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Old 31 August 2010, 10:02   #11
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Could it?
well you got me thinking there, if your running against the flow your working it harder, if your running with the tide theoretically less effort reqd, which means if you have WOT ..........
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Old 31 August 2010, 10:04   #12
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Or, keep an eye on the tacho and throttle back when it approaches 6k
of course but in this case the thottle is nailed open and past the 6k marker!! naughty boy!!!
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Old 31 August 2010, 11:35   #13
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Cheers Matt. What about guaging the adjustment of the stop screw - is it done how I said, ie on the water - run, adjust, check etc? Or does one turn = 250 eg?
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Old 31 August 2010, 11:39   #14
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well you got me thinking there, if your running against the flow your working it harder, if your running with the tide theoretically less effort reqd, which means if you have WOT ..........

Perhaps a strong following wind would cause it, but tide, .......
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Old 31 August 2010, 11:40   #15
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i would do adjustments on the water as very easy to do. your working rpm should be 5750-6000, if the engine is pulling anywhere in between then all good!!!
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Old 31 August 2010, 14:12   #16
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i would do adjustments on the water as very easy to do. your working rpm should be 5750-6000, if the engine is pulling anywhere in between then all good!!!
Takeing advice from MATT H about er,.. LOWERING revs!!!??? Like asking George Best how to cut back on the BOOZE!....
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Old 03 September 2010, 03:40   #17
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Chaps - another thought -changed over the prop last night to the 14 so I can try that but while there I noticed the engine height. According to the Merc' manual and conventional thinking on threads I searched on here it should have the cav plate level or within a inch below the hull bottom:



Mine is an inch above, see pic below (engine fully trimmed in) - would this lead to more likely cavitation on sharp turns and hence more likely to over-rev as noted? I am sure I had it trimmed well in when turning. The mounting holes are 3/4 inch apart so should it be dropped 2 holes?

And any thoughts on a 12 pitch vs 13 pitch on this sort of SR/60hp set-up? As long as it does 30 knts or so I'm more concerned with pull for a mono skiier than top whack.

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Old 03 September 2010, 05:00   #18
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I run my SR4.7 with the cav plate an inch above the keel line, with no problems.

The lower unit has a 12:22 (1:1.833) ratio, so I reckon a 13" pitch would be right for general running about with 2-3 persons on board (mine has a 12:28 or 2.33:1 ratio and I use a 17" pitch with a Twatsoo 60). A 13" pitch prop should give you 30-35 kts, depending on sea conditions and load. If you intend pulling a skier with 2-3 people on board, you may need to drop to a 12" pitch, but as you already have an 11" pitch, try skiing with that first, before you spend a fortune on props you don't need.
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Old 03 September 2010, 12:29   #19
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Thanks for that - the 11t was definitely too low I think but I've got my eye on a 13 so will try that. Probably have the 11 and 14 to sell so that should balance out the £'s maybe a 12 and 13 for ski/cruise will be a good pair.
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