Adjusting for altitude change.

[Ianlinares]

Hi Folks,
Need some help I just got a 1987 Sea Ray with a 4.3L V6 OMC Cobra, and I have only run the boat at lake Piru so far. Piru sits at about 1000 ft above see level.
I have a house at Big Bear Lake and I want to take the boat up to Big Bear but the elevation there is over 6000 ft. Would I need to make adjustments to the Carb? And how do I do that? Pretty new to Carbureted engines.

Thanks

 

[Scott Danforth]

yes.

depending on the carb, your most likely changing jets

 

[Bondo]

Ayuh,..... Welcome Aboard,.... Donno 'bout the carb, but yer gonna wanta go to a smaller prop,....

Yer not gonna have the horsepower ya got at sea level,....

 

[bruceb58]

My GF has a house in Big Bear too. Also have a house in Tahoe which is close to the same elevation. For Tahoe, I don't bother re-jetting and the main reason is also use it at sea level. If all you are ever going to do is use it at Big Bear then you may want to re-jet. In any case, you need to drop a couple inches of prop pitch.

You have a dock up there? We are in Pine Knot.

 

[Ianlinares]

We don't have a dock our house is in Sugar Loaf. Renting a slip for a couple days doesn't seem to bad we only go up 4 to 5 times a year.

So when you guys say re-Jet the carbs, do you mean I buy a larger nozzle jet, and replace the stock jet? I will defiantly pick up a new Prop for big bear.

 

[jimmbo]

Recalibration varies depending on the carb, it might just be jets. It might be jets and metering rods, primary and secondariy if a four barrel. Change to the power enrichment set point might also need changing. As mentioned earlier, for a trip to mountains, just reprop 2-4 inch lower. Long term use at higher alt, recalibration of carb will save some gas, but then a return to lower altitudes will require a return to stock

 

[bruceb58]

Do you ever use the boat at a lower elevation than Big Bear? If you do, I wouldn't bother re-jetting.

 

[Ianlinares]

Most of my boating will be at lower elevations. I won't be leaving my boat in Big Bear. I just want to bring it with me over spring and summer the few times I'm up there. Thanks for the help guys. I will start with just a Prop change.

 

[bruceb58]

When you rent a dock, which marina do you rent at?

 

[Ianlinares]

Haven't taken my boat up yet. Heard Capt John's Harbor has best pricing. Pine Knot or Big Bear Marina would be the most convenient as its right below downtown. What do you recommend?

 

[bruceb58]

Capt John is over in Fawnskin which is more of a drive. PineKnot has the best facilities which is also the closest to you but is also the most expensive. I own a slip in PineKnot myself. A lot of people use Pleasure Point or Holloways.

Right now at Pine Knot they have all the docks outside the breakwater since the water is so low. I am not sure where the docks are they rent out on a daily basis but they may be on the outside anyway. The nice thing about Pine Knot is that I believe it is way more secure than some other places because they use key codes to get on the slips.

At least for owners like me, PineKnot has its own launch ramp. Not sure if short term renters have access to it. Right now the water is too low to use it though.

 

[Ianlinares]

Hopefully we get some rain and snow this winter.

 

[Ianlinares]

I checked my prop. I currently have a 14.5 x 19 prop. So for altitude should I drop down to a 14.5 x 17?

 

[bruceb58]

I checked my prop. I currently have a 14.5 x 19 prop. So for altitude should I drop down to a 14.5 x 17?

As long as you have proper WOT range with your present prop, that should work. With an older boat, I would drop 2 inches when I went up to Tahoe.