High altitude impeller use at low altitudes

[Dirtymunoz]

Hi, so I looked around for awhile and couldn't seem to find a relative answer to this question. I'm gona have my impeller repitched for 4500ft by impros but curious as to using the same impeller at lake Havasu or canyon lake in AZ. Maybe 1 time a year. Will I loose performance at those 2 lakes or will I cause other issues? Call it laziness but swapping the impeller back to stock for 1 time a year has me questioning the pros or cons. Thanks in advance

 

[FSH 210 Sport]

Hi, so I looked around for awhile and couldn't seem to find a relative answer to this question. I'm gona have my impeller repitched for 4500ft by impros but curious as to using the same impeller at lake Havasu or canyon lake in AZ. Maybe 1 time a year. Will I loose performance at those 2 lakes or will I cause other issues? Call it laziness but swapping the impeller back to stock for 1 time a year has me questioning the pros or cons. Thanks in advance

You may loose some top speed at the lower elevation lakes. The pump is going to pump the same amount of water at a given rpm regardless of altitude with a given impeller and it’s associated pitch.

So what you’ve got going on right now is that your engine can’t come up to rated rpm due to the altitude driven horsepower loss, 13.5% without adding in density altitude which could raise your hp loss to as high as 27-30% depending on conditions, and the OEM pitched impeller. The altitude hp loss is a double whammy as your engine can’t speed up enough to achieve peak hp rpm’s due hp loss and too high of a pitch.

You cannot change the altitude but you can lessen the pitch, or increase the mechanical advantage the engine has to get the engine close to rated rpm. So at rated rpm with a repitched impeller your boat will not pump as much water as the oem pitch at the same rated rpm.

It is possible you could have some cavitation if you accelerate really hard from a standstill, as now your engine is closer to sea level and is producing closer to rated hp. However depending on what time of year you are going, the density altitude could be pretty high with high ambient temperatures. Based on other peoples posts on this subject, I’d say you will just have increased performance at Havasu.

Id say the increase in performance at high altitude will be well worth it overall. If it was me and I was going to be at low altitude for a long trip like to the ocean, I’d put the OEM impeller back in for that trip. The impellers don’t take very long to swap, I can do both of mine in less than a hour and a half.

 

[Dirtymunoz]

Awesome thank you for the quick response. Will adding the lucky13 cone help with the cavitation issue if i do come across it ? And the most I see myself using this boat at low altitude is 1 to maybe 2 days a year.

 

[FSH 210 Sport]

Awesome thank you for the quick response. Will adding the lucky13 cone help with the cavitation issue if i do come across it ? And the most I see myself using this boat at low altitude is 1 to maybe 2 days a year.

I have no experience with the L13 cone other than what Ive read here, some folks swear by them and others say there was no difference. I’d say if you have no issues now with cavitation, chances are good you will either have no issues or they will be minimal. If that issue does come up and it is in such proportion that it warrants attention then worry about it. Also, it seems the best fix for cavitation is to seal up the intake tunnel.

 

[JBehrens]

I have an impeller pitched for Lake Powell ~4000ft and have ran it at Lake Mohave. You loose low end torque at lower altitudes due to the impeller having less pitch leading to more cavitation. If it's only one or two times a year at low elevation then you probably won't have an issue, just ease into the throttle to avoid cavitation and know the boat won't get on plane as fast. I did have one day in November that was nice a cold where I hit the rev limiter with the pitched impeller so I guess that could happen too but I have not seen that in the summer.

L13 cone makes a massive difference and I would use one no matter what.