My engine idles high...... Why?

I have an '87 Tristar with a 351. Floats are adjusted correctly. Idle screw is set to idle at 1000. Air mixture screws are correct. When I first start the boat, it idles at 1000. If I run it for a bit at 35+ mph, then stop, it idles at 1800 in neutral. If I turn it off and re-start it, it drops to about 1400.
If I start it up and run it at wakeboarding speed, it isn't as pronounced. The idle goes up to about 12 or 13 hundred.
I was thinking air leak, so I replaced the base gaskets on the carb and spacer. No difference.
Anybody have any idea's????

cable not adjusted properly?

No, the cable is fine..... in fact, once it's idling at 1800, I can unscrew the throttle adjust screw all the way out and it stays at 1800. If I do that, though, I would have to adjust it back down the next time I start it, otherwise the motor won't stay running. So then I adjust it to 1000 again, run it, and it goes up. Weird.

I have a the same problem to a lesser degree. If I rev up to 3k or so mine will idle up to 1100. It normally idles about 600. When it is that high it goes into gear very hard. When I turn it off for a few seconds it will return to normal. It is a very strange thing. Any help would be appreciated.

hmm, i dont know alot about your motor, but a thought just occured to me. If it has a butterfly valve to control the air intake amount, it could possibly be stuck, allowing the motor to bring in as much air as it wants on idle and spinning it up.

When I look down into the carb, the valves seem the same either way.

Perhaps timing needs adjustment? Maybe the chain has stretched a bit.

I'd gie it a regular tune up. You may have a bad vacuum advance. Also, I'd guess' with that year you have a distributer? If so, make sure the spindle is tight.

How would I check the vacuum advance? I'm not sure what that is. Is there a test that would prove/disprove that?

IIRC, on a Ford there's a vacuum tube connected to the distributer. Take it out and plug it with a golf tee. Run your engine around and it should get more ragged the faster you run it.

If you do it in the drive way, you should feel some suction in the tube. ( placing your thumb over it ).

Do you have the Chilton's manual for the motor/boat? They usually describe most of the tune up tests/specs.

First off all adjustments other than choke are done with the engine hot. Now when it is acting up grab the throttle plates and push them against the stop, did the idle go down? You can spray the linkage with a lubricant to help it move smoothly. Timing can cause this problem also, but it is going to be harder to check, as you will need a timing light. After checking the vacuum advance, check the base idle timing and make a note of it. Then with the engine acting up check it again. If the weights inside stick it can cause a high idle, that will go away if you shut the motor down, hence resetting the weights.

New points and condenser can never hurt that motor if you do need to go in and clean the distributor weights. Be careful not to stretch the springs on the weights. Usually there is a screw right on top of the distributer or a C-clip.

If you still need help let us know which carb it has and what kind of distributer (points or?). Good luck!

what's best place for manuals online?

http://www.skidim.com
They should have one for your boat.

Chilton's also has some online manuals.

I'd suggesta google search like: 1987 Tristar manuals, online.

Also, for just the motor: www.cybrrpartspro.com

Good luck.

(Message edited by leggester on July 08, 2003)

If you have a 4 barrell carb. be sure to make sure the rear secondary butterflys are shut completly. I have seen them stuck open just a little bit and cause increased idle. Neal

This isn't going to help solve your problem, but when you do get it fixed, you idle should only be 600-700 out of gear, not 1000. You are tearing your transmission apart slowly if you are dropping into gear at 1000 RPMs.