Outboard motor jetting

I have a jetting question and was wondering if anyone has ever run in to it. I have a 1994 Honda 15hp four stroke, when I put it in the water (Trout Fishing) I normally troll up stream. The motor is doing most of its running at a very low rpm. Saturday I fouled a plug, and I know why. My question is when I re-jet should I just change the pilot jet, and if so would I go smaller or larger.

Well duh Lean jetting don't foul plugs Do you have a shop manual If so, bring it with you to the - Woody's Hooch Trout Fest & Male Bonding Extravaganza [ Ladies Cordially Invited ]- and I will look at the pitures and come up with an expert idear. .

Decisions.... Decisions....

fishdog said:

I have a jetting question and was wondering if anyone has ever run in to it. I have a 1994 Honda 15hp four stroke, when I put it in the water (Trout Fishing) I normally troll up stream. The motor is doing most of its running at a very low rpm. Saturday I fouled a plug, and I know why. My question is when I re-jet should I just change the pilot jet, and if so would I go smaller or larger.

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Rather than rejetting your carb, an easier solution would be to just run a "hotter" plug, or one of the multi-gap platinum series plugs. A hotter plug will reduce fouling and generally perform better as long as you don't run "full-out" for an extended period of time. If you decide you want to run around the lake at speed, just change the plug back to the standard plug - only takes a minute or two.

Rejetting can be tricky at times, especially since you'll need to go "leaner" or smaller in jet size on the main jet. If you go "too lean", you can create "hot spots" and burn valves or pistons when run at higher speeds.

Talk to someone who knows that particular engine set up, since running at extremely low rpm often utilizes both the idle circuits and main jet circuits at engine speeds around 800-1200 rpm. This is known as "transition" speed when you are switching from idle circuits to main jet circuits. Sometimes you can simply adjust the "idle mixture" screw to change this "transition" circuit mixture to lean it out a little more. It really depends on how much modern electronics is incorporated into your engine for controlling the idle speed, etc. If it utilizes an ICS (Idle Control Solenoid), you can't do much with it.

hotter plug might be best solution..
most of the time>> once you start screwin with a carb>> life with that motor is never the same..
good luck there..

Thanks guys.