Any Improvements to CM-Tec Hulls Since 2018??

[kestrel452]

The Kawi Ultra hull is known to be very durable and good handling in the rough but the 160 HP engine might not be powerful enough for you.

I would be fine ponying up for a 2023 Ultra 310LX, however, I am still unsure how much worse it is on fuel economy (if at all) compared to similar S/C craft such as the SVHO or GTX 300. I recall Watercraft Journal saying the Ultra 310LX is a gas guzzler even compared to both of those... Anyone have any insight as to whether that is true? I think i'd be fine with any craft so long as its best cruise could get it at least 100 miles of range with 10% reserve remaining.

The funny thing about that though, is I'd probably still get more useful range out of a Kawi 310 just by virtue of it having a slightly larger tank, and the apparent lack of a fuel gauge/alarm that makes half the actual tank practically unusable.

[Mr. GP1800]

I would be fine ponying up for a 2023 Ultra 310LX, however, I am still unsure how much worse it is on fuel economy (if at all) compared to similar S/C craft such as the SVHO or GTX 300. I recall Watercraft Journal saying the Ultra 310LX is a gas guzzler even compared to both of those... Anyone have any insight as to whether that is true? I think i'd be fine with any craft so long as its best cruise could get it at least 100 miles of range with 10% reserve remaining.

The funny thing about that though, is I'd probably still get more useful range out of a Kawi 310 just by virtue of it having a slightly larger tank, and the apparent lack of a fuel gauge/alarm that makes half the actual tank practically unusable.

The 310s are pigs for fuel use. It’s why I picked Yamaha over the Kawasaki

A group of 4 of us made the same trip. 2 of us on GP 1800s one RXTX 300 and a Kawi 310. All 3 of us went the same distance. Made a fuel stop. My GP took 8.5 gallons. The sea doo took 9.5. The Kawasaki took around 12 gallons. That’s insane if you ask me.

[Team Bilford]

I would be fine ponying up for a 2023 Ultra 310LX, however, I am still unsure how much worse it is on fuel economy (if at all) compared to similar S/C craft such as the SVHO or GTX 300. I recall Watercraft Journal saying the Ultra 310LX is a gas guzzler even compared to both of those... Anyone have any insight as to whether that is true? I think i'd be fine with any craft so long as its best cruise could get it at least 100 miles of range with 10% reserve remaining.

The funny thing about that though, is I'd probably still get more useful range out of a Kawi 310 just by virtue of it having a slightly larger tank, and the apparent lack of a fuel gauge/alarm that makes half the actual tank practically unusable.

Wouldn't 160HP on an Ultra be kinda a dog on the bottom end?

Range may be better on the Ultra than you think. I believe it has a bigger tank than the others. More expensive to run, but I bet range is still in the same ball park.

If you want the Ultra hull, get the 300 and just keep the RPMs down off the SCer. That will give you the N/A range that you are considering in the 170, but more fun when you are not trying to save fuel.

[kestrel452]

The 310s are pigs for fuel use. It’s why I picked Yamaha over the Kawasaki

A group of 4 of us made the same trip. 2 of us on GP 1800s one RXTX 300 and a Kawi 310. All 3 of us went the same distance. Made a fuel stop. My GP took 8.5 gallons. The sea doo took 9.5. The Kawasaki took around 12 gallons. That’s insane if you ask me.

Nothing against anyone here or WCJ, but something tells me these differences in fuel range/consumption on the Ultra 310 vs the SVHO and GTX is being exaggerated. They're all around the same horsepower, and the Kawi boasts a 19% larger fuel cell...something isn't adding up IMHO

[K447]

- differences in fuel range/consumption on the Ultra 310 vs the SVHO and GTX is being exaggerated.

They're all around the same horsepower and the Kawi boasts a 19% larger fuel cell...

Supercharged PWC tend to consume more fuel, in part due to the ease with which they can cruise at higher average speeds.

The Kawi 310 is manufacturer rated to consume 24 GPH at full throttle. This translates to a cruising range of 54 miles or 49 minutes at WOT.

Information regarding part throttle cruise fuel burn rates at various different cruise speeds is generally unavailable or limited to one hull/engine combination.

Hull design and hydrodynamic drag consume almost all the engine power being produced at cruise speeds. If the hull requires more power to maintain a certain speed through the water then that hull+engine combination is going to consume more fuel per minute, per mile. The big Kawasaki hull is considered to be very good in rough water riding but the hull is also considered to create significant water drag.

The Yamaha and Seadoo hulls may need less power for the same cruise speed which will translate into less fuel burn per minute, per mile.

The engines themselves have different fuel efficiency. The Kawasaki supercharger may consume more engine power to run the supercharger which means fuel consumed just to power the supercharger, compared to the gear driven centrifugal Yamaha and Seadoo superchargers.

The Yamaha SVHO engine is considered to be fairly fuel efficient overall during mid-range cruise even with the supercharger.

The combination of a hull with more drag and an engine that is somewhat less fuel efficient might make for a fuel burn delta at cruise that eclipses the 19% larger fuel capacity in the tank.

Not that many years ago the general consensus was that on a long cruise ride the supercharged Seadoo riders would be looking for a marina to refuel before the Yamaha SVHO riders. A Kawi rider that might join for a ride would also be happy to refuel when the Seadoo were in the marina, but perhaps was less worried about 'running out' of fuel before the group arrived at the marina.

[ptscon]

Not that many years ago the general consensus was that on a long cruise ride the supercharged Seadoo riders would be looking for a marina to refuel before the Yamaha SVHO riders.

Probably due to the fact that Yamaha has been using 70L fuel tanks for a long time vs Sea-Doo that had only 60L until very recently. The actual fuel consumption is probably very similar.

[K447]

Probably due to the fact that Yamaha has been using 70L fuel tanks for a long time vs Sea-Doo that had only 60L until very recently.
The actual fuel consumption is probably very similar.

That is a common posit but the range differences were often noticeably greater than the fuel tank capacity difference.

Some of the Seadoo in the riding groups had 60 liter fuel tanks and some had 70.

All would begin the ride with ‘full’ fuel tanks. At each fuel stop we could see the fuel refill amounts. The Seadoos would typically take litres more than the Yamaha to refill. The longer the ride before the fuel stop the greater the delta in refill required.

Multiple factors affect fuel consumption and fuel range. Hull shape, engine power and fuel efficiency at cruise, rider throttle finger activity, weather, water and wind conditions, fuel tank capacity. And so on.

Semi-related story;
When I am leading a tour ride, before the ride begins I estimate when each ski is likely to first initiate a Low Fuel warning, and how much farther the group can ride before actually coming close to running out. Usually the group is our two SVHO GP1800 plus a few Seadoo and perhaps some other Yamaha models.

Last summer a group of four of us toured Temagami Lake. Temagami to Surveyor Lake, round trip approximate 120Km with lots of side jaunts into various bays. Total ride distance was estimated (by me) to burn roughly 90% of each fuel tank. Tanks were stuffed to the brim before launching.

Two Seadoo Spark 2-up with tunes (~110hp) and our two GP1800 SVHO with Stage 1+ tunes. On the way back to the launch ramp each Spark rode for about forty minutes with Low Fuel warning active. Back on the trailer each Spark took 29 litres to refill. Rated fuel tank capacity is 30 liters

Despite the greater fuel burn rates of the GP1800 SVHO the Low Fuel warning did not sound until we were less than ten minutes from the launch ramp. I forget how many liters each wanted for refill but there was probably ten liters in the bottom of each fuel tank at the end.

[TheDt]

Can only share my experience on the one ski, but after 700+hrs on a 2019 seadoo gtx 155 NA.... about 6 mpg is the average. All open ocean and ST3 hull has been great for me, but dont have much to compare it to aside from some rental time on other skis in a bay.

[K447]

Can only share my experience on the one ski, but after 700+hrs on a 2019 seadoo 155 NA.... about 6 mpg is the average.
All open ocean and ST3 hull has been great for me -

On the Temagami trip the two Sparks averaged about 9.4mpg while the two SVHO GP1800 would be around 4.7-ish mpg.

Cruise speeds most of the time, maybe 35 to 40-something mph (trying to not push the Sparks near top speed).

When cruising with only supercharged PWC our cruise speeds tend to be in the 50mph ranges.

[Green Hulk]

Was that the yellow one that was all over FB? It didn't hit anything?

Yes that's the one. It didn't hit anything other than constant pounding in waves.

[conroe]

I thought, it showed him hitting a red course marker. Could be wrong.

[GreenHulk Jr]

I thought, it showed him hitting a red course marker. Could be wrong.

I think you have this ski confused with another one that sank recently. There was a video of another RXPX hitting a course marker; the counter weight swung up and cracked the hull.

[dcuhpw]

I recall seeing a purple one hit a marker during a race and cracking the hull. There are just too many factors to consider here.
Here's my .02: the ST3 hull isn't bad in the rough but I immediately felt the bow hunting. Now this is me coming from other skis and an avid rider for 20 years now. To a person who just jumps on a ski for the first time they may not notice it. I did the Riva sponsons and they did greatly improve the feel but it was never 100% gone. Listing to one side was another issue I had with my ST3 hull. I've also ridden the Ultra hulls extensively in rough seas. They do well overall but have a very nose-down approach to any wave and will shovel water over the front in a hurry. Slow speed in heavy chop was nasty on the kawi's as was the seat design. I've ridden the 260 and 310R. The R was better but still uncomfortable for long day trips. Few months ago I picked up a 13' RXPX. Hands down much better handling than any other hull for my style of riding. Its drawback is riding 2up as it doesn't like to respond to steering input as well at lower speeds. There is always going to be some compromise with hull designs.
As for CM tech, I'd personally have no issues taking out an st3 hull in heavy chop far from shore. These "failures" that have been posted, often don't give the whole story. Not to mention, even a nasty trailer ride could cause hull damage to a ski before it even gets in the water.