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Old 25 May 2004, 19:27   #11
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Country: UK - Scotland
Town: Oban
Boat name: RIB Tickle
Make: Humber Assault
Length: 5.3m
Engine: Yamaha 60ETO,Tohatsu 3.5
Join Date: Dec 2003
Posts: 371
I would like a look at the fiches to see just what parts are different and if it is practicable from stripping an old 70B powerhead, I am sure I can pick one of them up fairly cheaply. All the ancilarries are the same including oil pumps etc. The only differences are the carb jets, timing and maybe some porting although I would like to see the part numbers to confirm this. Ideally I want a new 70hp but it will need to wait till I have the cash, not anytime soon
The Yam 60 and 70 weigh exactly the same so 10hp gain is all gain. I am trying to get a bit more speed out of my existing lump, tried a SS prop (try again when it is comes back repitched) and am considering a Doel fin.
Do these really work? My boat is particularly bow heavy due to the long rear tube overhang and all the weight I carry up front. If anything I want to raise the bow rather than the stern but my understanding is that Doelfins raise the stern?
Is the added resistance of the fin better or worse for speed and economy?
I am planning a few long trips this year and a few extra knots would be handy to cut the long journey times down.
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Old 26 May 2004, 17:59   #12
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Country: UK - England
Town: Southampton
Boat name: SMH Rib / War Shot
Make: Ribtec / Scorpion
Length: 4m +
Engine: 10hp Yam / 150hp opt
Join Date: Sep 2003
Posts: 1,894
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Quote:
Originally Posted by Rupert Bear
My boat isn't particularly bow heavy due to the long rear tube overhang and all the weight I carry up front. If anything I want to raise the bow rather than the stern
Have you tried moving some weight further aft?
For best effeciency as speed rises LCG needs to move aft.

Duncan
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