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Old 28 May 2016, 04:43   #11
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As we changed the prop shortly after buying the boat I don't really know. It must be better as we use less revs at cruising speed and it was just better all around - not very scientific I am afraid. Still uses lots of petrol
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Old 28 May 2016, 07:24   #12
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Quote:
Originally Posted by paintman View Post
How do you find fuel consumption with the 4 blade compared to the 3?
If you have higher speed at the same (cruise) RPM you have less petrol consumption in this range.

Just look at post mentioned above by @"solent spence"
If he mostly uses 3000 RPM range the best petrol consumption he has on two last props
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Old 28 May 2016, 11:00   #13
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Useful replies guys😀

I'm going pay my local boat dealer a visit to see if he has any spare props to try.

I do think I need to go at least a pitch bigger to get the revs down. I'm cruising at over 4000 rpm which seems to high.

The four blade probably won't offer any more speed unless the extra stern lift gets the back out the water to reduce drag. Testing will only tell. A more economical cruising speed is my main priority.
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Old 02 June 2016, 17:21   #14
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Go do some tests using the mercury prop selector, great tool.. Aren't you perhaps cavitating? Is the motor trimmed correctly and at the right transom height?

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Old 18 June 2016, 15:04   #15
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Right. Managed to borrow at prop from a local supplier. It was a 13 1/4 x 19 which is the same diameter but next pitch up from what I got now, which was a result as it's the exact one I thought might work.
However, not great results today. Lowered revs by 300, but also lost top speed which surprised me. Light load it maxed out at 31 mph which was less than I had on the 17 pitch. It's still gave alright performance, but slower getting out the water. Thinking I will stick with what I have got unless any other thoughts?
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Old 18 June 2016, 16:09   #16
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Go back to your original prop.
You had better shot
Did you measure WOT on nominal load ?
You have mentioned in first post that you was a little over WOT (5600 - 100 over)
100 it can be even measure error and please remember that you have be in WOT range at nominal load.

So if you go always with other person and some bags - make test having such load.

Better shot, better high speed - why change prop

>>>>>>>>>>>>>>>>>>>>>

And you were in WOT range I suppose:

Full Throttle RPM Range 5,000-6,000 RPM HONDA BF75
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