1997 Sport Nautique with GT40 Engine
I’m having some trouble with a high idle condition. About a month ago i put new plugs in due to a miss, i have learned that particular condition and know the signs. New plugs and it was running smooth again. While changing the plugs I checked the base timing, it was off a little so got that spot on.
I set the idle to 650 and was having a some surging, did some research and found that it was likely the idle air control valve. I replaced it, and for good measure replaced the throttle position sensor, since they were both likely original to the boat so 30 years old.
The boat now idles smoothly at 650, most of the time. A week ago we spent 7 hours pulling the tube with kids from our church youth group. Off and on the boat would not return to 650 at idle, but hover around 1000. The pattern went on all day.
Yesterday we went to the lake and the boat idled smooth at 650 when we put the boat in, then a few minutes later as we idled out of the marina it was at 1000. We spent some time pulling the kids on the wake board and tube, 650 idle each time. Then we ran about 25 or 30 mph for 15 or so minutes back to the marina, and when I pulled back to idle, it was 1000 again. Shut the boat off while backing in the trailer then it idled nicely at 650 again when I loaded it.
Any ideas of where to start looking to correct the random high idle?
I’m having some trouble with a high idle condition. About a month ago i put new plugs in due to a miss, i have learned that particular condition and know the signs. New plugs and it was running smooth again. While changing the plugs I checked the base timing, it was off a little so got that spot on.
I set the idle to 650 and was having a some surging, did some research and found that it was likely the idle air control valve. I replaced it, and for good measure replaced the throttle position sensor, since they were both likely original to the boat so 30 years old.
The boat now idles smoothly at 650, most of the time. A week ago we spent 7 hours pulling the tube with kids from our church youth group. Off and on the boat would not return to 650 at idle, but hover around 1000. The pattern went on all day.
Yesterday we went to the lake and the boat idled smooth at 650 when we put the boat in, then a few minutes later as we idled out of the marina it was at 1000. We spent some time pulling the kids on the wake board and tube, 650 idle each time. Then we ran about 25 or 30 mph for 15 or so minutes back to the marina, and when I pulled back to idle, it was 1000 again. Shut the boat off while backing in the trailer then it idled nicely at 650 again when I loaded it.
Any ideas of where to start looking to correct the random high idle?
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