Best Prop for Response with 409SS Monsoon

[bewls]

Hi, I have recently bought myself a 2014 Response with 409SS engine upgrade. We mainly use it for skiing and barefooting but seems to be revving high with the standard Acme 515 prop on it. Has anyone got a 449 or 425 prop on their boat? Which one would you recommend to go with the 409SS engine?

Cheers

[Woodski]

@bewls:  what is the RPM:MPH ratio at skiing and barefoot speeds?  With a 1:1 gearbox, you should see pretty close to 1000 rpm per 10 mph.  The techs at Acme will provide some pretty good information on prop details and each step effect of bumping up the pitch.  I recall w/o my notes the 515 > 449 change was ~200 rpm drop, but I would call Acme to confirm.  Also, I would compare your speed control RPM to the tach reading to verify the accuracy of the tach (or both!). 

 

[bewls]

20 hours ago, Woodski said:

@bewls:  what is the RPM:MPH ratio at skiing and barefoot speeds?  With a 1:1 gearbox, you should see pretty close to 1000 rpm per 10 mph.  The techs at Acme will provide some pretty good information on prop details and each step effect of bumping up the pitch.  I recall w/o my notes the 515 > 449 change was ~200 rpm drop, but I would call Acme to confirm.  Also, I would compare your speed control RPM to the tach reading to verify the accuracy of the tach (or both!). 

 

Thanks @Woodski you are correct in that 1000rpm per 10mph but it seems die off over 4000prm. I'm just not sure if it's ideal for a motor to be doing 4600rpm towing a barefooter and if this uses a heap of gas in doing so.  I will call the people at ACME to see what they say.

[ahopkins22LSV]

@Dare2goBare may be able to provide some good insight for you.

[Dare2goBare]

19 hours ago, bewls said:

Thanks @Woodski you are correct in that 1000rpm per 10mph but it seems die off over 4000prm.

Yup.... after 1k it does die off from 1k to 10 mph,  I'm running the 515 and top out 47 mph @  5100 rpm. Thats with a full tank

and a crew of five with gear, at sea level and the same at the lake, 1300 ft.. Now the 409 purrs like kittin when we're footing,  Im at 42 Mph with my footing and have no concerns what so ever. A solid constantly pull up to speed!  but yes she does drink a bit more!

On a side note I forgot to mention, ACME will recommend the 515 for your boat with the 409.

Edited February 1, 2017 by Dare2goBare

[ahopkins22LSV]

To the OP, my concern with changing out the prop to achieve lower RPMS at 40+mph is she is going to be a dog out of the hole for anyone that slaloms. Now, if you and your buddies don't slalom at all that probably isnt a factor. Although I would keep the 515 for when you go to sell it as most interested in the boat will be skiers.

[Steve B.]

I've wondered if folks have experimented with two blade props on our rigs?

Steve B.