prop size for Volvo Penta leg 175 hp v6 chev

[odes20]

Hi Can anyone advis us about the following. My mate Quentin has just put a chevy v6 (approx 170 hp) in his 18 ft Sportsman Craft? and it has a Volvo Penta 270T leg. He ran it with a 14x17P Volvo prop and it was revving out to over 5000rpm and only 35 kms per hr. Obviously the prop is wrong. I suggested he needs to to go up in diameter as well as pitch.

I think he should be achieving 65-70 kms per hr WOT
Any ideas what size?

Help really appeciated

Cheers
John

[bakes]

Ive got a v6 chev in mine also. its 210hp on a slightly bigger boat. Its turning a 16 pitch prop and im achieving 33-34knots at 5000rpm

[Spaniard_King]

Possibly the hub has spun... at 5000rpm and a 17...dosnt add up to 35klm/hr

[STUIE63]

Possibly the hub has spun... at 5000rpm and a 17...dosnt add up to 35klm/hr

Garry that is what I was thinking .
mark the prop and the bush and take it for a run then check if the marks still line up
Stuie

[odes20]

Brand new prop! I think the gearboz ratio is 2.15 to 1

[STUIE63]

John work it out here if those figures are correct then there is a huge amount of slip http://www.rbbi.com/folders/prop/propcalc.htm
10% slip should be giving you 34 mph not kph
Stuie