Prop Diff

"JCH, I can't answer that

"JCH, I can't answer that one! You really need an OEM manual to refer to for WOT, and then prop accordingly.

You may have two different props for two entirely different types of use.
*Boat loaded heavily, for example.
*Boat not loaded heavily and a long cruise in mind, for another example.
*Towing a skiier or tuber, for another example.

Each prop has a spceific use for the same hull.

If you don't vary your load, then find one prop pitch that works and gives the correct WOT RPM, and make your spare prop identical.

."

"No, a 14x17 would not be equa

"No, a 14x17 would not be equal to a 15x15. Think of "more pitch is for more speed" and "more diameter is for more thrust". A small, comparatively light boat will need a propeller with smaller diameter than a larger, heavier boat, but will benefit from more pitch. A larger boat needs more blade area than a smaller boat to be pushed on the water.

Your boat will go slower with a 15x15 than with a 14x17, but it will stay on the plane at lower speed.

There is no OEM propeller size for a boat. Two identical boats with identical power plants may need different propeller sizes depending on the application. It is a matter of trial and error (and a combination of science and art) to determine the right propeller size for a boat.

Clear as mud?"

I understand! I just been rack

I understand! I just been racking my brain. I have been now starting to pull more tubers and skiers and wanted something to get the boat out of the water faster. i was thinking a 14x15 instead of my 14x17. I was just not understanding what the difference is in blade size and the difference diameter makes. You guys cleared that up for me. Thanks a bunch.

according to Volvo Penta datab

according to Volvo Penta database aq125a max rpm's are 5000. So WOT should be within a couple hundred from that correct??

"Not exactly... If you downloa

"Not exactly... If you download the owner's manual on the website and carefully read page 2, you will see that for the AQ125A a MAX RPM RANGE of 4000 to 4800 RPM is specified. This means that with "normal" load, the correct prop is the one where the engine's WOT RPM falls within that range."

"Thanks Robert, Mine is about

"Thanks Robert, Mine is about 4600-4700 now.Im in the safe zone...lol..my spare prop is a 14x19 and its too much for the engine. I have been getting into skiing and tubing more now so i want a little faster plane times but also try to keep the best top end possible too. Im not sure to go with a 14x15 or a 15x15 for that purpose. Also on volvo pentas website :

http://www.volvo.com/volvopenta/na/en-us/marine_leisure_engines/engines/out_of_p roduction_engines/out_of_production_engines.htm


look on this page!!It states here 5000rpm max, however, your correct on page 2 it states 4000-4800 hhmmmmmmmmm.... "

sorry that link didnt go to th

sorry that link didnt go to the correct page!!

if you fill in that page and get to the 125a page. look on the upper right hand side where it shows the specs. it says 5000rpm??? I guess Volvo doesnt even know lol??? smoke em if you got em HA

"Gents, a correction if I may.

"Gents, a correction if I may. I know by experience that 4000 at WOT is way too low for that engine, so I had a look at the manual and there is a typo. It actually states that the propeller size should be such to achieve 73-80 r/s (which is 4380-4800 RPM) at WOT."

4380-4800. very good El. P tha

4380-4800. very good El. P thanks for getting out that dusty old manual !! Now i need a new tach as mine currently bounces around a lot...trial and error on the props now is what ill do.
I currently have a 14x17 and a 14x19

I gonna buy a 14x15 and a 15x17 for it. Ill have a prop for every occasion!!!. And they're so easy to change out!