Which one? Honda 9.9 15 or 20?

I am going to buy a used 14’ aluminum boat, to fish at 7000’ altitude lake in California. Which motor will give good performance, and do I need to change out the prop?
thanks in advance.
Roger

You lose horsepower as you go UP due to the density of air being less. The formula is 3% loss for every 1000 ft. above sea level. With the difference getting pretty noticeable above 3000 ft. So, if performance is your main concern, the 20 is the obvious "best" choice. The three outboards you listed are close enough in weight to make that so.

But the price point of the 20 is quite far, in dollars, from the 9hp. If money is anything of an issue, then there's that.

As far as changing the prop, you would need to factor the type of load you'll be moving more than anything else and it's likely the stock Honda prop on any of the three outboards will be adequate for 90% of most tasks asked of it.

Where you will probably need to make a change for altitude will be with the carburetor. Since the air at 7000 ft. is so much less dense than at sea level, you may want to look at having a smaller orificed main jet to keep from running rich all the time. Honda sells different sized jets for these carbs for that very reason.

However, should you bring the boat down the hill to run at sea level, you would definitely want to install the original jet so as not to have the engine running too lean. Lean burn can damage an engine, especially on a hot day.

My approach would be to run it stock at first and see how it goes. If you don't have a big problem with black exhaust or black sooted and fouled plugs then I wouldn't change a thing.

If you do find that she needs to be leaned out a bit but you still want to take her down to fish the bay seaside, I would buy a spare carb and have the proper jet installed. Then a quick swap. and off you go.

Good luck

Thank you for the response. I bought a 12’ Boat, came with an 8 hp 2 stroke Mercury. Got it running, but not happy with it, so back to the Honda decision.
Question- is there any small outboards that don’t use a carb, that would run at 7000’ without adjustments?
Roger

There are some "electric outboards" on the market these days. I think I remember seeing an ad for a 6hp. version not so long ago. But, I imagine that would be at the upper end of the power rating for that type of propulsion.

There are no 10 horse or under fuel injected outboards to my knowledge. 7000' will always necessitate some smaller jetting to compensate for the reduction in oxygen that high up.

Ok, thanks for the info. I’m leaning towards the 15hp because of the power loss at 7k altitude.

If I haven't said it before, Honda does sell smaller orificed main jets for the 15 to operate efficiently at altitude so, that would be a good choice. I believe it weighs about the same as it's 9.9hp stablemate so you get an advantage there too by not taking on additional load as a tradeoff for increased horsepower.

Good info. Thanks
Roger

Hello

i am new to the forum and don’t want to throw this thread off track

i purchased a new BF-15 and put it in the water for the first time in October

the motor overheated pulling away from the ramp

we put it in the shop in October, and it is still in the shop 10 months later

i can get NO HELP from customer service or the local Honda rep

They ended up rebuilding the motor piece by piece and now can’t get it to turn over

10 months later and no motor

i am at the end of my rope.


Does anyone know anyone at Honda with authority to help me

Please start a new thread. You'll get more help that way.

20HP, you will always want more power. Max the HP the boat is rated for and you will never be unhappy.

Tohatsu, Mercury (which is a Tohatsu), and Suzuki all make 9.9 fuel injected motors.

I am looking for lightning strikes mentioning these brands on here.....LOL

Mike

I stand corrected......again.

And, yes Mike, you should be wearing your Faraday suit!!
;>) ;>) :>)

Haha.Did the lightning get you hondadude?
i assume any fuel injected motor will perform at high altitude. I had a ski boat with a Volvo Penta engine, fuel injected, still had to use a power prop at 7000’.

There's no "free lunch" with fuel injection when it comes to operating at altitude. Fuel injected engines are subject to the same horsepower loss at high elevations and use a barometric pressure sensor to detect atmospheric conditions. The fuel delivery will be adjusted down to compensate for oxygen reduction high up. Pretty much the equivalent of re-jetting a carb keep it from running rich at altitude.

There will likely be a small advantage to using fuel injection over carburetion simply due to more precise fuel delivery but I wouldn't expect a huge gain at all.

True. I’m thinking it would be less hassle going from sea level to high altitude, not having to switch carbs. I’m looking into the motors hondadude mentions.

As Jimmy said, the fuel injection will keep the air/fuel mixture where the engine likes it. However, you will have to change props when changing altitudes.

To figure out what prop you need, you will need to connect some sort of tachometer to the motor, to see your full throttle rpm.t is very possible....even at sea level, you may have to change from the standard prop to something else, due to the number of people, equipment, etc in the boat. Once you get the prop set at the elevation that you use it most, then you can work on what you need to change to when you change your elevation.

Mike

Ironically, the electric outboard would suffer NO horsepower loss at altitude but Mike's prop change info would still hold true.

Boating CAN be FUN....when all the work is DONE!