What a Drag! How to Add Pep to Your Boat for High Altitude Performance

What a Drag! How to Add Pep to Your Boat for High Altitude Performance

The lakes may be hard to reach, but the views are breathtaking, the waters clean and there's plenty of fish to be found.

"Ain't no mountain high enough" ... wait a minute, let me get out of the clouds and come down.

So... you wanna take your boat on lakes thousands of feet above sea-level? Well, I'm here to help.

What Is Classified as High Altitude?

For a majority of people reading this, you may not care about this topic. But for the small percentage of people who live at High Altitude (HA) or are going to move to a place with high altitude, this article is for you.

What Is Considered High Altitude?

For humans, at 8,000 feet above sea level or higher, you'll experience altitude sickness. However, for motors, it can be as little as 1,000 feet above sea level.

Examples of Different High-Altitude Lakes

Using my home state of Utah as an example, there are a plethora of high-altitude lakes. In the Salt Lake Basin, you have Utah Lake and Willard Bay. Then there's the Great Salt Lake, but we don't really boat in that one ... too salty! Less saltwater boating means less flushing with a de-salt product and rinsing down decks and gel coat with boat soap.

These lakes sit at around 4,000 feet above sea level. Next, you start moving up to lakes like Bear Lake and Flaming Gorge - both over 6,000 feet in elevation -  which is quite a difference compared to sea level.

Another personal favorite high-altitude lake is Idaho's Island Park Reservoir, among many others that you'll see below.

  • Lake Tahoe - California/Nevada - 6,225 ft above sea level

Explanation of Horsepower Loss at Elevation

Before we go too far, I'll explain the math behind horsepower loss at High Altitude. 

It's basically like this: If you or a friend lives somewhere like California or a similar place, you're used to the sea-level elevation. When you suddenly go up to a mountainous region like Utah, Colorado, Wyoming, you feel winded, lack energy and can even experience altitude sickness.

I personally have experienced this. Traveling to South America, my flight took me to La Paz, Bolivia, which sits at 12,000 feet above sea-level! An absurd elevation which actually made me sick, suffering from lack of oxygen.

This is the key. The higher you go, the less oxygen there is. And if you lack oxygen, a lot of functions start to go haywire. Remember, we need oxygen.

So if the human body requires oxygen, then what about your boat's internal combustion engine? It too requires oxygen to ignite fuel to generate power.

Simply put—when you have less oxygen, you have less power (even if you're a boat).

Some Simple Math to Explain

Remember I said that I wanted to use math? Don't worry it's simple math, nothing too complex. I actually have Yamaha motor corporation to thank for the math. They did the hard work to calculate this.

To put it simply, for every 1,000 feet in elevation you go up, you will lose 3% of your horsepower.

For example:

  • 4,000 feet = a 12% loss of horsepower
  • 6,000 feet = a 18% loss of horsepower

Ok now plug in some horsepower numbers: 150 hp outboard at 4,000 feet will lose 12% of its horsepower.

150 x 12% = 18. / 150 - 18 = 132 hp

That 150 has now suddenly become a 132 hp instead at 4,000 feet. What about 6,000 feet?

150 x 18% = 27 / 150 - 27 = 123

Can you see where this is going? The higher you go, the horsepower loss is more significant.

For example, I have one customer who lives in Colorado. The closest lake to his home sits at 9,000 feet. 9,000 feet! 

That's an astronomical height that results in a 27% horsepower loss! A 150 hp outboard at 9,000 feet is suddenly a 110 hp motor. That's a huge loss and there's no easy solution to it.

The end lesson here? Don't buy under-powered boats if you live in high elevations. A 19-foot boat with a 115 hp or even a 90 hp outboard still works well. But the same boat at 4,000 to 6,000 feet? It's essentially a big floating turd as it won't go anywhere. I don't mean to be blunt, but I've seen and dealt with it on countless occasions with my customers. 


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What Is High Altitude Boat Performance?

High Altitude boat performance is when you get the maximum performance from your boat when you boat at the best lakes around. Joking aside, I'm sure there are great lakes at lower elevations, but some of the lakes way up here are just plain gorgeous!

Are you getting all of your Boat's Performance?

This is a tough question to answer, but the first place you have to look is the prop.

The second question, which isn't as easy to fix, is: does your motor have electronic fuel injection/direct injection? If it does, it'll certainly help a lot. If not, you'll have to mess with jetting, which I'll touch on later.

The third question is: does your motor have enough ponies under the cowling? Remember the math section? If you fish at H.A., having a bigger and badder motor on the boat will negate the percentage losses.

For example, 150 hp at 4,000 feet is actually like 132 hp. If the same boat had a 115 instead, then at 4,000 feet, it's actually 101 hp. That 150 still has a full 31 hp more which will only help.

You can always slow down, but it's tough to accelerate when the power isn't there.

The last solution is to have a motor with a turbo/supercharger. I'll touch on this topic more down below.

How do you know you're getting optimal performance?

This is critical to know for many reasons. If you're not getting optimal performance, then it not only isn't fun, but it can cost more money in fuel and unnecessary wear and tear.

The number one rule of thumb when it comes to optimal performance is what is your WOT RPM? (Wide Open Throttle's Revolutions Per Minute)?

For outboard motors, you want to be between 5,000 to 6,000 RPMs at WOT.

For stern-drives, you want to be in the 4,000 range.

For the other styles of inboards and jet-drives, refer to your owners manual as there are too many variations to give a recommendation.

When you're testing your boat and at WOT, if you're not in the recommended RPM ranges, you know you're not at optimal performance. Granted, if your prop's damaged, it'll be misleading for your test so make sure your prop is in tip-top shape. The same can be said if the boat hasn't been maintained properly.

How to Overcome High Altitude Challenges

Before I dive into this topic, you'll want to ensure the few variables with your boat.
  • Make sure the prop(s) are in prime condition.
  • If you don't remember the last time you had a tune-up, consider getting one.
  • Run a WOT test on the body of water you visit the most often. I recommend running it with your typical boatload of people, gear, food, cleaing products, boat accessories, anchors and/or pirate equipment (maybe not the pirate equipment, but if you have it, that's pretty cool)

How to Get the Most Out of Your Boat When Living High Altitude

The end goal here is to improve your acceleration and/or top end speed. To do so, follow the aforementioned list above, then get ready to learn prop dynamics.

Best and Most Simple Solution Is Changing Props

The most effective solution to high altitude is changing the prop. As you rise in elevation you need to go down in pitch. The inverse is true as you go down in elevation.

Every boat, lake and situation is different. When in doubt, talk to the local dealer. They'll be familiar to the situation at hand.

The higher you go, you'll have to keep dropping in pitch, but you'll still lose some performance even when you get the RPMs in the proper range. Because there's less oxygen, it means less power out of your engine.

There's one solution to this unique problem - but limited options - and that's to purchase a boat with a supercharger or turbo.

How Turbo and Super Charged Engines are the Best High Altitude Solutions

So how does a charged engine overcome HA and why are they the best solution to HA problems?

Put simply, when an engine has a turbo or supercharger, it inducts air. This means it forces air into the engine to give more performance. In the case of high altitude, your motor doesn't suffer horsepower loss.

Remember the math from before? Even if you have the motor at 4,000 feet you won't lose 12% of your hp. Now, keep in mind turbos/ superchargers are not perfect. You'll lose some power but the loss is not as profound.

One side note: The majority of high-performance boats have superchargers. Turbos are out there, but they're more uncommon.

A Hard Pill to Swallow: Your Boat Will Never Perform at High Altitude Like it Can at Sea Level

Despite all the helpful information, there's one thing you have to keep in mind: No matter what you do, no matter what boat/motor you buy, no matter how much weight you shed from the boat, you will lose performance at High Altitude.

I've seen it with supercharged motors as well and it is a hard pill to swallow. But by following my advice, advice from local dealers, and tips from your local boating friends, you can minimize the HA effects. Keep this in mind, and you won't be disappointed. 

How to Overcome High Altitude Challenges with Older Carbureted Engines

If your engine is fuel-injected, then you can skip this section. However, if you have a carbureted engine, this section is for you!

What Are Jets?

Jets are small brass fittings with holes of varying size in the center. This is where the fuel/air flows, allowing the engine to run at optimal performance with the proper fuel/air mixture. Too much fuel and it dies. Too much air and it can run lean and cause other problems.

How to Pick the Right Jet

As you rise in altitude, you need to lean out the jets. The reason for this? There's less oxygen and if the motor gets too much fuel, it won't run right.

Go too lean, however, and you can risk starving the motor. Worse, if you have a two-stroke pre-mix outboard, you can risk it not getting enough oil and burning up the crank bearings.  

Jets are difficult to change and downright challenging to find the right jet for where you run. H.A. is not the only factor. Temperature, humidity, and other factors will play a part in picking jets.

To keep it simple, my absolute best suggestion to picking the right jet is to ask a dealer of your motor who lives at HA. Talk to older grizzled mechanics and they'll lead you in the right direction. If you don't feel up to the task. they'll be able to handle the task for you.

If you don't have a dealer or can't find one, then start richer and slowly work your way down until it's running right. This may take several attempts, but don't give up.

If you want to give up, then it's time to upgrade and get a fuel injected motor.

Air Fuel Adjustments Are Needed When You Change Elevation

Carbureted motors will have an air/fuel mixture screw. If you're only making a slight change in elevation, you can open or close this screw to make up the change. If you are unsure where this is, refer to your owners manual or dealer for assistance.

Closing Thoughts

High-altitude boating can be challenging (if not downright frustrating). I've met many people who move from coastal areas up to the Rocky Mountains and don't understand why their boat—that ran great before—now runs like crap.

Remember to check the prop first and change if necessary. It's the simplest and most straightforward solution for adjusting to a higher elevation.

The next best solution is higher horsepower. After that, you might have to address additional solutions. Or pack up and move. Hey, I didn't say I was going to sugar coat it. Plus, I need more room at my beautiful Bear Lake, so moving is a legitimate solution.