1997 won't stay running when bringing the throttle back to neutral after starting

[WLskinautique]

1997 Ski Nautique

The engine turns over and will start if throttle is juiced a little bit. Once I pull back the throttle to idle, the boat dies. Kill switch circuit was just replaced.

Any other suggestions or ideas on the issue? Please reply and I'll answer any questions!

Thanks everyone!

[mzimmer75]

Carb 351 or GT-40?

[WLskinautique]

Carb 351

[mzimmer75]

Does it run ok at skiing speed? Just an idle problem? No recent repairs other than kill switch? If the kill switch was the problem, the engine wouldn’t run at all. Does the idle problem happen with both a hot or cold engine, or only one operating temperature extreme?

[SilentSeven]

I'd start by checking the carb linkages and throttle return stops. Does the boat have a Perfect Pass installed - the PP servo system will be part of the throttle linkage...

Do you know when was the last time the carb was rebuilt?

[Jonny Quest]

Sounds like a simple adjustment of the curb idle screw and / or low-speed circuit screws.

This is what I would do if it was my engine:

1. Disconnect linkage from throttle cable at carb (most likely this is the red cable). This should be a brass colored ball-and-socket type coupling that is spring-loaded.
2. GENTLY turn idle mixture screws in (clockwise) until they barely bottom out. Count the number of turns from the existing position to gently bottomed-out. Write down the current starting point for each mixture screw. Remember, there are 2 idle mixture screws, so you will do this for both screws.
3. Open idle mixture screws to 2 full turns out (counter-clockwise) from gently bottomed-out
4. Start engine -- use your hand on the carb throttle linkage to keep the engine running if it wants to die.
5. Warm-up engine to operating temperature
6. Turn curb idle screw so that engine maintains 650 to 750 RPMs -- in (clockwise) will increase the RPMs
7. SLOWLY (1/8 increments) turn idle screw in until the RPMs start to drop. Back out 1/4 turn. Repeat for the other idle screw.
8. Re-set the curb idle to 650 to 750 RPMs

If the engine refuses to idle at 2 full turns out, you can repeat the procedure but start at 1 full turn out. If that doesn't work, then try 3 full turns out. If the engine still doesn't idle well, you might need to disassemble the carb for a rebuild and cleaning.

JQ

[Skidave]

Sounds like a simple adjustment of the curb idle screw and / or low-speed circuit screws.

This is what I would do if it was my engine:

1. Disconnect linkage from throttle cable at carb (most likely this is the red cable). This should be a brass colored ball-and-socket type coupling that is spring-loaded.
2. GENTLY turn idle mixture screws in (clockwise) until they barely bottom out. Count the number of turns from the existing position to gently bottomed-out. Write down the current starting point for each mixture screw. Remember, there are 2 idle mixture screws, so you will do this for both screws.
3. Open idle mixture screws to 2 full turns out (counter-clockwise) from gently bottomed-out
4. Start engine -- use your hand on the carb throttle linkage to keep the engine running if it wants to die.
5. Warm-up engine to operating temperature
6. Turn curb idle screw so that engine maintains 650 to 750 RPMs -- in (clockwise) will increase the RPMs
7. SLOWLY (1/8 increments) turn idle screw in until the RPMs start to drop. Back out 1/4 turn. Repeat for the other idle screw.
8. Re-set the curb idle to 650 to 750 RPMs

If the engine refuses to idle at 2 full turns out, you can repeat the procedure but start at 1 full turn out. If that doesn't work, then try 3 full turns out. If the engine still doesn't idle well, you might need to disassemble the carb for a rebuild and cleaning.

JQ

Great write up.

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