Will a 10hp motor get my Yam 340S onto the plane?

neil9327 · 14 August 2013, 21:47

I had a 15hp Mariner outboard with my Yam 340S SIB, and it performed well, getting the boat onto the plane, and a top speed of 15 mph.

Unfortunately the engine was stolen at the weekend.

To replace it I would like a 10hp motor, because it might be lighter to carry, and use less fuel. And perhaps a little cheaper.

I don't mind if it is a little slower, but I still want it to get onto the plane. Is this still going to be possible with a 10hp motor?

Thanks

rossymtb · 14 August 2013, 21:53

How many people and how much kit will you be taking with you then we can give you a better answer?

mister p · 14 August 2013, 21:56

Two stroke with no kit in good condition. Of course it will.

rossymtb · 14 August 2013, 22:02

Put this way i had my 3.8m boat, 9.8hp merc, 2 adult and 5 kids (age 5 to 9) it only just got onto the plane against the tide coming back up the river.

mister p · 14 August 2013, 22:06

Quote:

Originally Posted by rossymtb

Put this way i had my 3.8m boat, 9.8hp merc, 2 adult and 5 kids (age 5 to 9) it only just got onto the plane against the tide coming back up the river.

Doesn't matter which way the tide's going.

neil9327 · 14 August 2013, 22:21

Quote:

Originally Posted by rossymtb

How many people and how much kit will you be taking with you then we can give you a better answer?

Just me (72Kg). No kit.

So it looks like a yes then

Thanks all!

Hopefully I won't get my new motor nicked too.

I think I was a bit unlucky with the current one. I had tied my boat up on a disused dredging boat on the Basingstoke canal near Aldershot (UK) specifically to keep it away and partially hidden from a car park adjacent to the public slipway there. I was only gone 2 hours during twilight while I returned to Winchfield to collect my car. The thief had to jump a 80cm gap between the dredging boat and the canal bank carrying the motor at the same time - must have been more athletic than me!
And they had it away with a 3/4 full 50-litre fuel tank too.
I reported it to the police. But I can't expect them to find anything.
It was only an old motor which was a beggar to start. But I had grown a little fond of it <weep> lol

Fenlander · 14 August 2013, 22:25

Bear in mind your proposed 10hp may be the same outboard as your 15hp but with less power... i.e. weighing the same. If you're going to carry the weight of a 15 at least enjoy the power of a 15.

Sunstreaker · 14 August 2013, 22:31

Are you up on the plane on the Basingstoke canal?

neil9327 · 14 August 2013, 22:35

Quote:

Originally Posted by Sunstreaker

Are you up on the plane on the Basingstoke canal?

Well I do confess to giving it a bit of welly once or twice on the trip. But 18mph is a tad over the 4mph speed limit so I didn't do it more than a few seconds.

Apparently the wash from high speeds can damage the banks of canals and rivers, so I kept my speed down..

gridge · 14 August 2013, 22:42

50 litres??? where were you planning to go?

neil9327 · 14 August 2013, 22:44

Quote:

Originally Posted by gridge

50 litres??? where were you planning to go?

A friend bought the tank some years ago.

Bombing around the needles, Isle of Wight I have in the past gone through half the tank in 2 hours or so. Perhaps it is burning fuel a little inefficiently?

At full power how many litres/hour would you expect a 15hp engine to burn?

Sunstreaker · 14 August 2013, 22:47

Are you sure some upset angry narrow boater didn't hide your engine?
No seriously, bad luck,
If your mainly using it on the canals, why don't you go for a smaller four stroke. There may be some advantages.

Max... · 14 August 2013, 22:49

Quote:

Originally Posted by neil9327

A friend bought the tank some years ago.

Bombing around the needles, Isle of Wight I have in the past gone through half the tank in 2 hours or so. Perhaps it is burning fuel a little inefficiently?

At full power how many litres/hour would you expect a 15hp engine to burn?

10% of rated power in gallons per hour at WOT seems to be a safe rule of thumb.

neil9327 · 14 August 2013, 22:53

Quote:

Originally Posted by Sunstreaker

Are you sure some upset angry narrow boater didn't hide your engine?
No seriously, bad luck,
If your mainly using it on the canals, why don't you go for a smaller four stroke. There may be some advantages.

Well who knows.. I guess I could go back to the scene and have a hunt around for it, but I'm not sure it would be worthwhile. I did pass a fisherman a few hundred meters before though.

The only reason I was on the canal was that it was windy down on the solent, and I didn't want to risk having the boat blow over, as has nearly happened in the past.
So the engine needs to be for both inland and offshore use.

The basingstoke canal is a little gem, because it is very little used (I passed only 2 other boats moving) and has few locks (excepting the section near Brookwood).

neil9327 · 14 August 2013, 22:58

Quote:

Originally Posted by Max...

10% of rated power in gallons per hour at WOT seems to be a safe rule of thumb.

10% of 15hp is 1.5 gallons/hour = 6.8 litres/hour

Over 2 hours is 13.6 litres = 26% of the tank.

So my engine was running at around 50% efficiency given that I had used around half the tank.

..maybe it was time to get a new engine then

Sunstreaker · 14 August 2013, 23:01

I got seriously moaned at by someone at the Wey end of the Basingstoke canal cooper of months ago . I was chugging along on a 62 ft NB, I must have been doing all of 4mph. I am having a bit of a four stroke conversion after my recent 2 stroke problems.

mister p · 14 August 2013, 23:31

Quote:

Originally Posted by neil9327

Just me (72Kg). No kit.

So it looks like a yes then

Thanks all!

Hopefully I won't get my new motor nicked too.

I think I was a bit unlucky with the current one. I had tied my boat up on a disused dredging boat on the Basingstoke canal near Aldershot (UK) specifically to keep it away and partially hidden from a car park adjacent to the public slipway there. I was only gone 2 hours during twilight while I returned to Winchfield to collect my car. The thief had to jump a 80cm gap between the dredging boat and the canal bank carrying the motor at the same time - must have been more athletic than me!
And they had it away with a 3/4 full 50-litre fuel tank too.
I reported it to the police. But I can't expect them to find anything.
It was only an old motor which was a beggar to start. But I had grown a little fond of it <weep> lol

Lock it. Lock the handles and if you want drill a hole through the transom and run a cycle lock through that or a handle on the tube. Run a cycle lock cable through everything. They're chancers and scum. Little ferrets. They'll be put off by hassle. If you're not planning on taking the engine off, cover the clamp handles in grease. Stops rust but also puts off the pikeys.

lightning · 15 August 2013, 09:22

If you want a lightweight engine why not get a Tohatsu 9.8?

It only weighs 26kg (the same as a 4hp four stroke) and my Zodiac 2.85m SIB will achieve just under 20 mph with two of us on board, using this engine.

Locozodiac · 16 August 2013, 01:33

At wot, most 2 strokes OB's consumes 12% of it's rated HP per hour. That's with a lightly loaded boat.

Happy Boating

mister p · 16 August 2013, 05:59

Quote:

Originally Posted by Locozodiac

At wot, most 2 strokes OB's consumes 12% of it's rated HP per hour. That's with a lightly loaded boat.

Happy Boating

Are you sure? My 8hp Mariner 2T does 10 litres per hour at WOT on a two man 3m SIB. Planing at 18 kts.