Serious Outboard Question -Size

[MapisM]

[ QUOTE ]
I want to retain remotes and steering which will get tricky with 2 motors on a small boat.

[/ QUOTE ]That's a good point, tricky it may be, but feasible in principle.
There are leverage systems to connect the wing to the main engine, allowing the wheel to operate both.
But of course the "temptation to be naughty" would still be there!
...actually, I saw this as one of the pros of this solution... /forums/images/graemlins/grin.gif

 

[[2068]]

I'm describing my boat, which is almost 30ft overall, and has a higher hull speed.

And the running away "reaches 25kts without touching the throttle" is exactly the problem. The torque is rising beyond the hull hump speed, so a few more revs, a bit more thrust, which leads to more revs, and a bit more thrust ... ... ... 25kts! Diesels don't work that way. The torque peaks in the mid range, and then falls away.

The trick is to match the engine torque curve to the hull characteristics to get the overall package to do what you want it to do.

I still think that with either a 4 stroke 30hp engine or some trim tabs, you could run that hull at 12/13kts without the adverse side effects.

dv.

 

[hlb]

Twat, why do folk want to be regimental. It's crap, thats what I said and agree. Yes my friend. My boat will do 10 knots if I ask it. All day long. Not sure about 11 or 12 knots though. never tried. Yes I can keep it to any speed, by up and down on the throttle all the time.

>Ten knots is nigh on impossible for any boat

Wrong! I can do 10kts in the S28, so why can't you?

It's a cr*p speed to do, though, superchargers whirring away, ar&se stuck in the water, huge wake being thrown, 40litres an hour for no progress, but it can be done.

dv.



What a crap statement, you sort of disagree then agree. /forums/images/graemlins/confused.gif

 

[[2068]]

>Twat, why do folk want to be regimental.
In your regiment, you'd turn up for parade wearing a dress shirt, combat fatigues, one brown boot, and one black one, then say to the RSM "Twat - It keeps me warm, what's the problem?"

Lakey's hull is much smaller and lighter, so sticking to lower speeds shouldn't be "nigh on impossible". I can't prove it, but a different setup should get him closer to being able to stick to 11/12 kts rather than shooting off in to the distance at 25kts.

dv.

 

[Kawasaki]

My first boat was 16.5 ft Dory type with a cuddy.
I experimented with variuos size outboards as backup.
3.5 would move Her about, cept when the Straits were running at top whack.
An 8 would keep Her pointing against the Full Ebb.
15 got Me anywhere I wanted.
WOT was about 12 not quite planing.
I know Lakey aint gonna face those kind of currents/ tides.
Just pointing out My experiences.
The Hull was heavy and old.
Probably a bit saturated as well.
Steering.
Trying to steer with the main engine whilst the little uns were "fixed" ahead was no good.
Using the little un whilst the big un was "fixed" was much better.
Using the 15 on it's own, connected to the Teleflex was ok too.
Opted for a long shaft 5 in the end.
Anything bigger was too clumsy and heavy to haul on and off.
The 5 would get Me to shore if things went wrong with the main.
Luckily only ever proved in experimental mode.
Twas 1985 and Suzuki had a lovely 3 cyl jobbie.
Stuck a new one of those on.
What a good engine that was.

 

[MapisM]

[ QUOTE ]
I still think that with either a 4 stroke 30hp engine or some trim tabs, you could run that hull at 12/13kts without the adverse side effects.

[/ QUOTE ]Well, if you find any engine or other trick capable of making a 15ft planing hull to cruise with a proper attitude at 12kts, you'd be onto something unknown to the boating industry, imho. All the best!

 

[Lakesailor]

15hp seemed a good bet to me. They are in a lower price range to the 20/25 motors and would just about do the trick.
We'll see.

 

[nyx2k]

my 14ft dejon will plane with 10hp (just) with one on board. and its easy with 15hp and 2 on board

 

[alb40]

10 - 15hp seems a best bet. As you say, alot cheaper than 20 - 25hp engines, which would be too powerfull.

I used to own a Shetland 535. With a mercury 9.9hp engine, it would do about 6 - 7knots WOT, which was perfectly fine for use on the river medway, where the speed limit is 6 knots. A 25hp Evinrude proved too lively, as it would plane with that engine.

 

[Lakesailor]

Shetlands are probably a bit heavier than my boat, but I wouldn't want to be WOT at 6 knots. Far too noisy. You can imagine that a 3 cylinder 2 stroke at 1500rpm is actually very quiet.
I would like to maintain a tranquil experience. It's starting to look very much 15hp.

 

[alb40]

Yes, going along at WOT most of the time wasn't exactly quiet!

As you say, 15hp looks like the way to go. A four stroke one would make cruising quite peacefull in addition to helping keep your speed more steady.