Valiant 490 Best prop?

Vega252 · 19 November 2018, 19:01

Hi, Just had a great day on the Clyde with the usual weather.

The rib is fitted with a Mariner 60 2 stroke, with an aluminium 3 blade 11*14 prop.

Boat responds exceptionally well off the mark, but going from mid to high revs it literally leaps forward even in rough conditions as though a turbo has come in.

3 X 20l fuel in the bow has helped the handling, along with a Doel Fin which gets it on the plane much quicker.

Top speed unladen on a calm sea is about 32k at 5500rpm.

Just wondering if a slightly higher pitch prop might calm it down a bit??

Any advice or previous experience with this set up would be greatly appreciated.

Cheers

Chris

Roflhat · 19 November 2018, 19:28

Sounds like you can go up in pitch, will give you lower rpm for the same speed so should save fuel too

spartacus · 04 December 2018, 13:54

Surprised the engine isn't over-revving with a 14 pitch propeller. The lower pitch is perfect for hole shot but going up in pitch should increase overall speed. From memory increasing pitch size reduces 200rpm each time.

I've got a Ribcraft 4.8m with Tohatsu 60hp tweaked to 70hp, that is paired up with a Solas stainless steel 17 pitch propeller at just over 5,200 revs on WOT. I've also got a standard 15 pitch aluminium propeller which is fine for day to day use.

Vega252 · 04 December 2018, 14:01

Thanks for that info. Just got a 17" stainless from Mich Wheel. It was on offer for black Friday so I got a good deal. It's a Christmas present from the wife, so next month before I can try it. I'll come back with results.

Cheers

Chris

Vega252 · 18 December 2018, 18:44

Correction to above (couldn't see the edit button) it's 15" prop not 17.

Vega252 · 08 January 2019, 14:20

Update: Back on the Clyde last Friday, (usual weather).

Prop absolutely brillant. Extra 4 knots.

Improved mid range performance and fuel economy. (1.4miles/litre).

Hoping to get to Ribfest this May!

Xk59D · 08 January 2019, 14:49

What RPM you spinning?

You want to be close to the max higher number with normal load.

Vega252 · 08 January 2019, 14:59

Was at 5400 with the 14" prop, dropped to 5200 with the 15" stainless

(think it's 10,1/4*15). Increase in speed and better fuel consumption.

Must have been really underpropped wi the 11*14.

Weight in the front and doel fin helped as well as it used to "rear up" before getting on the plane.