'99 SN WOT: RPM & Speed below normal |
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utahdave
Groupie Joined: April-06-2013 Location: Washington, UT Status: Offline Points: 51 |
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Posted: August-02-2015 at 9:51pm |
Based on the replies I received a few weeks ago, I should be producing higher RPM and top speed with my set-up than I am. Do y'all have any suggestions as to what things I should investigate? Does the ECM have a governor?
More on my boat: 1999 Ski Nautique. Pro Boss GT-40, fuel injected. I had the engine rebuilt in early 2013 by some quality guys. Has 130 hours on it now. Fuel injectors, cap, rotor, throttle body also new at rebuild. The lake where I ski is approximately 2800' above Sea Level near St. George, Utah (Quail Reservoir) Acme 654 propeller. I did a boat test the other day. I was the only person on board, very little gear, no back seat. or back seat backrest. WOT yields 41 mph on both my perfect pass GPS speedo AND on my iPhone GPS speedometer. Max RPM at WOT is 4400. Lake was flat. Engine to drive shaft alignment is correct within 0.003. Driveshaft passes the .003 trueness test on both sides of the strut. Propeller has about 300 hours on it. No knicks. If you take it off the boat and lay it flat, it does not rock when you press on any blade face up or face down. Throttle cable has full travel from idle to butterfly. I took off flame arrestor and visually looked at the position of the butterfly when I moved the driver's throttle arm. Thank you for reading and your input, Dave |
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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Just throwing this out there- have you ever checked the timing? I have never messed with mine but if you were to throw a light on it and watch it while you run it you could see what it's doing. And no on a governor
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21122 |
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Id be curious which heads were put on by your quality engine builder.
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utahdave
Groupie Joined: April-06-2013 Location: Washington, UT Status: Offline Points: 51 |
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Engine Timing:
A mechanic and I set the engine timing according to the instructions (instructions on the ECM, if I recall correctly...removing the SPOUT connector, 2000 rpm, etc). Heads: I will check on which heads are on there. |
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Hollywood
Moderator Group Joined: February-04-2004 Location: Twin Lakes, WI Status: Offline Points: 13512 |
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Did you own it before the rebuild (and why)?
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utahdave
Groupie Joined: April-06-2013 Location: Washington, UT Status: Offline Points: 51 |
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Heads are the GT 40 heads. I confirmed with the engine builder, AND went to the boat today and looked for the 3 bars that (according to the internet) are supposed to be on the GT 40 head. Those bars are there on the front and rear of both the Port and Starboard head. Pic below
I have owned the boat since Summer 2011. I bought it from High Sierra Waterski school. I believe they were the only other owner. When I got the boat, the engine had about 3350 hours on it. I used it until the end of 2012. At that point, the engine had about 3500 hours on it, and the engine was taking longer and longer to pull me out of the water during deep water slalom starts than it did in 2011. I am 6'3, 200 #. At that point, the engine had significantly less "get up and go" at that point than a friend's '97 GT 40 EFI SN that has around 500 hrs on it. Roller cam installed during engine rebuild. In case this factors in: Sadly, I broke the input shaft on the transmission when we pulled the engine for the rebuild. The transmission that is in there now was new, and had been sitting on a dealer shelf for a few years when N3 boatworks bought that dealer out. I got it for a very reasonable price because they were unsure of its status and unable to sell it as brand new. Someone mentioned to me today that some Ford ECMs respond differently if you gun it. When I did my speed test, I slowly accelerate to 17, then slowly to 22, and so on. I did not gun it. Thanks for your help, Dave |
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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But your ECM is programed by Pleasure Carft not Ford,so they would all be the same. I wonder now if either the cam is milder than the original or if the ECM is not compatible with the camshaft if it has been upgraded
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tryathlete
Platinum Member Joined: April-19-2013 Location: Lake Villa, IL Status: Offline Points: 1797 |
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Seems like a few questions are in need of answers first.
1) what was top speed before overhaul? 2) did you verify with gps (iPhone apps work for me)? 3) have you done anything recently to the boat before noticing a drop in speed? 4) assume both speedos read the same? |
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2008 MasterCraft 197TT
1996 Nautique Super Sport 1988 Waterlogged Supra Mariah |
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