New Honda BF5A Altitude Question.

[JHo]

I very recently purchased a new Honda BF5A for my 12' port-a-bote. The lakes I go to typically range from 5,000 to 6,500 feet. The dealer insisted that no mods would be required for altitude. Wrong. The motor barely ran first time out. After a spark plug change and a few carb adjustments it now runs but won't plane the boat with just me (140lbs). So I had them order me a prop with less pitch. Do I need to go down 1 size in jets to lean out at these elevations or can I get away with just a prop change? I'm new to the wonderful world of boat ownership so any advice would be greatly appreciated.

 

[steelespike]

Re: New Honda BF5A Altitude Question.

At 5,000+ you definately need a jet change.I assume the dealer would know
what size.You'll need all you can get at that elevatiuon.
I checked some videos and it pops on plane with a 5 hp. one aboard.
Runs right along but really flat, leans toward the outside in a turn.
Should do well once you get it setup. I'm betting you could raise the motor quite a bit.Transom may not be very high.
Running flat my be the bottom flexing perhaps you could add some light support.

 

[JHo]

Re: New Honda BF5A Altitude Question.

Thanks steelespike! I'll look into it!

 

[JHo]

Re: New Honda BF5A Altitude Question.

The stock jet is a #75 0-5,000 feet, #72 is for 5,000 to 8,000 which is what I will be installing as soon as it comes in, and a #70 is for 8,000 to 11,000 feet which I ordered but may never use. I added a Tiny-Tach so once I have the new prop installed and the jet changed I can make sure I have proper WOT rpm range (4,500-5,500). Can't wait to get out on the water and give it a test run!

 

[fishrdan]

Re: New Honda BF5A Altitude Question.

Even with the jet change I wouldn't expect sealevel performance out of your outboard. Engines loose about 3% HP for every 1000' of elevation, so at 6000' you are down almost 20%. A prop change will probably be needed to get you in your WOT range, but do that after running at elevation first and seeing how it performs.

I've run my 7.5HP at 5000-9000' and elevation is a killer on performance. A couple times I jetted it down, which helped, but it was still doggy. The last time I just ran it with sealevel jets at 9000', I was surprised that the performance wasn't that much different than having it leaned out and my 100# kid on board, though I was running it WOT and not idling/trolling. I'm trying to find a lower pitch prop for my outboard as I've been running it with the stock 8P prop at altitude, not good for performance or the outboard.