Rejetting/new prop for 7400' elevation.

[logged in]

Hello All,

I have purchaced a new, old boat. 17 foot 1979 Larson Manta with a 1979 L6 Mercury 140

First, I tried it out at sea level ran around the local coast line other the cool starting everthing was great.

Next a trip up to Big Bear Lake (elev 6750) VERY hard to start won't low idle under 800 RPM
will trottle up to 2000 but will bog down after that.

The goal is to get it ready for an up coming two week trip June Lake Loop Elev 7400'

The current prop has no marking on it, Dia is around 14" but pitch is unkown.

The Plan, purchace new 14x15 or 17 pitch prop and rejet. my Seloc manual calls out main jets of .076 and air vent jets of
.094

What do you think?

Thank you in advance for your time and wisdom

 

[oldman570]

Re: Rejetting/new prop for 7400' elevation.

Rejetting the carbs is a must if changing elevation as the air is not as dense at higher elevations. Prop should be fine if you are happy with its performance now, and Dia. And pitch should be stamped on the prop mabe on the center hub.
Oldman570

 

[Sea Rider]

Re: Rejetting/new prop for 7400' elevation.

Sometimes will need to play with lower pitch same diam prop besides rejetting to compensate lost rpm working al higher altitudes. Place an induction tach if don't have one and check. That engine must be standard factory rejetted once at sea level use or could ruin the engine.

Happy Boating

 

[Chris1956]

Re: Rejetting/new prop for 7400' elevation.

Logged, Merc called for rejet of mains and backdraft, if elevation exceeded 5K feet. Idle mixture may be adjusted if necessary. Is the jet sizes you cited for elevation, or are they stock jets?

 

[logged in]

Re: Rejetting/new prop for 7400' elevation.

Hello Chris, the jets I listed are the jets called out for L6 140s in my ser# range for the elevation of 5000ft to 7500 in the Seloc manual #1408 Appeddix-A13

The only thing that has me wondering is that the 0-2500 elevation jets listed in the Seloc manual is Main Jets of .080 and Vent Jets of .098
These are not the jets listed in parts catalog from the folks at Crowley Marine and Marine Engine online parts catalogs is Main of .074 and vent of .090

I have not pull the existing jets from the carbs yet, to see what I actual have install now. I am assumeing that it has stock jets set for sea level. I will do so tomorrow

I am jut wondering if the jets listed in the Seloc manual are vaild.

 

[roscoe]

Re: Rejetting/new prop for 7400' elevation.

I would take the word of the Merc dealer/manufacturer over the word of SELOC.
Their manuals are filled with errors and ommisions.