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running @ high elavtion ?
- Thread starter zstevens
- Start date
High Elevation
Drop the prop pitch about 4 inches and you should be ok. With heavy loads and pulling skiers you might even need to go down another 2 inches.
I run at Big Bear Lake (elevation 6750) and this seems to work on almost every boat that I have tried it on.
On a new DI motor you do not need to drop as much because they compensate for altitude. My 225 HO Evinrude runs almost as good at high altitude as it does at sea level. The motor is a torque monster and my 21 br flies out of the hole with a 25 prop, even at 6750 ft. The rule of thumb is that for every 1000 ft you loose about 3 percent of the hp. Might be a little less with a DI motor.
Drop the prop pitch about 4 inches and you should be ok. With heavy loads and pulling skiers you might even need to go down another 2 inches.
I run at Big Bear Lake (elevation 6750) and this seems to work on almost every boat that I have tried it on.
On a new DI motor you do not need to drop as much because they compensate for altitude. My 225 HO Evinrude runs almost as good at high altitude as it does at sea level. The motor is a torque monster and my 21 br flies out of the hole with a 25 prop, even at 6750 ft. The rule of thumb is that for every 1000 ft you loose about 3 percent of the hp. Might be a little less with a DI motor.
Like Skip said, you'll need to prop down. Also, with carb motors, you're supposed to jet for the thinner air. Less air means you need to supply less fuel to the engine to make up for it.
Small altitude variations you can get away with jet settings, but large altitude variations you really should change jets out to compensate.
Worst case, you'll run way too rich, which is not NEARLY as bad as running too lean. So if it's for a short time, you probably can get away with not changing jets.
Small altitude variations you can get away with jet settings, but large altitude variations you really should change jets out to compensate.
Worst case, you'll run way too rich, which is not NEARLY as bad as running too lean. So if it's for a short time, you probably can get away with not changing jets.
I will have to look when I get home. But if I remember right its down 1 jet size for every 1000-1500 ft of elevation. This is right from the Mercury manual. The engine will be down a bit on power, but I would think a drastic pitch drop would be the last thing I would do. Need to get the engine running correctly for the elevation.
Test run the boat with the current set up, check the plugs to see if your running rich, then start dropping jet sizes. I worked on a boat last year that had this problem. We ended up dropping 3 jet sizes and the boat ran great with the prop that was on the boat when he got. When he first put the boat in the water we could not get it to plane out.
Ah the fun of carb motors.
Test run the boat with the current set up, check the plugs to see if your running rich, then start dropping jet sizes. I worked on a boat last year that had this problem. We ended up dropping 3 jet sizes and the boat ran great with the prop that was on the boat when he got. When he first put the boat in the water we could not get it to plane out.
Ah the fun of carb motors.
they are easy on a V-6. The in-line's are a pain as you can't get to the bottom carb. You can input your serial number in to mercury parts express and this will help with the carb numbers. ( also listed on the carbs) The merc site will also give you an exploded view of the carbs. They are not bad at all to change. You will have to different jets. The ones in the top and bottom carbs are the same and the middle is different.
I'm not trying to discount what everyone is saying, but 175, I'm with you all the way on this one. You need to jet the engine to run properly. We change props for performance preferances and to compensate for different loads, not to help an engine make up for what it's lacking due to atmospheric conditions. Could you get by at 6000 feet or so for a weekend trip? Yeah, probably so.....but why chance it? Do the right thing, and you won't feel like an @$$ later if you shell a powerhead. The jet thing is pretty easy, and your engine will live.
On a different topic, SKIP it's damn nice to see another Evinrude guy on here!! What hull are you running that rude on? Is it a Ficht engine or an E-tec? What's the setup and numbers like?
On a different topic, SKIP it's damn nice to see another Evinrude guy on here!! What hull are you running that rude on? Is it a Ficht engine or an E-tec? What's the setup and numbers like?
There was a previous post here that gave a place to look on Mercury's website I believe. You can never be sure which jet to use until you run the boat and check the plugs. Although every engine is somewhat different, you may even check out a couple other websites like Scream & Fly and see if there's anyone else out there running high altitude with a rig like yours. Just a thought?!
Even if you change the jets, you will still need to reduce the prop pitch. At 5000 ft, you will still lose10 to 15 percent of your power. Remember you have 175 hp at about 5500 rpm, at sea level, and about 75 or so at 2000 rpm. If you want to get out of the hole you must prop down.
You can also try an over the hub prop and spin the snot out of it, getting on plane. I have seen that work also. Good luck, Skip
You can also try an over the hub prop and spin the snot out of it, getting on plane. I have seen that work also. Good luck, Skip
bravo 1
Active member
i have a little exprience with altitude i bought a 2100br with a 2004 300x in 2005 now i know that this is a efi motor so the ecu will compenste for the altitude just as rejeting a carb will do the same. but my point is that even after you rejet your motor you will still have to drop i n prop size as well (probably 2 to 3 pitches ) the same boat ran a 27 temest plus at 400 feet and up at 4300 feet i ended up with a 24 pitch to get the whole shot and top end i wanted, so what i am trying to say is that if you wnat to get the best performance out of your motor rejet and a different prop is in order just my .02 cents worth of hands on knowledge.
Check ya later
Check ya later