Vensura prop - educate me on bow lift

[crqflier]

I'm in the process of buying a Chaparral 220 SSi, 5.7 Gi VP/SX. It currently has a 19P 4 blade Vensura prop. It's my first boat.

When I did the sea trial, I immediately felt like the boat had a bunch of bow rise out of the hole AND while on plane. Messed around with the trim at various speeds - didn't really settle the bow much (3 adults in the boat including 1 in the bow).

After the trial, did some research on this model Chap and found that other owners also felt the bow rise and plane speed were excessive so they installed smart tabs and solved both issues. They really like the smart tabs.

So then I start to do some reading on Mercury's site, other forums and iboats. I learn that the Vensura is known as an offshore, salt water, outboard, holeshot and bow lift prop. hmmm.

The questions:

• Is bow lift considered a positive thing to reduce the amount of hull in the water while planing (perhaps to reduce friction) or?
• Why would a prop be considered an "offshore" prop?
• What happens if I add smart tabs? Will they be "fighting" the design of the Vensure prop - the bow lift aspect?

Thanks for any comments.

 

[rallyart]

Re: Vensura prop - educate me on bow lift

I put a Vensura on my old I/O and got very positive results. I tried the High-5 and a couple others but it was definitely the best for my application. I can recommend it as being an effective prop that allows you to tune the initial prop slip to give you the starts you want. Holeshot is good because it has a large surface area when you look at it from the back to give you lots of 'push' on starts. It does not cavitate easily. It won't affect the bow rise except that it might accelerate more quickly and you spend less time coming out of the hole on starts. Being stainless steel makes it good in salt water.

Your best bet to fix bow rise is to put more lift on the stern. That's a pretty nice boat and my recommendation would be to put on helm adjustable trim tabs. Bennett make good ones but there are other brands. Smart Tabs are fine but you miss many of the benefits of adjustable tabs. A foil on the outdrive can also help but is not necessary if you've put on trim tabs. The 'bow lift' prop and trim tabs will not work against each other.

Reducing the wetted area of the hull at higher speeds reduces drag. This is usually accomplished by setting the trim rather than any other means. A combination of hull design and trim setting lift as much of the boat out as can be done while keeping it stable. Adjustable tabs can help that some. The Vensura prop on it is not what is keeping the bow up when planing or when you start. It's a design characteristic but adjustable trim tabs will give you more control.

 

[crqflier]

Re: Vensura prop - educate me on bow lift

thanks for the comments. since the boat is new to me I likely won't do anything in the immediate future relative to tabs unless i really hate the bow rise. anyone have thoughts on why mercury would call this an "offshore" and "outboard" prop? are there characteristics to props that would lend themselves to those applications?