Altitude question.

[ilmostro99]

Hello everyone, got a quick question about taking my boat to a high elevation lake.
Info:
'99 Sea Ray 190BR
5.0 carbed Mercruiser V8
Alpha 1 lower unit.

Going camping this weekend at a lake about 7,000'. Boat is set up for sea level. I've had it at a lake at 5,000' before and it really struggles to get up on a plane. I've read that getting a lower pitch prop will help, but not really interested in spending $100+ for just a day or two on the lake. Is there a mixture screw that can be adjusted to give just a little more power? If so, can it easily be set back for 0'-400' (example: just turning it back the 1/2 turn or so that I adjusted it for altitude)? If not, will running it rich for a couple days cause any harm?
Not going to be wakeboarding or anything. Mabye just some fishing and pulling some small kids around in a tube for a while.
Thanks,
Erik

 

[Kainon]

Re: Altitude question.

You would need to do 2 things:

1. Lower pitch prop say from 19p to at least a 17p if not a 15p (depending on boat load)

2. Lean the Idle Mixture of the carb, you should also drop down a size or 2 on Jets, but, for only a day, it wouldn't matter.

The best thing you can do is drop pitch.

If you had a Piranha Prop you could call up and get a lower set and return them providing they weren't damaged, just pay shipping.

Running an engine rich isn't good for you or the engine.

 

[45Auto]

Re: Altitude question.

There are no magic mixture screws you can fool with on your carb that will make a bit of difference. Leaner jetting/needles is the only way to get the fuel/air ratio back where it needs to be to maximize your power, but as pointed out above, it's not worth it for one day.

The "idle mixture" screw is called that for a reason. I would be surprised if your idle is affected at all. Can't count how many times I used to drive my carbureted Pontiac from sea level to 7000'. Never noticed any difference in the idle. Don't mess with it if your boat idles OK.

 

[HT32BSX115]

Re: Altitude question.

Howdy,

August of last year I took my boat to Lake Tahoe in Ca. (6000' MSL)

All I did was pull the 26p props and put the 24p props on. It ran fine.

You can adjust the idle mixture (air screws) a little if you want. I didn't.


Cheers,


Rick

 

[PiratePast40]

Re: Altitude question.

Depends on which lakes you're planning on. I was at Diamond Lake, Crane Prairie, Lava Lake, and East Lake a few weeks ago. All are 10 mph speed limits so performance isn't going to be a real issue. Diamond does allow higher speeds in the middle of the lake during the afternoon.

The idle mixture screw only affects idle so unless you're trolling, it's a non-issue. Running rich isn't good but a few days shouldn't be catastrophic. Just enjoy the good time.

Catch limits have changed and are lake specific this year. Get a copy of this years regulations and check the lake you're planning on fishing. DNR is out in force for the new invasive species regulations so keep your boat and trailer clean. Sheriffs departments are also out. Passing a safety inspection will get you a "cop repellant" sticker that is recognized in all counties.

Have a ball!