Logo
FULL SITE MENU

High altitude and engine weight

G

gwg1

Member
"I have a 1981 Mercury 40 hp &

"I have a 1981 Mercury 40 hp (2 cyl) outboard and other than jets how should I adjust the engine to run 4500 to 8000 feet?.

Also, any one know how much this engine weighs??"
 
"Greg, I have a little more ti

"Greg, I have a little more time on my hands then Just-In-Time, so here's some numbers for you


The motor will weigh in at about 150 pounds (including the prop) and add an extra 10 pounds if it's electric start.

Depending on the altitude in the range you list, there are a couple of different jets.

Normal jet below 2500ft = .072, 2501-5000ft = .070 and for above 5000ft = .068

In addition, it's a good move to run a slightly smaller prop pitch. So if for example you are currently running a 13 pitch, move down to an 11.

High altitude engine models (and there are a few around) generally have different gear ratio's. You are not going to tear down your lower unit, so moving down a bit in prop pitch compensates for that to some degree..."
 
"from another site I posted th

"from another site I posted this
09:00:17 Quote From Merc Manual-Vent Jet
The vent jet supplies less than atmospheric pressure to the fuel bowl at mid-range, which results in improved fuel economy. If a jet with a smaller orifice is installed the mid-range fuel/air ratio will be leaner. If a jet with a larger orifice is installed (or jet is removed) the mid-range fuel/air ratio will be richer.


Rejetting Carb for High Altitude
If the engine is to be operated at an altitude higher than 2500 above sea level, it is necessary to rejet the carbs. BLA-BLA-BLA
2500-5000=main jet .002 smaller than standard
5000-7500=main jet .004 smaller
7500- and up=.006 smaller

Carb #
wmk 33-1 main=.072 vent=.096
wmk 37-1 =.072 =.092
wmk 38-1 =.072 =.092


All this info is for a merc 1983, 40hp, 2cyl, I don't have any other info but it should apply to your engine the same. Just find your specs and go from there."
 
Back
Top