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GT 40 not running at full power

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finnz View Drop Down
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    Posted: July-30-2015 at 1:30pm
I have a 1998 nautique with the GT40 it has been running great all summer long. I replaced the battery a couple of weeks ago and it has not run at full power since i.e., it does not seem to plane off as fast as it should and i am only running at about 38 mph at full throttle with just me in the boat (i verified via gps to eliminate a potential speedo issue). Normally at full throttle it is running 45-47mph and takes very little time to get there. I just figured that it was the fuel filter so i replaced it as-well, but still the same issues. Also, only running at a max of 3800 rpms or so. Any thoughts or ideas?
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JoeinNY View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JoeinNY Quote  Post ReplyReply Direct Link To This Post Posted: July-30-2015 at 1:51pm
Use a timing light or test light to check that you are getting spark on all 8 cylinders (alternately and more dangerously unhook one wire at a time to see if it makes a difference. If you are getting spark to all 8 then do a compression test. If all 8 have even compression then get a fuel pressure gauge.   Do these things in that order ...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote finnz Quote  Post ReplyReply Direct Link To This Post Posted: July-30-2015 at 1:57pm
thanks joe
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bri892001 Quote  Post ReplyReply Direct Link To This Post Posted: August-03-2015 at 8:57am
Do you have Perfect Pass on this boat?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote finnz Quote  Post ReplyReply Direct Link To This Post Posted: August-03-2015 at 1:28pm
yep
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Toertel Quote  Post ReplyReply Direct Link To This Post Posted: August-03-2015 at 1:42pm
I changed cap, rotor, plugs and coil last Friday and tooke the FAE off.
Before she would run 43,5 mph
After that, I ran out of lake at 46.6 mph with the ACME 668
All together a 200$ invest and did the trick! (Thanks to Nautique Parts, who sent the coil last minute via overnight and safed the weekend)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bri892001 Quote  Post ReplyReply Direct Link To This Post Posted: August-03-2015 at 7:44pm
Originally posted by finnz finnz wrote:

yep


Make sure the servo motor is taking up all of the slack in the throttle linkage.

It is supposed to do this as part of the initialization when the key is turned to on.

Your recent battery replacement makes me suspect something is amiss electrically. Your PP needs a full 12 volts to initialize properly.

Any slack left in the throttle linkage will give symptoms similar to what you describe. Essentially the throttle will not be opening all the way.
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