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Coontakinta
13-03-2016, 09:04 PM
I am not satisfied with the performance of my 2014 F70. Its hitting the rev limiter producing 30.1kn @ WOT, trimmed out fully, with my usual tournie set up. That being two anglers n gear and full 70 litre fuel load.
Standard 14"p alloy yamaha blade.
Boat is a 2014 Renegade 460SC. The 70 is its max hp. Well hull is actually rated to 75hp but the 70 is the biggest yam 4 stroke I could put on.
I realise and accept these fiqures are adequate and even acceptable and that i could simply not push the throttle so hard but I want to squeeze out more speed especially when travelling the sometimes glassy water i encounter not to mention the fact that its nice to stay ahead of SOME of the competion.
My question, for those in the know, is at what trim setting should I be recording my speed @ rpm with the view of replacing the orginal blade with a higher pitch S/S one?

aussiebasser
13-03-2016, 09:19 PM
Trial and error with different props is the only way of doing it.

Noelm
14-03-2016, 04:47 AM
If its hitting the rev limiter pretty easy, best guess is the next size prop up would be a start, is the setup new? if so, the dealer will swap props to get it right, as long as the current prop is unmarked.

Coontakinta
14-03-2016, 05:40 AM
Yes have spoken with dealer and together we are working on a satisfactory outcome. I said I would do the leg work if they are prepared to supply me the props for testing. Thing is when recording the information at what level of trim should I be using?
Info so far. X rpm by 1000

61/2rpm 28.1kn
Half trim
No trim 57rpm
25kn
Full trim
30kn @ 63/4rpm

scottar
14-03-2016, 06:54 AM
Bit of info on the Verado Club website http://www.veradoclub.com/index.php?topic=137.0 . As a rough guide an inch of pitch will cause a change of about 200 rpm but as aussiebasser posted you will need to test them to make sure you are happy with the outcome.

gofishin
14-03-2016, 07:00 AM
...Thing is when recording the information at what level of trim should I be using? ...The 'sweet spot', which is where the prop shaft is ~parallel to the water. Here the steering is usually lightest both ways (assuming the steering trim tab is set correctly) and the speed is maximum.

If you trim out from here, speed drops off as revs increase due to the prop starting to ventilate. No point testing speed vs revs at any trim beyond the sweet spot.
Cheers
Brendon

Noelm
14-03-2016, 07:27 AM
There is no "trim level" it varies from boat to boat, once again, it's a trial and error thing

aussiebasser
14-03-2016, 07:36 AM
The correct level of trim is the spot where the GPS is recording the highest speed at WOT, but this is only the correct trim when flat out. she'll want a lot less trim at less speed. You'll need some BOST to work it out because every boat is different.

Chris Tucker
14-03-2016, 07:38 AM
what are you calling "no trim" and "full trim"? I suspect full trim is all the way under and no trim is approximately parallel with the keel.

In 2 of the three cases in your example you aren't on the rev limiter so I suspect you're pretty close to perfect. Maybe go up 1/2 inch in pitch but no more than that.

For the record if you have an engine trim gauge feel free to rip it out or cover it. You should be responding to have the boat is feeling and performing not what the gauge says.