Yamaha F70 Performance at Altitude

[Balky]

Hi All


I have a brand new F70 on the back of my Cski 444 [13 pitch props]. Goes like a rocket at the coast but absolutely DIES at Sterkfontein. Will not even get to plane.


My old motor were Honda 4 strokes [twin 20 HP] never had a problem planing at Sterkies but underpowered when compared to my single F70.


I know of at least 2 other people having problems with these F70s where they cannot get to plane. I also saw a thread back in 2015 by "Fishaholic" from Vereeneging who had the same problem as I with a 17' Yeld. There was not resolution on the forum.


Can anyone help me with advice or the contact details of "Fishaholic" I'd love to know what the solution is. The 11 pitch props are expensive if there is an alternative approach

[Searaider]

I had 2Yamaha 50 4 strokes on my duck and at sea level I could get the boat on a plane on only 1 engine and at the the dams here in Gauteng no chance
The boat had very big props on(I dont remember the size)


Get props that run at about 5000 RPM at an acceptible speed ,maybe 50 kmph