Altitude changes- is it worth changing impeller

[Steelman503]

We live in northern utah. Just got a scarab 165 Id with the 1630 ace 300hp. We will run the boat in northern utah/ we have a house boat in lake powell during the summer but the boat will be ran in Havasu after lake powell challenge in September until dcb poker run in April. Is it worth changing impellers in the summer for our altitude? We have 7 hours and the most we have seen in northern ut is 7200 rpm

 

[gRobi]

Wait for the end of the breaking period (10h), before judging the performance

 

[FSH 210 Sport]

We live in northern utah. Just got a scarab 165 Id with the 1630 ace 300hp. We will run the boat in northern utah/ we have a house boat in lake powell during the summer but the boat will be ran in Havasu after lake powell challenge in September until dcb poker run in April. Is it worth changing impellers in the summer for our altitude? We have 7 hours and the most we have seen in northern ut is 7200 rpm

To answer your question is it worth changing impellers in the summer for high altitude? absolutely yes. The performance gains can be large.

It would be helpful to know;
-the location and altitude of where you boat in northern Utah.

While Bullfrog at Lake Powell is 3960’ ( todays density altitude is 7521‘ & 20% hp loss) Lake Havasu is 450’ (todays density altitude is 4200’ & 12% hp loss) and depending on the altitude / density altitude in northern Utah that could be quite a spread to come up with a compromise impeller, to not be over propped in northern Utah and not be too under propped at Havasu in the winter, but I take it from the tone of your inquiry you’d be willing to change impellers if need be.

SC engines are not as affected by altitude loss as normally aspirated engines are, but those are some extreme conditions. It really comes down to the fact that the engine is not making rated rpm at wide open throttle which is 7950 according to the test done by boating magazine 2023 Scarab 165 ID. Just guessing I’d say you are missing 7-8 mph on the top end.



If it’s only turning 7200 rpm and rated rpm is 7950 rpm the engine driven SC is probably not making full boost pressure and therefore not full HP and definitely not full speed. I agree with @gRobi, see what those performance numbers look like in another three hours. But I doubt you will be at full performance numbers so might as well give Glen a call at Impros or Leading Edge Impellers to see what they can do for you.

 

[Steelman503]

To answer your question is it worth changing impellers in the summer for high altitude? absolutely yes. The performance gains can be large.

It would be helpful to know;
-the location and altitude of where you boat in northern Utah.

While Bullfrog at Lake Powell is 3960’ ( todays density altitude is 7521‘ & 20% hp loss) Lake Havasu is 450’ (todays density altitude is 4200’ & 12% hp loss) and depending on the altitude / density altitude in northern Utah that could be quite a spread to come up with a compromise impeller, to not be over propped in northern Utah and not be too under propped at Havasu in the winter, but I take it from the tone of your inquiry you’d be willing to change impellers if need be.

SC engines are not as affected by altitude loss as normally aspirated engines are, but those are some extreme conditions. It really comes down to the fact that the engine is not making rated rpm at wide open throttle which is 7950 according to the test done by boating magazine 2023 Scarab 165 ID. Just guessing I’d say you are missing 7-8 mph on the top end.

View attachment 205143

If it’s only turning 7200 rpm and rated rpm is 7950 rpm the engine driven SC is probably not making full boost pressure and therefore not full HP and definitely not full speed. I agree with @gRobi, see what those performance numbers look like in another three hours. But I doubt you will be at full performance numbers so might as well give Glen a call at Impros or Leading Edge Impellers to see what they can do for you.

Thank you! I’m currently on the lake and my aviation watch is showing a DA of 6200. The manual shows 3 hours for break in but my brother in law is a ski-doo/ can-am dealer and he said all the high horsepower brp products unlock themselves at completely different times.