Boats For Sale:
High RPM |
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MrMcD 
Grand Poobah 
Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3750 |
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 Topic: High RPMPosted: September-01-2019 at 4:22pm |
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Glad you got it fixed. Put one it down as a win.
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Ken W
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Joined: March-04-2019 Location: Michigan Status: Offline Points: 12 |
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Posted: August-31-2019 at 11:31pm |
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Thanks to all for the input. I cleaned the connections on the tach and she's back to normal. The engine sound didn't appear to be running any different when it was reading high RPM.
Bad tach is all it was. Man I feel stupid! |
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MourningWood
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Joined: June-13-2014 Location: NorCal Status: Offline Points: 917 |
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Posted: August-23-2019 at 2:04pm |
I think if the boat was truly turning 4200 rpm while moving at 25 mph, you would definitely notice that. It should have been going @ 40-ish. Doubt that could have anything to do with throttle cable, Seems it would have more to do with 'slippage' or a mechanical problem in the driveline, i.e. weeds, prop spun on shaft, coupler, or trans itself. |
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1964 Dunphy X-55 "One 'N Dun"
'I measured twice, cut three times, and it's still too short!" |
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quinner
Grand Poobah
Joined: October-12-2005 Location: Unknown Status: Offline Points: 5828 |
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Posted: August-21-2019 at 12:30pm |
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On the Excal the Shroud that covers the flame arrestor can interfere with your throttle cable if you also have Perfect Pass, Not certain the same can happen with the Apex.
To rule this out just remove the shroud and see if the issue goes away, also check your throttle cable path to ensure nothing is pushing against it or that it runs neatly along it's path. My excal had this issue and I trimmed the shroud a bit and problem solved. |
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MrMcD
Grand Poobah
Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3750 |
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Posted: August-21-2019 at 12:18am |
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I guess first, is your tach correct? 4,200 RPM is very noisy so I guess you would know if it really is turning that fast.
The only thing I can think of that would allow 4,200 RPM @ 25 MPH would be the prop or tranny slipping. Prop can slip if you sheared a keyway. Properly lapped in this would never happen. Tranny can fail allowing slipage. Check your tranny fluid first, maybe it is just a little low. Your new idle issue is odd to show up with all these other issues. The tranny or Prop would not affect the idle speed at all. The engine should idle the same even if you disconnected the transmission from the engine. Keep us posted on your finds. Mark |
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Ken W
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Joined: March-04-2019 Location: Michigan Status: Offline Points: 12 |
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Posted: August-20-2019 at 11:21pm |
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I have a '97 196 with a chevy 350 5.7 EFI TBI. It has run flawlessly this whole summer. Tonight I took her out and she started right up but idled high around 2000 RPM. It came down to around 1500 after running for a few minutes. At around 25 MPH the RPM was 4200! I turned off the boat and let the kids swim and when I restarted it was the same issue. No weeds on the prop.
I did nothing to the boat as far as mods. I ran her 1 week ago and it was fine. Idle was around 700 RPM and at 30 MPH the RPM was roughly 3100. I read the flame arrestor can cause issues but it appears clean. New plugs/wires.....complete tune up last year. Any ideas would be greatly appreciated. Thanks! |
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Ken W wrote: