardon · 28 June 2006, 08:33

i think freds post is very accurate if petes is as his reference is us gallons which seem to be around 80% of a uk gallon

1 uk gallon = 1.2009503853213334 US gallons

1 uk gallon = 4.546092 litres

1 us gallon = 3.785412 litres

i think my opti is rated at using 18 or so us gallons per hour at full chat, but usually you dont drive everywhere at full chat, drop back to 75% or so and you can halve your compsumption or drastically reduce it anyway

reading figures for fuel used at wot is always very scarey, dont get too alarmed by it

smartcraft seem to read in us gallons so giving the impression they are thirstier than they really are

my 200 opti seems to average around 4.3 miles to a us gallon if that helps

jgrace · 28 June 2006, 08:37

Quote:

Originally Posted by Narcosis

Is this accurate?

Not for my outboard it's not!

Full speed on my 60hp Yamaha is 30mph. It drinks roughly 1 litre every 2 miles. Therefore, it uses 15 litres total per hour or 2.5 litres for every 10hp.

I don't know if Fast Fred is using US gallons or standard gallons, but either way I don't agree with him:

Converting from litres, my outboard uses 0.66 US gallons or 0.55 standard gallons per hour per 10hp.

Either way, roughly half of the 1.2 gallons quoted by Fast Fred.

Pete7 · 28 June 2006, 10:28

Quote:

Originally Posted by jgrace

Full speed on my 60hp Yamaha is 30mph. It drinks roughly 1 litre every 2 miles.

Yours is a 4 stroke isn't it ?

Pete

fast fred · 28 June 2006, 11:34

thats for Flat out, bolted to the floor, for one hour. some will do better
others not.

jgrace · 28 June 2006, 14:50

Quote:

Originally Posted by Pete7

Yours is a 4 stroke isn't it ?

Pete

Yes it is. Sorry, was this all about 2-strokes? Fast Fred just said "outboards"

Jim

jgrace · 28 June 2006, 15:12

Quote:

Originally Posted by fast fred

thats for Flat out, bolted to the floor, for one hour. some will do better
others not.

The figures I've been quoting are average consumption. I've never tested my consumption flat out, but I reckon it's probably better than average, because the boat is planing the whole time. Fuel consumption per distance is much heavier in displacement mode, and as most of us spend a significant amount of time getting in and out of harbours etc. at slow speed, it follows that this will make the overall consumption worse.

Jim