My idle speed varies a lot after restart

[SkiDad]

Hi Guys,

My engine has always started easy the 1st time each day and generally starts easy when on the water. Will always re-start 1st turn if I put it into fast idle. But usually will take 2 turns to restart when switching skiers if I just re-start it without fast idle.

When I start it cold its about 1500 for a minute - i wait until 1200 before I put it into reverse. One of the things I noticed is that my idle never seems to be the same RPM when I re-start it later. It will start out between 700-1200 in neutral and anywhere from 700-900 once in gear. If my engine starts at 700 rpm in neutral I wait about 10 seconds and it will creep up 900 and then I can put it into gear fine. This rpm fluctuation will happen every time we switch skiers and there is really only 2 or 3 minutes between off and re-start. I never know if it will be high or low. Obviously no issues if it starts higher like 1200. I don't understand the reason the the varying idles It's something I've always fought on this thing and it seems you really have to mess with the idle speed just to find a spot that is a happy medium for what ever mood the engine is in.

Sometimes when I stop after a long ski run it and go to neutral my rpm will be about 1500 for a minute (this is before I shut it off)

hit the gas and I'm gone and it runs like a champ and any speed... will even idles for an hour with no issues if I'm just cruising at night.

 

[Jiggz]

I've had this problem before and it took more than just one troubleshooting and adjusting to get it a little smoother but not perfect.
1. make sure you are using BUHX NGK plugs.
2. Mine for some reasons seems to run smother with only 1 turn out on the idle mixture screw. Going a little more even an eighth of a turn more makes it sluggish and more smoke and hard starting
3. I ended up replacing the exhaust relief tube due to exhaust leaks making it very hard to idle in the water and yet very smooth at the driveway
4. De-carb the engine by spraying pure seafoam into each cylinder (through the plug hole), lay it overnight and then ran it the next day revving it up with the tie bar up to about 2500 RPM until the soots lightened up. Be careful not to overdo this can damage rings and cylinders due to lightened lubrication.
5. Set the idle (with idle screw) to 900~1000 RPM in neutral resulting to 750~850 RPM idle in gear on water.