trim tabs

[mitc69]

manage to get time in testing the new suzuki 70hp on my in laws webster 4.6... let just say the performance was very bad... was hitting 4800rpm/20knots in 10knot wind
dosent have permatrim on it yet, dont think i will put one on has it dosent seem to be the problem, before it get to plane, water over fill the transom and mounting bracket before going into plane

anyone know where i can get some in brissy? or recommend a place for installing as well?

[Chimo]

mitc69

Maybe with the 4 stroke weight he needs some pods to better support the bum plus it lengthens the hull at the same time. Common in the states in fact they sometimes build them as part of the hull.

Cheers
Chimo

like these http://www.boatdesign.net/forums/boat-design/extension-planing-boat-33936-2.html

I have done a tinny and they work well. pics are on AF elsewhere.

[mitc69]

yeh i thought about that but dont think a pod ever go with cats. after spending afew hrs on it, it just came to my attention.. that the motor is short shaft, i just replaced the old motor, so i didnt consider the long shaft, but i try the trim tab first before trying to exchange it for long shaft

[hino310]

OMG who set it up. You need to prop it correctly before anything else. If it isn't pulling close to 6000 with two up you are wasting your time adding tabs,foils,pods etc.

[Noelm]

Doubt it's a short shaft! I think we might need a picture from side on.

[Noelm]

manage to get time in testing the new suzuki 70hp on my in laws webster 4.6... let just say the performance was very bad... was hitting 4800rpm/20knots in 10knot wind
dosent have permatrim on it yet, dont think i will put one on has it dosent seem to be the problem, before it get to plane, water over fill the transom and mounting bracket before going into plane

anyone know where i can get some in brissy? or recommend a place for installing as well?
Don't know exactly what you want to get and have installed

[mitc69]

http://s1.postimg.org/kffk0b5xb/IMG_0112.jpg
so where reds are where i plan to put the trim tab on it

http://s1.postimg.org/3vhve2gn3/IMG_0113.jpg
im pretty sure it short shaft or normal some may call it, it got a standed 13 inch i think it on it, havent got around to 15/20 inch yet

[mitc69]

https://www.youtube.com/watch?v=ZP-prkDDB6k&feature=youtu.be

the idea of the trim tab is to prevent that, hopefully it'll lock the water away from building up onto mounting bracket before taking off
i got install at townsville marine while i was visiting the in laws, but end up taking it home to adjust and play with it before return it

[Darren Mc]

Looking at those pictures, it doesn't look like it needs a long shaft.

[Darren Mc]

Looks like it could possibly need lifting a little to me. I don't know about multi hulls but with mono hulls lifting the outboard helps to plane a bit quicker and gets the nose down a bit too.

[Darren Mc]

Oh and definately get the prop sorted. If 4800rpm was max rpm the pitch is definately to high.

[mitc69]

gonna borrow a 15inch off a mate later this wk, rather buying one with no effect lol, i've tried moving engine up, it made it worst=/

[robothefisho]

Hi Mitch,

Setting these single engine cats up can be a bit of an art. In saying that you can get them to work with either alloy or stainless steel props, however unless running the motor very deep (which will throw up huge amounts of water) the prop WILL need ALOT of extra cupping added by a prop shop. The reason is the water depth in the tunnel varies greatly while running and the prop needs to be able to run happily while surfacing and in aerated water.

Getting the motor to its highest rated rpm is the first step as others have said.

[swof63]

gonna borrow a 15inch off a mate later this wk, rather buying one with no effect lol, i've tried moving engine up, it made it worst=/

Going to 15 from 13 is the wrong way for you. It will drop the revs further you need to go "shorter" if your problem is prop gearing. Not convinced it's not something else though, 4800rpm is definitely way under proper wot revs but your speed is also woeful. Changing props to give you 20 or 22kts at 6000 doesn't sound like a win to me, and with suzi's 2.6 gear ratio 13 inch is already pretty short for that motor. Wonder if there are fuel flow or other power-related problems impacting you.

Cheers

[Darren Mc]

There you go. I did say i didn't know about cat's. Thanks for educating me a little. Cheers.

[Darren Mc]

Would trying a four blade prop help? They provide a lot more grip on the water.

[robothefisho]

Would trying a four blade prop help? They provide a lot more grip on the water.

Yes it will. But will still require some additional cupping.

[gofishin]

Are you saying you think it has gone from a short shaft to a long shaft? Or the other way round? Bit hard to follow. What did the dealer say about the new vs old motor height when purchasing ?

... the performance was very bad... was hitting 4800rpm/20knots in 10knot wind ...
Was the 4800 at WOT, i.e. flat stick? If so, and you do have a 13" on it at present, forget the 15" - complete waste of time. Find/read the numbers on the existing prop first. Might have to take it off to find the numbers.

Where was the motor trimmed at this point?

Did the dealer who fitted the motor test it?

Forget tabs, foils and whatever for the time being, sort/confirm the prop and height/shaft lengths first.
Cheers

[mitc69]

i've been reading up websters, they all recommend long shaft, wasnt sure if the one i got installed was one
motor trimmed is middle according to the gauge
they said they tested it, but i always like to get a personally testing

5knots @ 2200 in trolling mode
20knots @ 4800 in 10k knot wind that was plane
27knots @ 6000 in 10k knot wind that was WOT

what im worried about is how the water flood the mounting bracket of the outboard or pretty much where cover seals is, as seen in the video... before it takes off... i know that not normal... trying to fix that problem =/
but wind been so bad cant do anything until it clams down hopefully this wk or so

[Crocodile]

Hello Mitc69,

I have a Webster 4.3 and your photos look very familiar to me.
Straight up the motor is too low.
Your cavitation plate is below the splitter that diverts the water away from the leg.
You have a long shaft motor, that is 20 inches a short shaft is 15 inches which is far too short and I doubt that 70hp Suzukis come in a short shaft.
112086
Measure the height as per the vertical red stripe, it will be 20 inches or about 500mm.
If you lift the motor to the top hole it will be a lot less affected by the water.
I am talking from experience here, my motor sits in the top hole and operates perfectly.
The performance that you show is about right, I have a 60hp two stroke and I get 18 knots at 4000rpm, flat out 27 knots at 5500rpm, by GPS.
I watched your video and I don't see a problem, that wash is normal.
No need for custom cupped propellors ask any Webster owner, the engine setup is no more difficult than any other boat.
This talk about aerated water etc. in the tunnel is incorrect, mine operates perfectly with slippage or aeration, except when she jumps out of the water!

I would be having a good chat with dealer concerning the setup.

[Crocodile]

Ooops,
Should have said without slippage or aeration.

The four stroke may be heavier than the previous motor and the small cats a sensitive to weight on the transom.
Before you fit a foil, check that it does not void the warranty, Yamaha will void if you fit a foil, I don't know what the Suzuki policy is.
I have transom wedges that offer the same result as a foil without warranty issues.
I know because I have used two Yamahas, one with a foil and one with wedges and they both provide the same low-speed planning and trimming performance.

Keep us informed how you get on.

[Crocodile]

Hello mitc69,

I have just checked the Suzuki website and the 70's only come in 20' and 25' versions, no short shaft.
At 155kgs it is a very heavy motor for a 70hp, you may well need a foil or transom wedges or carry extra beer under the foredeck.
http://suzukimarine.com.au/outboards/midrange/product/df70a

[mitc69]

hey croc
is the 4.3 webster fuel tank in the back too? im planing to move the fuel tank to the near font?

yeh gonna give it more testing when wind clam down, sadly cant talk to the dealer there in townsville =/

[PB]

Mate, Dont move the tank, The motor is to low, It needs to come up atleast a hole maybe 2. once you have done this then play with the props. seen pleantly of these boats fitted with 70hp Yamaha 4 strokes.

[mitc69]

yup gonna taken into suzuki cleveland tomorrow and move it up 2 holes and see how it go

[Crocodile]

Hello Mitc69,
any progress?

[Lovey80]

Mitch once you have the height set right I would be adding a foil (or even before). The fuel tank in the rear like that is making the boat ass heavy and ay 155kg the engine is also adding to it. I went through the same process after I fitted a 65L fuel tank to the rear of my 4.3m CC. It launches onto the plane very fast now. Once that is done you can find the right prop though the one you have looks good pre foil.

If the boat is going to be used in the open ocean a lot trim tabs would be beneficial for sure.