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.

 

[Stevenpaganelli]

Did you ever upgrade your impeller I’m in a Scarab 195 HO and it lugs in Utah Lake, barely runs in strawberry, lake Powell it does alright but still sluggish.

 

[FSH 210 Sport]

Did you ever upgrade your impeller I’m in a Scarab 195 HO and it lugs in Utah Lake, barely runs in strawberry, lake Powell it does alright but still sluggish.

@Steelman503 hasn’t been around since July 18 2024.. maybe he will get an email ping from this thread.

I can tell you that going to a repitched impeller for high altitude use will yield dramatic results. There are two impeller places available to you to either A-get a new impeller and have it pitched, or B-Send your impeller off to get re pitched. I recommend buying a new impeller and have it pitched so you will always have an impeller to use.

Before you send your impeller off, or get a new one, you will need to tell each impeller place what rpms you are getting at these lakes. Then you will have to make a compromise / decision about where you boat the most and have the impeller pitched for there. Example, if you boat at Utah lake the most, then you would get the impeller pitched for that lake to run at max rpm, you will still be a bit over propped at Strawberry and a bit under propped at Lake Powell. But! The boat will perform way better at all of those lakes… If you spend a lot of time at say Strawberry, you could get a prop pitched for that lake and be a bit under propped for Utah Lake, then have the other impeller propped for Lake Powell.. Make sense? Hey if you have the dough and don’t mind swapping the impellers you can have impeller(s) for each lake and have the best performance possible at each lake.

Impros-Glen

Impros, LLC - The Impeller Pros

Impros, LLC is your Personal Watercraft (PWC) impeller repair/jet propulsion system and modification service. We are also the premier online distributor of major PWC stainless-steel impeller and other propulsion products.

impros.com

Leading Edge Impellers-Dave

Leading Edge Impellers | PWC - Jet Boat Impellers - Pump Parts - Repair

Leading Edge Impellers

leadingedgeimpellers.com

 

[Stevenpaganelli]

I’ve got your site pulled up to order a new one, and you’ve got me convinced. How much is it to have one installed and do you need to go to a boat dealer? Or is it something easy and safe enough to drop in on your own?

 

[FSH 210 Sport]

I don’t know what’s involved in changing an impeller on a scarab, perhaps @Luc Lafreniere could jump
In here and lend a hand.

On the Yamaha’s it’s not very hard at all, it takes me about 45 mins to pull both pumps, swap impellers and re install the pumps.

Yeah you can have a dealer do it but that is going to cost some dough.