Go Back   Maxum Boat Owners Club - Forum > Maxum General > Engines
Click Here to Login
Register FAQ Community Calendar Today's Posts Log in

Reply
 
Thread Tools Search this Thread Display Modes
 
Old 03-11-2009, 11:30 PM   #1
Ensign
 
Join Date: Mar 2009
Location: San Diego
Posts: 3
Default Merc 5.0 lacks power at altitude

2000 2400 SCR with 5.0 with Alpha 1. I live in San Diego and at sea level the boat operates great, last couple of years I've taken it to Lake Powell in August and the boat is a dog! I've tried every prop size known to man with no success. The engine just will bog down when any throttle is applied and acts like it's gasping for air. Should I rejet or consider swapping carburetors?

I had this same problem my 1900 Maxum I had that had a 150 Merc outboard on it. Sea level the boat was great, when I took it to Lake Powell nothing.

I believe Lake Powell is about 3800 - 4000 feet

Any help would be appreciated.
__________________

__________________
Smee Dog
Smee Dog is offline   Reply With Quote
Old 03-11-2009, 11:40 PM   #2
Admiral

 
seapuppy's Avatar
 
Join Date: Nov 2005
Location: Everett Wa
Posts: 4,681
Default

at those altitudes..the carb shouldn't be struggling...but ...if you have the 2 bbl carb then yes it's gonna choke alot....before doing anything to the carb while your up there...check to see if the choke plate is in the full open position....if not..see if it's binding any and try to work it loose...

if that still doesn't help..then you may need to rejet for higher altitude..which means a larger air jet instl....which will lean out at sealevel....so then you'd have to richen up again...one way to solve the problem is fuel injection...it will adjust the air/fuel mixture at any altitude...


oh...and welcome too the zoo...


Sp
__________________

__________________
Don't compare your life to others. You have no idea what their journey is all about.
------------------------
SSN683 Association member
Par Excellence
------------------------------
2008 Bayliner 340 - "Wild Whim"
--------------------------------------
I live in my own little world....but it's okay-they know me here!!!

Avid practitioner of the martial art: KLIK-PAO.
Tap-Rack-Bang

Anyone that sez "Size doesn't matter" has never owned a boat!
seapuppy is offline   Reply With Quote
Old 03-12-2009, 12:35 AM   #3
Ensign
 
Join Date: Mar 2009
Location: San Diego
Posts: 3
Default

Thanks
__________________
Smee Dog
Smee Dog is offline   Reply With Quote
Old 04-08-2009, 04:00 PM   #4
Lt. Commander

 
Join Date: Oct 2008
Location: Oshkosh, Wisconsin
Posts: 176
Default

I have the same problem with my motorcycle when crossing the mountains.
__________________
2006 Maxum 2000 SR3
SilveradoSS is offline   Reply With Quote
Old 05-15-2009, 05:09 PM   #5
Moderator

 
shrew's Avatar
 
Join Date: Apr 2008
Posts: 5,682
Default Re: Merc 5.0 lacks power at altitude

This sounds like a carb problem. It's esactly the same with dirtbikes and snowmobiles too (the extent of my experience with carburator tuning, but the principals apply to any carburated engine). I would contact a dealer in Lake Powell and ask them what the standard jetting for the Pilot and Main are in that area for your boat. He should be able to tell you the setting for the pilot screw and idle adjustment too. Compare to the standard jetting at sea level. I would bet that you're running rich. There needs to be a balance in the air to fuel ratio delivered to the carb. The pilot and main jets are staying the same when you relocate the boat, but the air is thinner at altitude causing the fuel in the fuel to air ratio to increase.

Once you have the right jet sizes and settings and you've purchased the jets, rejetting should be fairly straightforward.

Steve
shrew is offline   Reply With Quote
Old 07-22-2009, 08:32 PM   #6
Ensign
 
Join Date: Mar 2009
Location: San Diego
Posts: 3
Default Re: Merc 5.0 lacks power at altitude

Okay,
Just back from Lake Powell and the boat ran great! I dropped 1 size in jets and took an old 3 blade prop and had the pitch changed from 14 to 13.
Finally, after years of struggling with power, I was able to get up on a plane without any problems.

__________________
Smee Dog
Smee Dog is offline   Reply With Quote
Old 07-23-2009, 03:07 PM   #7
Moderator

 
shrew's Avatar
 
Join Date: Apr 2008
Posts: 5,682
Default Re: Merc 5.0 lacks power at altitude

Awesome!!!!!

Remember a Carburated Engine loses 3.5% power for every 1,000ft. of elevation even WHEN properly jetted for elevation. The curve will go up far more if left jetted for sealevel. So a boat jetted for sealevel can loose 17.5% power (based on a 5% loss/1000 ft.) or more when brought to 3,500 ft. Proper rejetting for altitude will minimize that loss. So, for example a 225 HP would loose 40 HP , or more, if jetted for sealevel and run at 3,500 ft. I've seen many people spend a significant amount of money trying to capture and increase far less HP.
__________________

shrew is offline   Reply With Quote
Reply


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
ENGINE REVS DROP zt260 Engines 3 09-15-2008 03:13 PM
fuel flow figures for 6.2mpi zt260 Maxum Owners General Discussions 4 09-07-2008 03:33 AM
Propeller Clutch Matangolas Engines 20 02-18-2008 05:04 PM
5.7L 230HP 16X16? BillinPA Engines 6 12-18-2007 10:44 PM
GRP Polish Webblet Maxum Maintenance 8 08-16-2005 01:27 PM

Powered by vBadvanced CMPS v3.2.3

All times are GMT. The time now is 12:19 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2024, vBulletin Solutions, Inc.