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Old 03 June 2013, 16:23   #21
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Quote:
Originally Posted by whisper View Post
Don't sit on the fence Peter
You know me ...'are we still here ?' ' Can we go yet?' 'I want to go boating not faffing' etc etc.

He knows he needs to upgrade the SIB..he's just in denial.....

I don't sit on fences ...but then some us haven't had Biff take them out for us....see you Sat morn at LOS CG station
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Old 03 June 2013, 17:11   #22
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To get across whispers well made points:

Loose some weight tubbs, get a decent sib, stop faffing with a long a shaft and get decent engine. Clear? Good....
Oi Peter 5 chins! Pot kettle indeed

I bought the engine to use as an aux primary purpose, I then decided to get a mini SIB as a mess about. That SIB will fit on the RC when I take it down to Cornwall or somewhere other than the Solent where I need to anchor off and the little SIB can get me to and from the shore.

It planes perfectly well with just me.

I do not need 3+ boats like some nobbers
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Old 03 June 2013, 18:20   #23
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You are not a true rib nobber until you have enough ribs of all different shapes and sizes so you can pile them up and make a big rubber pyramid
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Old 04 June 2013, 03:28   #24
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I've got a Zodiac 2.85m SIB (solid floor, air keel) with a Tohatsu 9.8 short shaft on it.

The boat will plane easily with two of us on board, achieving over 20mph very quickly.
With just me on board it goes like a rocket, getting "on the plane" straightaway if you open the throttle (no delay "getting out of the hole")
It's fitted with the standard prop which is the second largest pitch available in the list. (I think it is 8.5)
I think your problem may be that your engine is a long shaft version. Even with a short shaft I found the engine performed better when I raised it an inch on the transom with a block of wood.
I bought the larger pitch prop which I think is a 9.5 and with that fitted it still performs pretty much as above, except there is a bit of a delay to plane with two persons on board. I also bought a TinyTach to see what was going on but have not tested it yet.
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Old 07 July 2013, 12:45   #25
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An update I have had the SIB out on the water at WOT and with the standard prop it is doing 5500rpm.
This is the short shaft version of the Tohatsu 9.8 two stroke engine. At this RPM it will just hit 20mph with one person on board.
It's much happier throttled back a bit, to 4800rpm, where it achieves 16-17mph.

With two of us on board it's similar tbh maybe down 1mph but I did not try it at WOT two up as there were some waves and my wife said she "felt sick and could we slow down"

According to the handbook the long shaft is supplied with a 7.5 pitch prop and the short shaft comes with an 8.5
I guess this is because they assume the long shaft version will be used on a larger boat.
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Old 07 July 2013, 13:55   #26
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I now have a ss. Tested it last week with Tach and took off the 8.5 as it wasn't hitting top end WOT revs went for the 7.5 and is reaching 5700 rpm. Have raised by an inch on the transom. Today with two of us me and PeterM we topped out at 17 knts. Happy days!
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Old 07 July 2013, 14:03   #27
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Sorry heat stroke is kicking in I meant 15.7 SOG, I knew there was a 7 in there!
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Old 07 July 2013, 15:23   #28
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That's great, exactly what we are getting with ours, two up at 5500 rpm about 19mph so l think you have nailed it there.

(Just been out again now my wife recovered, and the sea has gone calm)
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Old 07 July 2013, 15:28   #29
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Must admit took a bit of playing around and I have trimmed out to reduce the splashback its amazing the difference one hole back makes.

Pretty happy with the performance.

Cheers for your post always helpful to compare set ups.
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Old 08 July 2013, 15:57   #30
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If trim hole is set to achieve a paralell boat to water level while on plane including splash out/over transom issues. It's not a trim issue, it's engine sitting on transom at not opt height. Tohatsu engines needs a height optimization compared to most other brands that probably doesn't, it's a lower tail design issue...

Happy Boating
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