Thread: RPM's down...nozzle ring ?
07-18-2010, 07:44 PM #1
RPM's down...nozzle ring ?
Early in the year after my full stage 1 and thru hull was on I was turning 8000ish. I was fine with that, but that is when it was 60-low 70's outside. We are now in the high 80-90's. And pretty humid lately. Today I was turning 7800, with 84 water, 89 air and high humidity. I figure my low RPM's are due to the weather. That is how it is in Michigan every year...I don't want to be prop swapping all the time though. Will the Riva nozzle with rings adjust my RPM's enough for me? What size rings should I get? Bigger the ring the higher the RPM right?
07-18-2010, 07:49 PM #2
The engine electronics pull the RPM down in warm weather to protect it, so a bigger ring may not help too much under load/speed.
Many things cause it to do this, one of them is air density, which is less at warmer temps.
Everyone else will have the same infection in the area, so its an equal field!!
07-18-2010, 09:07 PM #3
07-18-2010, 09:17 PM #4
So I could bump up my RPM's 200 with different rings? What is the drawback? Bigger ring = higher RPM? Or is it the other way around?
07-18-2010, 09:25 PM #5
I read on here that STSPERFORMANCE can machine the stock nozzle to accept the Riva rings. Anyone had it done by him? Come out okay? Cost?
07-21-2010, 10:14 PM #6
Bigger nozzle, higher RPM's? Or other way around? I read 50-100 per ring size, so I assume I need at least two away from the stock 83.
Anyone had theirs machined by STSPERFORMANCE? Or anyone interested in a stock RXP nozzle
07-22-2010, 12:08 AM #7
- Join Date
- Apr 2008
- Plainfield, IL
Id also be interested in getting the stock nozzle bored to accept the rings. Let us know.
07-22-2010, 08:38 AM #8
On a regular RXP the bigger than 83mm nozzle ring doesn't work as well as it does on the RXPX. I was running 7800 RPMs w/ 83mm nozzle 90+ weather, so I put an 85MM in and was running the same RPM with less speed, it felt like (to me) the smaller pump inlet (RXP) was not supplying enough water for the big exit diameter unlike my PX which responds well to the larger rings. I actually ran slightly higher RPMs with the 83mm nozzle.......I am running a very steep pitched 4 blade which might come into play...I'm going to open loop to help my RPM problem because our water temp this time of year is like bath water
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