Boating "At elevation"...What's considered "high elevation"?!?!?

[Tyguy]

I typically boat at 5,400', and I just spent a week on Flaming Gorge at 6,040'. It's good to compare against other experiences in this thread and know my boat's performance is probably normal.

I've found our AR195 is sensitive to weight at these elevations. With just me in the boat she can hit about 46 mph, but with 1,000 lbs in people and equipment top speed drops down to around 38 mph. Getting on plane has never been an issue other than when I was pulling my brother on a tube, and he weighs about 270 lbs. In that situation I needed to put a couple of kids up front in the bow and even then getting on plane took a little time and distance. Once on plane top speed was about 25 mph.

Top speed of 38 to 40 mph equates to around 6,000 RPM. 46 mph is around 6,400 RPM, and that's as fast as the stock motor will spin at these elevations.

 

[sysinu]

I gotta say, there's a ton of posts on this topic, especially on facebook right now.

If you are boating in Utah, you need 4500' altitude pitched screws.
If you are boating in Utah, you should really consider doing a ribbon delete and replace it with a riva spacer.
If you are boating in Utah, you should really consider doing the K&N air filter replacement.

Last year, it just so happened that someone on the forum that posted about being at Rockport (I live across the street) and having performance issues and just so happen to get ahold of them. The before and after was unreal for them. Just removing the air filters and doing nothing else made a huge difference.

If you're at altitude and not getting over 7000 RPM on each engine, you have a problem that needs to be fixed. If you've done those 3 things that I mentioned and you still have an issue, then take your boat to the dealer because it could be a ton of issues (ranging from improperly gapped spark plugs, bad spark plugs, wear issues in your jet pump, water flow issues, problems with your impeller, etc). But of those 3 things that I mentioned, 2 of them are all things that just about anyone that is handy can do, they are low cost. The third item, your dealer will do (unless it was caused by damage to the impeller) for free as a warranty repair.

Also, if you're in Utah and don't mind running up to Rockport and you want me to show you the difference, I am more than happy to do so (and if it's a slow week for me, I'd probably be more than happy to help you make the modifications).


If you're not boating in Utah, but are at high altitude, then I would say the same things apply except for the pitch angle of the impeller. This will depend on altitude. It's a combination of the mods that you would do to get the best performance. I boat at 6,500' altitude with 4500' altitude pitched screws, ribbon delete and filter replacement and my performance is great. When I take my boat to Lake Powell (3500' altitude), I either need to replace my impellers with 3500' altitude screws OR, I keep my 4500' screws on and then just take it a hair easier on my hole shot (I blow it out with that combination).


Not trying to sound negative, but at some point you just gotta trust those of us that are saying these things make a huge difference at altitude .

 

[rex.niki]

I was just up at Flaming Gorge my boat wouldn't even go over 35mph what kinds of speeds do you get loaded or unloaded at the Gorge?
I'm thinking one of my pumps have gone south.
2016 242 Limited E series.

 

[Canuckjetboater]

I always thought I was fairly close to sea level. Been ding some research on the property my house was built on for another project and have located some topographical maps. Turns out I'm not all that close to sea level at home, or on the lake. House is somewhere around 875ft asl, and the lake is around 850f asl. I know some of the guys out west probably think this is nothing, but the guys on the coast clearly have a different perspective.

Looks like a drop of about .5 psi from sea level to my elevation. Roughly 1936ft elevation for every 1psi of pressure drop.

Air Pressure at Altitude Calculator <--easy calculator I found online.

At what point does this start to have realistic effects on boat performance? We're boating this summer on Douglas Lake which is about 920ft asl. I can do the math, but I'm looking for some real world examples/experiences. I doubt I have a problem compared to what I'm used to with only a few hundred feet difference in altitude, but I'm curious now when this starts to become an issue.

@2kwik4u ......the most important question is - is your engine operating at it's rated RPM? If it is a bit low not a big deal. If it is way too - which based on your information it should not be - then a re-pitch would be indicated.

 

[rex.niki]

@2kwik4u ......the most important question is - is your engine operating at it's rated RPM? If it is a bit low not a big deal. If it is way too - which based on your information it should not be - then a re-pitch would be indicated.

Both engines are around 6300 rpm about 35mph
I totally get the atmospheric pressure. Guess I didn't expect such a dramatic drop.
My impellers are stock as the boat used to top out at 42mph at 4300-4500 altitude Willard bay.
Boat is bone stock no ribbin delete or air filter changes.
The boat pulls to the left really bad so pulled the passenger side pump and it's coated with hard water and I have cavitation pits on the impeller.

 

[Tyguy]

I've been playing around with this on our '18 AR195 to see what kind of performance change can be had through different advice on this forum. I changed one thing at a time on the boat to see what it would do.

1. Changed the plugs at 30 hours with the same factory spec new NGK - no change in performance.
2. Found some visible gaps in the tunnel and intake grate sealant, but not sure if those gaps were just surface level. Sealed them anyway - no change in performance.
3. Removed the air filter box while on the water and tested speed and RPM before/after - minimal change in performance, about 1/2 MPH gain without the air filter box attached. I wanted to see if a K&N would make any noticeable difference, and with no air box, the change is too small to risk particles making their way into the engine, so I stuck with the factory setup. My stock filter has no visible contamination.
4. Waxed the full hull (never beached, just some minor wear on the gelcoat finish from the trailer bunks) - no change in performance.
5. Adjusted the CJS Super Ultimate fins and tested at 3 positions, including max down, min down, and pulling up at speed - 1-2 mph gain from max down position to pulling up at speed. On my boat the fins adjusted to max down produce noticeable spray that hits the back seats, and when set to pull up at speed they'll spray as the boat comes off speed, so I've settled on min down position which produces no spray and has minimum impact on top speed. I ski with this boat, swinging from 4 o'clock to 8 o'clock, and at the min CJS setting there's no perceptible movement of the boat's stern as I pull hard and accelerate across the back of the boat.
6. Checked impeller and ring condition - no nicks, dings, pitting, gouges, or other damage.
7. Checked for debris in the pump - no debris.
8. Played with different weight - this is clearly where the most performance change comes from at a given elevation. With 300 lbs of passengers (wife and I), wakeboard on the tower rack, a full tank of gas, and about 150 lbs of gear, our max speed at 6,000 ft of elevation was about 44 mph to 45 mph with no wind and smooth water at Flaming Gorge last week. Water temp was 72 F, air temp 75 F, and engine was relatively cool. Upped the passenger weight to 1,060 lbs and our top speed bogged down to 35 mph in similar conditions, and was slow to plane (200 lbs up front, the rest distributed around the rear seats). I cruised at 30 mph without difficulty and had a few hundred RPM left in the range to help through the turns.
9. Water/air/engine temp - this is another area that makes a big change. As the water, air, and engine heat up I see a drop in speed.
10. Elevation - this is another big area where change in noticed. Even jumping from 5,400 feet to 6,100 feet can be felt with a 2 mph difference.

What I haven't tested yet is a different impeller. The dealer re-pitched my stock impeller prior to delivery but hasn't told me exactly what the pitch is. It's apparent the impeller is pitched for our altitude and to produce more thrust out of the hole. They're pushing hole shot over top speed, which is good for water sports, and the boat has no problem pulling me out of the water even with several variables playing against it, like warmer water, warmer air, hot engine, high elevation, 700 lbs of passengers besides my 165 lbs behind it.

I could change to a different impeller with different pitch to gain more RPM and in theory top speed, but I think it would sacrifice hole shot and towing. If so, it's not worth it. I'd love to have my cake and eat it, too, though. If I could keep hole shot and still bump up top speed without impacting engine longevity and reliability, then I'd be willing to invest some bucks. I don't want to go as far as a new super charger with more boost, though.

The Lucky 13 cone is something else I haven't played with, and I probably won't since cavitation hasn't been much of an issue. It does occur, just not frequently enough for me to worry about it. One thing I was able to learn from cavitation is that the engine has the ability to hit redline for that brief second until either the water suction catches up or I back off the throttle just a bit.

Anyway, that's what I've learned so far.

 

[Canuckjetboater]

Anyway, that's what I've learned so far.
[/QUOTE]
@Tyguy ....WOW - now that's a meaningful set of authentic test statistics. Like you I found the huge difference air density, not just hot vs cold at 'sea level" elevations but of course in thinner air "at altitudes". As well, temperature makes a tremendous difference too. I'm sure you know this but be careful if you bring that boat down to sea level on a trip because with the re-pitched impeller it could allow your engine to RPM past it's red line even if Yamaha has some sort of governor in place. Great stats - I bet a lot of forum members will be using these to compare!

 

[Tyguy]

@Canukjetboater ...Thanks! Hopefully it'll help someone, and good point about watching RPM when I drop elevation.

One additional test I forgot to add to the list:

11. Adjusted throttle cable linkage to hit the stop with the throttle box lever pushed all the way forward - no change. There was about 1/8" in there just like everyone else has reported, and removing that slop didn't make any change in max RPM or top speed. All it did was increase the "dead pedal" feel so I had to pull back on the lever more before RPMs started to drop.

 

[rex.niki]

Found that my problem was more related to maintenance issue, will attach pictures, I'm back to seeing low 40's around 4300 feet. 42mph was my max for the day.
2 people 44% fuel
400+lbs of gear
89F air temperature
82F water temperature
Muggy day just a guess 70% humidity

We wet slip out boat during the summer, we pull it out and clean the haul rinse the pumps.
After removing one impeller we found heavy hard water deposits see pictures attached.
After some folic acid and a beer or two I was able to get the pump housings and impellers clean. They do have a bunch of cavitation burns and the impellers will need to be replaced at a later date.

 

[sysinu]

Both engines are around 6300 rpm about 35mph
I totally get the atmospheric pressure. Guess I didn't expect such a dramatic drop.
My impellers are stock as the boat used to top out at 42mph at 4300-4500 altitude Willard bay.
Boat is bone stock no ribbin delete or air filter changes.
The boat pulls to the left really bad so pulled the passenger side pump and it's coated with hard water and I have cavitation pits on the impeller.

stock screws are not going to work at willard unless your dealer had them repitched when you bought it from them. The difference between 3500 and 4500' screws is pretty dramatic (I set mine side by side a while ago and looked - I have a set of both, one for powell and one for rockport). I gotta tell ya, doing the ribbon delete is going to help your holeshot way more than you'll ever realize without doing it.

I recently had a yamaha owner with a similar boat to mine go for a ride with me and he said my holeshot was like a tesla in insane mode compared to his boat. At altitude, it makes a world of difference.

 

[Nightmare]

Hey everyone. We are up at Huntington Lake California. Elevation is nearly 7k (6955’).

I was pulling my daughter on a tube today and notice that the box MAX RPM is only 6k. Is that about right for a 2011 Yamaha 242 LS?

I didn’t notice the max RPM last year at Shaver Lake (5627’). But I will be checking it out tomorrow.

Huntington is nearly 100% capacity for another 3 weeks.

 

[Matt Phillips]

That sounds about right. On Tahoe (6225) I top out between 6200-6300 rpm.

 

[Nightmare]

Thanks. I’ve tried to upload this photo twice. The internet coverage is not good

The lake is a little cold. But not crowded at all.