'06 Yamaha F15 4 Stroke

[jdun1]

I tried to post earlier on this issue but I don't think it worked, if this ends up being a duplicate I apologize.

Here's my problem. I have a 2006 15' G3 v-hull with a 2006 15 hp four stroke motor. What a joy, starts beautifully, runs great, quiet, love it! Until we relocated from an elevation of 200' above sea level to 4,800' above sea level!

By GPS I could plane quickly and top out at just about 28 mph at sea level, it was great. Strictly used for fishing and duck hunting. Unfortunately, now I'm lucky if I'm doing 5 mph, obviously no where near planing. Basically the motor is useless as I don't need another trolling motor. I know its the lack of oxygen because it starts like a charm and actually runs great, very smooth, just zero rpms/top end.

I contacted yamaha in Atlanta, and three yamaha dealerships. All said the same thing, "nothing you can do". They will not re-jet when I asked about it, I guess a liability issue if the motor goes back down to sea level and burns up! I did drop the pitch on the prop down to a 9 versus the 11 that came on the motor, did not change a thing. I have been in the archives and believe the only thing I can do is to re-jet. Which I'm sure I could if I could find more info.

My question is this, is there a manual out there that I could use for a 2006 motor (same as 2004?), or any other resource where I could find out what size jets would get this somewhere close to its original performance? I understand it will never be the same, but 5 mph! Does anyone know of a good shop I could work with here in Salt Lake City, Robertson's Marine was not much help. I spent every minute I could in the boat prior to re-locating, love to be on the water but it just isn't worth it now. Is there anything that I can do?

The dealer said I could trade it in and they would give me $1,800 toward a new 20 hp model, but what would that accomplish, another three or four mph? Do they just not use outboards in the Rockies?

I appreciate any recommendations on where I can get more information on re-jetting.


Thanks.

 

[crashnburn63]

Re: '06 Yamaha F15 4 Stroke

I'm a boating newbie, but I've got a lot of experience with airplanes, where you are always dealing with the altitude issue. The mixture on a carburated engine has to be leaned out with altitude to maintain the same 15:1 (or so) air/fuel mix. But it sounds like to me that since the engine idles well, the idle jet (which supplies gas when the throttle plate is closed) isn't the issue.

On piston-engine aircraft there is always a mixture adjustment knob or lever, and you lean the engine as you climb, but usually not until 4 or 5000 feet. Salt Lake really isn't that high to account for such a drastic loss of power. I'd have to dig around to find a table, but I would expect something in the 10 or 20% range. If it was running over-rich, I would expect to see a lot of black smoke and/or unburned fuel coming out.

To further cap it out, the speed of a boat only goes up with the square of the power (a rough rule of thumb for non-planing conditions, meaning double your power and speed only increases by 50%) so you may be even worse off power wise than you think.

Could something else have happened in the move? Maybe a linkage is jammed, for instance?

My less than $.02,

-dm

 

[CatTwentyTwo]

Re: '06 Yamaha F15 4 Stroke

The factory and the dealers may be limited by emission regulations when it comes to re-jetting the carburetor. 15 hp sounds kind of small for that hull. What is the maximum hp that the hull is rated for?

 

[jdun1]

Re: '06 Yamaha F15 4 Stroke

dm - thanks for the response, it's obvious you have experience with this stuff. Honestly, the motor runs oerfect, other than the loss of power, in fact the boat was shipped out, covered, and is in operfect shape. It starts right up idles great, but when you go to wide open throttle it's as if it's only open a third of the way, no sputtering, stalling or anything. I really think it's starved for oxygen. There is no black smoke at all. It runs very smooth, unfortunately just no power. And without that no plane. I had the cowl off, checked all the wiring, plugs, everything is clean and in place, also took the fuel filter off and that was clean as a whistle. I did use gas stabilizer over the winter but again it runs very smooth. I am surprised that with all the discussion on prop pitch that that did not make any difference. Should dropping from an 11 to a 9 made a noticable difference even with limited hp?

 

[jdun1]

Re: '06 Yamaha F15 4 Stroke

Seaman -

The factory did mention the EPA so I can understand why they would want to stay away from the jetting issue.

The boat is rated for a 25 mph motor. I was considering the 20 hp, but if that motor runs similar in this altitude there is no way it will be much help. I certainly can't justify the dollars to go to say a 30 - 40 hp if it's still going to be severly under powered at this altitude. It still boggles my mind that someone would spend $3,000 on a 15 hp motor in this area to get less than 10 mph out of it. The factory told me that they do absolutely nothing differently on the motors they ship to the Rocky Mountain States. Hard to believe. hey must sell many. There are lots of high powered ski boats here, many in-boards. Possibly those are the only boats that can be modified to run well at this altitude? Thanks.

 

[GEPA]

Re: '06 Yamaha F15 4 Stroke

I have a F15 bought in 2007 and use it at sea level and at over 6000 ft regularly and see no difference on performance at either level. I have it on a G3 1548 so about the same boat as you. You may have a fuel supply problem. Try running some carb cleaner through the motor or ask you dealer to look at the carb.

I am in Canada and last winter did not even drain the fuel....after 4 months in the garage it started first pull on the water in the spring.

This winter I have drained the fuel so we will see what next spring brings.

 

[GEPA]

Re: '06 Yamaha F15 4 Stroke

I have a question for others with F15's. Has anyone replaced the carb with the F20 carb to get the extra 5 hp. I have reviewed the parts manuals and the only difference I can see btwn the F15 and F20 is the jet/needle etc.

When I bought the F15 I did not realize the weight of the F20 was the same or I would have bought the F20 as I was looking for a light wt engine and had selected the 15 HP 2-stroke but was convinced to buy the 4-stroke at the last minute when it was offered at the same price as the 2 stroke.