Tohatsu prop needed - Page 2

Salty · 16 August 2012, 09:11

Quote:

Originally Posted by lightning

In the USA though

I'll see if they ship to the UK and how much it costs....when I was buying Ferrari spares (for my old Mondial) from the USA it often cost $100 to ship a fairly small/light package. The cheaper option is a "flat rate box" but it's untracked and too small for a propeller.

Fook me, buy one from the UK then! £200 quid is small change..............

(They do ship to the UK, change the currency to euros and the shipping prices are shown and look pretty reasonable)

Salty · 16 August 2012, 09:15

USPS First Class International Mail - $18.95

Sounds like that Ferarri garage were ripping you off mate !

lightning · 17 August 2012, 20:45

Probably.

I complained about their postage charges and they wouldn't deal with me again after that.
$100 to ship a fairly small and light plastic panel. Plus I had to pay customs and VAT on the whole value including the postage charge.

Amazingly it was STILL cheaper than buying it from the UK.

Fenlander · 17 August 2012, 21:17

>>>contacted Tohatsu and they said that on a 2.8m SIB the 9.8 2-stroke should be fitted with the largest pitch prop that is available.

Why would you want to do that?

lightning · 22 August 2012, 17:40

They said it would give the best performance and higher top speed. Also they said it should help to reduce the cavitation I'm getting with the lower pitch one.

Anyway I've bought the higher pitch prop from Ribshop, it's actually a 9.5 (the one fitted as standard is 8.5) and I will try it out to see what difference it makes.

ribboy · 22 August 2012, 18:33

Try Steel Developments in Wandsworth,great service and great knowledge.

lightning · 22 August 2012, 19:00

Too late now! As I've bought the prop from Tohatsu.

Thanks for the advice though, I will test both props on the water and report back when I've got the results.

lightning · 11 September 2012, 15:09

Not sure what to make of this new propeller, I tested it and the SIB certainly goes well with the 9.5 pitch prop, although it went well with the 8.5 pitch one fitted as standard.

Tohatsu say that on a "light" boat I should fit the 9.5 pitch, they define "light" as in the range 100lb-500lb (45kg-226kg)

Do they mean total weight of the boat including the engine and crew?

Myself and my wife between us weigh 130kg plus the boat about 40kg including extras and the engine 26kg which is about 200kg in total.

Still in the "light" category

ribboy · 11 September 2012, 19:30

Lightning

Have you tried trimming up the lower engine bolts with stainless steel washers this may increase your speed , you need to experiment with this but we found it to work if you need a hand give me a shout.

Ribboy

Locozodiac · 11 September 2012, 21:23

Sorry to spoil the party, but you are missing some important isues here :

1-A 280 sib is relatively small has too much hull drag, worst trying to plane with more passengers. One thing is to push, move sib, other to full plane.

2-It's s not a go for a short, large pitch issue or call the distributer as this test must be done under trial with an induction tach previously installed to check if inside safe working parameters.

3-Buy a Tiny Tach which is spark programable an set it to fire 2 spark per revolution. The rpm working factory parameters for that engine which is only 170 CC is 5000 to 6000. Stay with the prop that will give slight passing 5500 rpm, will have better hole shot than placing a prop that will give near 6 K rpm nullifying hole shot.

4-Assume you have a well inflated sib to 3.5 psi, tubes and keel, well trimed, correct transom/engine seated and passenger ballanced, correct ?

5-If nothing works out as expected including family dissapointing, you need definitely a larger sib in the 360-380 range, will work better if keeping same engine as hull will drag less and sib will slide better.

Post your pitch/rpm findings if going for a tach.

Happy Sibbing

lightning · 11 September 2012, 22:55

The boat actually performs well, l bought the higher pitch prop because l was getting cavitation and after contacting Tohatsu they recommended it.
But l was testing it on the canal, on the open water the boat planes within seconds of opening the throttle, achieving over 15mph easily using either prop....so l might have wasted my money!
I have not yet tried it on full throttle to see how fast it will actually go.
Also raising the engine on the transom using a block of wood has improved the general performance.
So it's now just a case of which prop to leave on, and which to sell. The 8.5 or 9.5 pitch.

Salty · 12 September 2012, 08:29

I'd be interested if you decide to sell the 8.5 as I have just taken a nice chunk out of one of the blades on mine.

lightning · 12 September 2012, 08:46

I will be trying the 8.5 back on today, but will have to be careful as there's a blanket 6 knot speed limit here, so l cannot be testing it for RPM at WOT!

Locozodiac · 12 September 2012, 15:49

Quote:

Originally Posted by lightning

On the open water the boat planes within seconds of opening the throttle using either prop....so l might have wasted my money! I have not yet tried it on full throttle to see how fast it will actually go. So it's now just a case of which prop to leave on, and which to sell. The 8.5 or 9.5 pitch.

When you say planes well with both props, is it with you alone, or with family too ?

You must test if possible on flat calm waters with the load you will be cruising with, full throttle and check if inside factory working parameters (5K-6k) at wot. That's why a induction tach is needed, you could test each prop with you alone and fully family loaded and check both wot readings.

A 9.5 prop will slow down your rpm compared to the ones achieved with the 8.5 delivered factory standard, but as you don't know yet your wot max rpm, you will be doing a wild guess seems at ear sound which could be counterproductive for your engine.

If you already have invested wisely or not on a new prop, buy a Tiny Tach and check, a TT will be usefull to check runing hours for preventive and corrective maintenances as well, same as with a car.

Happy Sibbing

lightning · 15 September 2012, 19:39

So I tested both props and guess what....both have their advantages/disadvantages so there's no definitive answer!
The 8.5 pitch accelerates very fast and gets on the plane instantly with one or two persons on board. The boat will do an easy 18mph on rough water, probably more on the smooth sea.
It will sit at 15mph on about 2/3 throttle.
The 9.5 pitch feels similar with one person on the boat, almost instant planing and easy 15mph cruising speed. RPM seem a little lower but that's only how it seems by ear, as I do not have an RPM meter.
With two people on the boat it gets on the plane with no problems but takes a bit more throttle to do it. Once going it will exceed 20mph, again on fairly rough waters. Acceleration seems a little slower.
So both props are good, depending on what you want. I think I will leave the 8.5 prop on for now.

Locozodiac · 16 September 2012, 00:59

To plane fast and break hull's drag faster go full wot until at plane, once there, reduce throttle to maintain plane. A 8.5 prop will give more rpm that a 9.5.

Happy Sibbing

lightning · 16 September 2012, 13:21

That's what I found.

I will buy an RPM meter as suggested and test it properly when I can get back on a Scottish Loch, probably next year.
Until then it's back to trolling on the canal, or 10mph max on Windermere, where either prop will do.