Not really the right seagull?

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AusAnzani
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Re: Not really the right seagull?

Post by AusAnzani »

I agree with B, she's a little high at the moment. Aim to have the caitation plate align with the bottom of the hull.

Max speed is greatly influenced by the hull design. Yours being flat, there is a lot of surface tension which translates to friction. To break that surface tension, you need to get air under the hull. Easier said than done with limited hp, or more correctly said, limited torque.

If you can get the nose up, maybe by keeping as much weight aft whilst you're travelling, you may see a difference.

Theoretically speaking, the more boat you have out of the water, the faster you will go.

Regards
S
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Algordo83
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Re: Not really the right seagull?

Post by Algordo83 »

Collector Inspector wrote:"The higher cooling water inlet is above the bottom of the boat (although still well in the water)and I am no longer getting my nice thick water flow right through the rev range."

Ok do as below and try again......

20171130_121821.jpg

BnC

Hmm. Interesting. I was thinking of lowering it until the inlet holes were both below the hull. I'll try your suggestion. Thanks. :)
Liam2k3
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Re: Not really the right seagull?

Post by Liam2k3 »

What is the pitch on those props?
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Charles uk
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Re: Not really the right seagull?

Post by Charles uk »

11" diameter x 10" pitch.
Make it idiot proof and someone will make a better idiot.
Keith.P
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Re: Not really the right seagull?

Post by Keith.P »

Charles, how did you work out the pitch?
I know you are good at minimal angles, I've seen them, when you open your wallet.
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Charles uk
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Re: Not really the right seagull?

Post by Charles uk »

I didn't Keith, both the other Charles & I discovered when you go to interview people about Seagull history you find some that will say "I was going to throw this paperwork away, but as your interested you might as well take it".

The moral of the story is, if you don't talk to people you get nothing.

This was taken from a report about a series of drawings of current Seagull props in 1986.

So I didn't have to spend an hour calculating it!
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headdownarseup
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Re: Not really the right seagull?

Post by headdownarseup »

This reply is directed at Nudge as he asked the question, but join in if you like :P It's good to share info

For my particular heavy(ish) 17 foot GRP day cruiser (semi planing V hull) with a wspc gull on the back and a hydrofan prop fitted, with this set up the boat was dreadfully slow. I could probably walk quicker it was THAT slow. I thought there was something wrong with the engine when i tried it like this :cry: So much so that i tried 3 other hydrofan props just to make sure it wasn't a rogue prop with different characteristics somehow. All of them slooooooow. Quite gutless actually.

With a weedfree prop fitted to the same wspc it was transformed, plenty of go in it, overall speed was probably damn close to hull speed at 2/3rd throttle. Wide open throttle just makes more noise with no appreciable gains in speed but with reduced fuel economy.

In essence there will be all sorts of variables going on here, but the way the motor was mounted onto the transom as vertical as i could get it, set at the correct height, load evenly distributed inside the boat etc everything was peachy with a weedfree prop. I couldn't have wished for a better set-up on my boat.

With a different boat the hydrofan prop would probably behave completely differently again, more akin to how you'd expect it to be, but for my boat a hydrofan prop is no good. Don't know why. It is what it is.

Curiously i don't get any bother at all with any of my 102's on the same boat. I've even tried mounting the motor well off to one side to see if the keel was masking the way the water flows around the gearbox/prop. No difference, the boat still reaches close to hull speed around 6mph. Swept back or bowtie, cloverleaf and meat cleaver props all seem to behave quite similarly on my boat no matter what type of 102 or century i'm using at the time, (not including bargepusher 102's here as they're just slow any which way you look at them) but for some reason that i can't explain my boat doesn't like any kind of hydrofan prop. I'm now starting to experiment with some later gull boxes/props. EFNR boxes with corresponding props etc. with some pretty good results. They don't seem to be faster or slower than anything i've tried previously, i'm just looking for a more user friendly set-up that will work well enough for what i use a boat for ,which primarily is canal cruising and open reservoir chugging on fishing trips ,often at slow trolling speeds but with enough oomph to cope with a stiff wind when the need arises.

As with all different shapes and sizes of boats there's bound to be a lot of differences, some are harder to explain than others as to why they would work better or worse.
Something else i can't explain why, but an elderly bone stock AC 102 with a swept back prop that i've used quite a lot will out perform this wspc of mine even with its weedfree prop. Not by much, but it does go just a little bit faster for some reason. Don't know why or how but it does. We're probably only talking 0.5mph faster, but faster is still faster. Go figure. I'm not a racer you understand, so pretty much all of my motors are bone stock. Sure they've been apart before, but i've not done anything to them to enhance their performance from the engine. Not really. About as far as i go is to polish the gearbox and prop (where applicable) and make sure the prop is equal in every way across all of its blades. A lot of work, but i think it's worth it.

I can imagine that to some of the newbies choosing which seagull best suits their boat it can be a bit of a lottery at times, suffice to say i think you should try and match the motor to the boat as best you can,not too big or too small for a given size of boat, then try and fine tune things as you go. Experiment with some different props if you're brave enough, or leave things as BS intended and just enjoy the seagull for what it is. Rugged and dependable, and at times a pain in the.........




Jon
Algordo83
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Re: Not really the right seagull?

Post by Algordo83 »

So...
Lowered until the plate is in line with the bottom of the hull, fitted some 'silencers' (a hose clamp around each exhaust tube hole and some air filter sponge over the storm hood)

It's much less choppy and much quieter , although still loud. My cooling water flow is back to a good stream.

I sit in the middle with my tiller extension (length of pipe ) and just let it get on with it. :) enjoy the pootle.

Speed : 8km/h at half throttle. 8.5km/h at full beans. So no point revving it up and wasting juice . Ha.

Well. That will do. It's better than rowing and its enough to make progress against the tide here, just about. :)

Until I get my boat license the seagull will do fine.
And then I'll keep it as a backup for those bigger boats I will inevitably get. :)

And when i have my boat license the ten foot will get a 20hp 'frothblower' and skim over the water like a thing possessed. Seagull enthusiasts look away. Ha.
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Charles uk
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Re: Not really the right seagull?

Post by Charles uk »

Al
I suggest you try to borrow a Hydrofan prop & get yourself the essential measuring tool (a wrap around the HT lead digital tach from ebay, it will cost about the same as a meal for 2 in Mcdonalds) & will measure exactly what the motors doing, without giving an answer that is affected by the wind & tidal flow.

Seagull's Hydrofan props were claimed by them to give up to a 10% improvement, it might not be quite as much as that, but a lot of those Kiwi Seagull racers use them & many do an awful lot of research, I think that might have prompted Nudge's question, he must know what he's doing as he won his class on the Waikato, the Hydrofan probably has a fraction more pitch than the weedfree, as you'll find your going a little faster at the same revs, but is easier to spin so you'll see increased revs at full tilt, I admit they're horrible looking & love collecting weed, but borrow a clean one & let us know how you get on.

Jon's answer was probably distorted by his boat, a tinny like yours probably weights 200 K fully laden, whereas Jon's boat probably 4 times as much, the fact that Hydrofans are not prone to slippage as much as the weedfree, could possibly mean that his motor bogs with the Hydrofan but slips with the weedfree allowing the revs to increase (more bangs per minute equals more power) even if some of it is just making bubbles.

Air is the most difficult thing to get into a Seagull & any form of restriction to air flow, won't help, Seagull boats run faster when running almost level, unless on the plane, so the tiller extension is a good idea (but make sure it can't slip out accidentally),
if the smoke & noise offend you buy a Honda.
Make it idiot proof and someone will make a better idiot.
Algordo83
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Re: Not really the right seagull?

Post by Algordo83 »

I'll see if I can source a hydrofan to try out. Thanks for the advice :)
Actually I am rather suprised by how little smoke there is! My strimmer produces more smoke. Perhaps this is because the exhaust has to come up through the water. I don't know, as I say, I'm not that experienced in boating.
The noise is ok now I've covered those two little holes. That and the thin bit of sponge I've fastened over its nostril must be reducing performance a little, but I can't detect it. Those holes must be there for a reason (and not just to produce an ear splitting crackling )

Today's trials produced 9.5kmh WOT with the tide and 7.5km/h against it. So let's assume a 1km/h tide at that point in the river and I'm at 8.5km/h WOT. That's just me , in the middle, boat fairly level. If I sit at the back I lose the ability to cruise at half throttle.

Yep. Special 'non falling off' bit of pipe tiller extension. It's tied on with a wire that also wraps around the throttle so I can shut off the motor if i need to by twisting it. But there's not really much danger . I can get her up to full tilt and swing the motor fully one way or the other without much happening . Just a tight turn. I once lost control of a small RIB on the plane. The tiller shook out of my hand and the resulting tank slapper flipped the whole thing over! Not much chance of that. Ha ha.

I think this motor will never be able to get my tinny to plane. Its just not designed to do that. Unless I made a ported, nitrous injected, expansion chambered seagull and upped the gear ratio by about 400%
But I won't. Ha ha. No point. As you say. I might as well buy a Honda..
(Well, actually I'd buy a Chinese outboard Yamaha 4hp clone, as they are only $299 brand new delivered off ebay.... ) [But since im poor as, I won't/cant :) free boat, free motor remember ]

Point is... I am having fun.
headdownarseup
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Re: Not really the right seagull?

Post by headdownarseup »

To be able to obtain a boat AND a motor for £0 these days is bloody good going. Well done that man.

Just to clarify what i was saying earlier with props, my boat is HEAVY. Yours by comparison is light-weight and probably will glide along much easier than mine. A hydro-fan prop on your little tinny will more than likely be much better than my set-up, but as boat hulls all vary quite a bit there will be good points and bad points with all of them. I'm not looking for speed with my set-up, i'm more into user friendliness these days and trying to stay faithful to the seagull brand rather than going to a "foreign brand" :roll: . If i wanted to go fast (and i mean REALLY fast) across the water it'll probably be with something over 100hp if i could afford it, but as i'm poor like you a seagull ticks all the boxes very nicely thanks.

If noise bothers you, try ear defenders. (whip off the air filter sponge and uncover the 2 holes and you might go a little bit faster still)
Noise is good, smoke is good (up to a point). If others start pointing fingers at you, raise middle finger of right hand and salute back at them.
It's your motor after all.

Jon
Algordo83
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Re: Not really the right seagull?

Post by Algordo83 »

images (1).jpeg
I'm having another look at that advert and really taking in what it says. Things like 'heavy loads ' , 'up to 4 or 5 knots ' , 'huge slow moving propeller ' and particularly 'not suitable'


It just turns too slow. Using a vehicle analogy. Seagull made this motor to slowly move dump trucks. But it's a Fiesta motor with one really low gear.

I've put it in a fiesta and expected it to go quicker. But it can't because it's still in that low gear. Max revs is 8km/h. Dump truck or fiesta.

There's likely enough power in that motor to spin that prop twice as fast or more on my boat and exceed hull speed.

Now...40's are geared different. It says so on those ads.
I bet the 40 will move my boat a little quicker, despite the smaller prop and less power, simply because it spins the prop faster.
Or if it only moves it at the same speed, It will do so using less fuel. Plus it's 10 pounds lighter, which is a bonus.

So.. Next time I'm up at the Father in law's I shall fettle that little one back to life and try it out. I'd be interested to know the results.

Watch this space

:)
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Charles uk
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Re: Not really the right seagull?

Post by Charles uk »

Al, I won my first Seagull race in Port Chalmers NZ, with the girl friend's father's long shaft silver century plus using a cleaned up hydro fan, in a 10 ft, plywood dingy at nearly 12 Mph & got my picture in the Otago Daily Times.

According to Seagull's own dyno figures, long shafts have 0.1 bhp more than short shafts of the same model & the 40 series produces exactly half the horse power of the silver centurys.

In fact Seagull's dyno is in my garage, but I can't work out how to calibrate it.

If you do the calculations from the data in the drawing I posted you will see that with zero prop slippage you would achieve 2.08 knots (2.36 Mph, 3.77 Kph) per thousand engine revs!
Make it idiot proof and someone will make a better idiot.
skipper20
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Re: Not really the right seagull?

Post by skipper20 »

I think you have the answer in the Silver Century Plus brochure you posted. It says in part that the motor is suitable for sea-going displacement hull craft 16-20 feet. NOT suitable for light dinghies. You have the latter. Yes, I would see if your FIL will swap your Silver Century for that 40 Plus you saw in his shed. It seems to be the more logical motor for your 10' boat.

Bill in Seattle
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