Altitude Fuel Adjustment?

[sawhorseray]

We’re headed to Buckboard for eight days in a week from today, I live right about sea level. I know at 5000’ Lake of the Woods last year might boat ran like a rat, could barely plane. Someone told me my 2015 Yamaha T-60 EFI motor should make the adjustment for altitude automatically, which I doubt. Does anyone have any insight as if I have to pop the bonnet and make some kind of richer / leaner fuel mixture adjustment. Of course I have no idea how, but of friend of mine will be there at the same time and he knows a lot more than the nothing about boat motors than I do. It seems to me that if the wind starts to blow it would be a good idea to get off the water as fast as possible Thanks for any advise, can’t wait to get there! RAY

 

[0 DARK 30]

I would change the propeller to a lower pitch, don't adjust fuel.

 

[BAGGEDLB7]

If it's efi it will adjust by itself it is computer controlled. When you couldn't plain were you getting the rpms you normally do? If not like dark said you probably need to re prop.

 

[Ryart]

Regardless of whether your motor makes an adjustment for altitude you lose about 3% of your power per 1000' in elevation gain... So you'll be down about 20% at the Gorge. My 200 HP runs like a 160 HP here and runs like a R@p#d Ape when I take it to sea level/offshore. Being correctly propped is the bigger issue. My boat came with a 19 pitch aluminum and would barely plane at the Gorge... Runs great with a 15 pitch SS prop now. I'd suggest going down at least two sizes in prop pitch.

 

[dubob]

Altitude adjustment

Ray,

Your motor DOES compensate for altitude - believe it. And what has already been stated, if you want to improve your performance at higher altitudes you need to change the prop pitch. Here is a link to a good article on this - Understanding Propeller Pitch - and a quote from the article: "If you're changing pitch on a recreational boat, remember that each inch of pitch is worth about 200 rpm. Lowering the pitch will increase rpm and vice versa. For example, going from a 23 pitch to a 21 pitch will increase engine rpm by about 400 revolutions."

As you go higher in elevation, you will notice a decrease in engine rpm's with your current prop. If you know what the decrease in engine rpm's actually is at 5000 feet elevation, you can determine the amount of pitch decrease you need. You may want to check with Yamaha directly and ask for some technical advice on this as they may have the data to correctly advise you on how much pitch decrease is required. Your dealer may also know if you have higher elevation lakes in your local area that they deal with on a regular basis. And remember, your motor has an upper rpm limit that you absolutely don't want to exceed, so be sure to choose a pitch that will increase the rpm's but not put you over the max for your motor.

 

[sawhorseray]

Thanks to all for the great advise. I'm going to contact Yamaha as Dubob suggested and see what they have to say as far as what I have on now and what I might need to improve performance. Changing the prop looks to be real easy, I might even read the manual. The folks at my local West Marine always seem pretty darned knowledgeable, I think I'll head over there right now and see what I can find out. Thanks again! RAY

 

[MackayGuy]

Ray,

Your motor DOES compensate for altitude - believe it.

Sorry, but I don't believe it. A naturally aspirated engine will lose HP at higher elevations. The EFI can adjust the fuel/air mixture, but doesn't boost the intake pressure to compensate for altitude. The EFI is better than carbureted, but can't make up the loss of atmospheric pressure. If your motor does compensate for altitude you wouldn't need to change prop pitch....yeah?

 

[Bduck]

I recently bought another boat(Feb) and been ironing out a few issues with things. This week is the performance of the Yamaha F150. I bought the boat at sea level in which its performance was really good with a 20 pitch prop @ 42mph and rpm's nearer to 5800. Bringing it home to altitude the rpm level was lagging at 4200wot @ 36mph. These F150 motors are rated to perform at or near wot 6400rpm. I tried a neighbors 16 pitch prop( we both have the same motor) which it took me up in rpm's quite a bit from 4200 to 5500wot and I was able stay in general area of 34-37mph without sacrificing a lot of the top end of speed. I now have a better idea of what I need so I ordered a ss 15 pitch to up the rpm's more. Sometimes your down pitch a prop for your area without sacrificing much at all on speed while changing wot rpm a very little. There is a wide array of props on the market which will help you decide your direction. Also to aid in in the performance of an engine of any type the standard day condition 29.92 barometric, 59F @ sea level, adding a little humidity to this is like a water injection further enhancing performance. From the standard day condition a chart will only go down in temp range to a lowest peak and anything beyond that will stay the same and same goes for the opposite end when peak above. Obtaining a chart from the manufacturer of an engine for each change in these stats might be difficult. However, if your motor is computer controlled these stats are built in taking out the guess work. You don't have to adjust anything but repropping.

 

[sawhorseray]

At this point I've ascertained that I have a 10 & 1/2" X 13 Turning Point black painted SS propeller. I trust the guys that do my yearly service, this boat and the 22' Proline I used to own. They are closed on the weekends, of course, but I'll see what they recommend come Monday. Thanks again! RAY