proper prop for aq290a and 290 outdrive ?

[LEROYDOZOIS]

theres a random shiny stainless prop on out boat right now, we never really messed with it but dad and i have been curious if the prop is the correct pitch...

ive been told the 290 motors can handle a bigger prop/one with more pitch.. we typically wont push the motor past 4K and usually run it at 3.

is there a chart in reference to what the best top speed will be with a certain propeller ?.

the boat is a 85 26' day cruiser with a 84 motor incase that makes any difference,dry wt says ~3800lbs

 

[Maclin]

Re: proper prop for aq290a and 290 outdrive ?

The best prop is one that lets the engine rev at WOT well into the engine's top rpm range as specified by the engine's manufacturer.
Having typed all that in, read the stickies at the top of this forum to see what all info is needed in order to get a prop recommendation.

In general...:

Drive ratio
Engine's top rpm range
RPM the engine can reach now at WOT with normal load
MPH at WOT

The more accurate these numbers the better prop recommendations will be.

Assuming the engine is in a good state of tune and the drive ratio is correct, then IN SUMMARY...:

• If the engine cannnot reach the top RPM range then it is over-propped, meaning too much pitch in the prop.
• If it can rev past the top RPM range then it is underpropped, maening not enough pitch in the prop.

 

[Maclin]

Re: proper prop for aq290a and 290 outdrive ?

Regarding what MPH should be attainable for any given pitch, here is a Volvo Penta prop guide that covers your setup, just don't ask me to interpret it


View attachment Volvo_Prop_guide_2005_2006.pdf