Changing prop for more top speed.

[taymax14]

I have a 21' 1999 Centurion Ski Boat with an inboard 350 Mercuiser V8. Right now it has a 13x13 LH 1 1/8 Prop that is stainless steel. I'm looking at trying to get more top speed. With 5 or 6 people in the boat the top speed is only 30-32 mph (true speed from my GPS. Boat reads more like 35 mph). I would like to get it up to 34-35 for skiing. The RPMs fluctuate a bit, but stay pretty close to 3800. This is at a lake that is higher in the mountains, about 7000' above sea level. So at some other lakes around 5000' it runs around 4000 RPMs. I was thinking of getting a new brass 13x11.5 LH 1 1/8th. Will this make a difference? any other options or things to try? Thanks!

 

[steelespike]

Re: Changing prop for more top speed.

I'm not an expert on your boat
You can re jet the carb for the elevation you run at.Some times they suggest a timing change. Marinas at that elevation probably now how to jet and if any timing changes.Are you sure the motor is well tuned and healthy?Good strong compression?
I would think a 13 X 13 is pretty far down the list.
My old18' Chris Craft(53) ran a 95hp flat head 6 cylinder in a 1500 to 1800 lb boat something like a 12 X 13 prop would turn max rpm3,600 with little drop with 3 adults and 2 kids aboard. about 570lbs.Point is, basic same drive 1 to 1 a 12 X 13 is basically the same prop your running especially if you consider the hp difference.

 

[taymax14]

Re: Changing prop for more top speed.

It's fuel-injected so it shouldn't be a problem there. yeah strong compression and just put new plugs and a fuel filter in it.