Propellor size

[Big Ears]

Hi Y'all,<br /><br />I am considering changing my prop size from a 17" to a 19" as I am not pulling skiers and the advice I have been given is thatm I will get more topend speed and reduced fuel consumption for cruising. If anyone can clarify this for me I would really apprecate it,<br /><br />all the best from downunder<br /><br /><br />Luke

 

[Jdeagro]

Re: Propellor size

Luke;<br /><br />First thing everyone will tell you is to check the manufacturers recomended RPM rnage at Wide Open Throttle and make sure your prop is in the range. If for example the manufacturers Specs say between 5400 RPMs and 5800 RPMs, and you ar at 5800 then you can increase the pitch. This will drop your WOT rpms down a bit to say 5600 RPMs. However if you are already at 5400 you do not want to go lower because at cruising speeds you will likely be below the best torque curve.<br /><br />Your acceleration to plane will suffer and probably more than you think. <br /><br />If you are looking for the best efficiency, there is no substitute for Smart Tabs, but make sure the RPMs at WOT are correct.

 

[Big Ears]

Re: Propellor size

Many thanks John,<br />I have a '84 Mariner that is currently being rebuilt and following your advice, I will stay with the 17" until the motor is well and truly run in before looking into the new prop.<br />Once again, thankyou. I really appreciate you taking the time to clarify my question<br /><br />all the best<br /><br />Luke

 

[Big Ears]

Re: Propellor size

Woops, forgot to ask.<br /><br />WHAT are "smart tabs" ?

 

[Dunaruna]

Re: Propellor size

Hi Luke, welcome to i-boats!<br /><br />Smart tabs are a popular brand of tabs on the back of boats (you know, the step looking thingamajig). <br /><br /> http://www.iboats.com/products/16/39283_nauticus_smart_tabs_automatic_trim_tabs.html <br /><br />Whats your hometown?<br /><br />Aldo

 

[Big Ears]

Re: Propellor size

AAAAh, I have a basic version of the same sort of thing fitted to my boat which I can adjust manually if one of them is out of level with its twin.<br />Hometown is Wyoming, just 4 k's north of Gosford.<br /><br />Thanks Aldo

 

[Dunaruna]

Re: Propellor size

The smart tabs are probably the next step up from what you have - but I'll leave that to nautijohn to explain, he is very knowledgable in this field.<br /><br />Aldo