Nose of sib to high

[Mickhitchuk]

I have been looking in the search items, but not very good searcher so sorry if I missed a previous thread on this
Anyway (boat Yamaha 3.1 sti motor Tohatsu 9.8)
Running in now a 3/4 throttle the nose is up way to high, will this level out at wot or get worse?, the motor is on the first notch and I sit in the middle on a bean bag, the air floor is at the correct pressure
I see zodiac sell some fins to put on the back, but they look like they will get in the way of the transom wheels, or a hydrofoil fitted the the outboard help, or I see some people talk about packing the outboards up
I'm haven't got an anchor yet so would the weight of that help?
Just trying to preempt if I have a problem as I'm off to the boat show next week

[Fenlander]

I wonder if you are running at transition speed from displacement to plane? This speed usually has a very bow up attitude until a full plane is achieved and is an attitude you wold normally pass through as quickly as possible.

[Nick Hearne]

When you say the engine is on the first notch do you mean the one nearest the transom? As the leg is as close to the transom as it can be?
If not move it in closer to the transom,

[Mickhitchuk]

Thxs Nick, yes the leg of the motor is as close to the transom as it could be, fenlander could be right as I only had it a wot for 1 minute

[matt h]

Fenlander is totally right. Its a short sib! Nothing to worry about and first notch is correct

[beerbelly]

just crack it wide open and you should climb over the water and onto the plane then just back off to a comfortable cruising speed

[Mickhitchuk]

Who looking forward to getting it run in

[Mickhitchuk]

Doh I mean whoo hoo

[lightning]

I have a similar setup. Zodiac 2.85 Solid with Tohatsu 9.8

Two up the boat will achieve about 4mph nose down at 2,000rpm. (I have a tacho fitted) after this the nose does start to rise.
This continues until 3,200rpm when the nose is right up and still only 6mph. (with great big wash)

Then an extra 300rpm sees it plane, and then it's off, rapidly accelerating to 15mph+. The bow comes down and the wash reduces greatly.

2,000 rpm is achieved with the throttle just past the "start" position.

I have tried all five trim positions and it ended up in the middle one. However there was a fair bit of splashback at planing speeds. This was completely solved by raising the engine on the transom 2cm with a block of wood.

As a start point the engine leg should be at 90 degrees to the water at trolling speed.

I also tried a higher pitch prop. This reduced the RPM making the boat plane at 2800rpm rather than 3300rpm. The RPM was down from 5500 to 5000 at WOT. Max speed was the same! 19-20mph.

However it took a bit longer to plane where with the standard prop it's instant. So l fit the standard prop for Scotland and the higher pitch one for the canal/broads etc where it's lower revving at 4-6 mph.

[Max...]

Unless you have some weight up front most SIB's are pretty nose up and a bit hairy in a blowy head sea. Definitely get some ballast up there with fuel, gear (incl anchor) or whatever.

[lightning]

True, but the O/P is trying to get his boat to plane. With a Tohatsu 9.8 on my SIB it will plane in any trim position and although my missus sits at the front on the bench seat, it still planes if she sits at the back.
It's just much better if you balance the weight. Fuel tank and wife at the front!
With my 6hp Mariner it was a lot more critical though.

[Max...]

Ahhh, didn't realise it wouldn't actually plane, should do one up for sure with the 9.8 even at 3/4?

[Mickhitchuk]

Thxs for the help all, it's early days for me with this motor, but seems I haven't got too much to worry about, just need some more time out in it

[Fenlander]

So where are you sitting relative to fore/aft, do you have a seat fitted, are you using the 12l Tohatsu fuel tank, is the tank full and where is it, are you alone and do you have any more kit at all?

[Mickhitchuk]

Hi,
No seat fitted, I sit in the middle behind the fuel tank that's strapped onto the official air deck mounting points
I use a short tiller extension
No extra kit as of now as I'm building that up, of course I have a lifebelt
Need to get an anchor and other safety stuff, so looking out for a pelicase

[Mickhitchuk]

And yes I'm on my own with usually a full tank of fuel

[Fenlander]

Oh well it sounds like you are set up OK to plane in a fairly flat attitude. It might be better if next time you use your allowable period of max throttle (per running in instructions) to push over the hump where it will flatten on the plane and you can back off the throttle to 3/4 and still maintain the plane.

[Mickhitchuk]

Hope to give it a blast this weekend, I'll try that and let you know
Thxs

[lightning]

Might be worth re-reading my post about this engine on page one of this thread.

[Mickhitchuk]

Hi lighting. Thxs for your post, I have had a good read of it indeed I have it printed out and ordered a cheap eBay tacho, as when I next go out I can try the various help I have received, so if you see someone around shoreham working through a bunch of paper work that will be me