Prop 101 ???

[Noswes]

I have a 2004 Mobius XLV GG with about 2,500 lbs. of ballast. I am running the standard OJ prop (14x18) and am not happy with it. The wake is peaky, unstable, and washy...well anyway I have done the math calculations on the hull displacement and weight and came to the conclusion that I should run a OJ-PART #436 - 13.7 X 15 LC 1 1/8" 4-BLADE .110 CUP unit. Was just wondering if anyone else is running a similar prop and/or pitch/size comparable to my boat. Another persons advice means more than numbers

[Tower_boy]

Good math.. but why do you think this will improve your wake???

It will get you out of the hole and give you a top speed of about 25mph.

I'd adjust the weighting before anything else. everything you say suggests way too much weight in the back. Move some weight forward - remember to try and sink the whole boat.. not just the back. if it planes aft heavy then the wake will be steep but washy and weak. move it forward for the firmer, rampier wake you need.

my 2 cents...

Mike

[Noswes]

Well I have about 1,200 lbs. in the front of the boat. From my understanding of props, the cup has alot to do with aft wash, rather the shape of the wake behind the boat. My top end speed is currently 32 mph, and I usually cruise around 26 mph. I dont think that a top speed of 25 mph would really hurt me. My math supports that I would have a top speed of 28 mph with ballast empty. What size/pitch are you running?

[Tower_boy]

Not to say its not right but I have never come across prop blade shapes affecting wake sizes... I really can't see this fixing a washy wake.

The only problem with 'down-propping' is that you will see a massively inflated fuel consumption - are you struggling to get on plane currently?

As for my prop size.... I am in sports boats now (so this won't help you!), the last boat I had, a 2005 Super Air ran the stock prop.. Never had any need to change it... I always run my sports boats on high five props though.

[Noswes]

Just talked to Bobby, Skier's Choice R & D guy, he said that I should run a 13.7 x 15 but with a smaller cup. He said that they get better gas milage from a 13 x 15.5 than with a 14 x 18 with the heavier weighted boats. Thus you have more torque to the water enabling the boat to plan easier and faster which uses less gas. Stop and go is where you use the most gas. I will loss top end and top end gas milage, but with a 6,000 lbs. boat I will see dramatic gain on the positive side in gas consumption when boarding and surfing.

[Tower_boy]

The original 18" pitch prop may well not be performing that great with lots of weight, equally the new 13" diameter x15" pitch will perform much better - but better gas... Hmm we'll leave that to your testing; I guess alot comes down to how much your riders fall.

In terms of your original problem - the wake; did he mention any improvements? I'd be interested to see if you do... I've never heard of it but thats not to say it isn't possible.