Transmission slipping or something else? |
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tryathlete
Platinum Member Joined: April-19-2013 Location: Lake Villa, IL Status: Offline Points: 1796 |
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Everything sounds great to me. Erroneous tachometer reading. |
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Crmaverick
Senior Member Joined: July-06-2019 Location: Central MA Status: Offline Points: 190 |
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I set the timing at 10 idle, the distributor manual called for 12 and the PCM manual called for 7 so I set in the middle at 10. I haven’t checked at 4000 yet |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 10637 |
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Well it seems like nobody thinks the transmission is slipping based on a variety of things, but like we talked about, it should slip on takeoff if it's gonna slip. Then again, none of us have been there in person to experience it first hand with you.
Any transmission slip I've heard has been noisy, usually on takeoff, sometimes going around a sharp corner while low on fluid and the pump loses suction, but not in a straight line giving it more gas at 40 plus MPH You could see what the transmission guy(s) think, but I'd rule out everything else first, because you probably wouldn't be too happy yanking it out for an overhaul and then having the same problem after it was reinstalled. I'd try a 0 to top speed blast without stopping at 42 like in your video and see how it acts. I'd also have a timing light with a built in tach hooked up for that blast. You could also disable the secondaries in the closed position and see how it runs, you'll lose some RPM's and speed but not a whole bunch. It won't hurt the engine, it just limits how much air and gas can flow through it, limiting the power. Almost hate to mention it but anytime I've had a tach go wacko, it's been ignition related, that's why I asked about the timing and checking the advance at 4000 RPM. The Delco instructions say it should be about 30 degrees total for that EST distributor. Have you checked the plugs to see what they're telling you? If not I'd check them as soon as you can, before heading out with it again. |
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Crmaverick
Senior Member Joined: July-06-2019 Location: Central MA Status: Offline Points: 190 |
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Sounds good I’ll try all that, the plugs still look new, I guess not enough time to show anything. When I set the timing at the specified rpm in the book, I set it based on my tach reading. Which means if my tach is wrong then I set timing to 10 degrees at the wrong rpm |
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baitkiller
Platinum Member Joined: October-11-2011 Location: SW Florida Status: Offline Points: 1693 |
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$20 on amazon buys a laser tach. Buy one, tape the shaft coupling and tape the crank. Go for a burn.
simple. |
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Jesus was a bare-footer.............
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JoeinNY
Grand Poobah Joined: October-19-2005 Location: United States Status: Offline Points: 5693 |
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Generally agree with above, from the video it doesn't sound anything like a 6500 rpm big block and in my experience that tach couldn't handle either a DUI or an MSD ignition and give reliable results. Get a modern tach so you know what you are working with.
That being said in my experience you can do a few weird things at high speeds with that hull, like pick the ass up out of the water and ventilate the rudder, and eventually the prop - however I don't see that happening with a 431 until the mid 50s. If you are going very fast with more than one person in the boat but the others in the back seat. |
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Crmaverick
Senior Member Joined: July-06-2019 Location: Central MA Status: Offline Points: 190 |
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Good idea I have one on order now and will try it out this weekend. |
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tryathlete
Platinum Member Joined: April-19-2013 Location: Lake Villa, IL Status: Offline Points: 1796 |
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LOL! Speeds approaching mid-50’s and the associated handling characteristics harken to the Jet age when the likes of Yeager and Hoover did our nation’s bidding for us at Edwards AFB.
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 10637 |
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Back to something you asked earlier Mav,
I think I'd order a couple of .110 needle and seat assemblies to get back to original size. They flow quite a bit more than the smaller ones like your .101's that you put in |
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GottaSki
Grand Poobah Joined: April-21-2005 Location: NE CT Status: Offline Points: 3327 |
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Yeah! Hopefully Mav doesn't report back to us " because we were inverted'" |
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
River Rat to Mole |
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FFImarine
Senior Member Joined: June-21-2016 Location: Medina Status: Offline Points: 142 |
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Thank you Keno.... what engine do you have? And what transmission do you have? Besides that the probable cause is low oil pressure not being to able to hold the power at those rpms
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 10637 |
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His engine is a 390 ish HP PCM 454 HO in a 1984 SN with a B/W 10-18
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Crmaverick
Senior Member Joined: July-06-2019 Location: Central MA Status: Offline Points: 190 |
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I ordered some .120 needle and seats. The .110 that came with my rebuild kit I believe are to small based on what I read below https://drive.google.com/file/d/1xAE07AqsjiYXHAJrgv0DtcQzkX3sUpnY/view?usp=drivesdk |
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Crmaverick
Senior Member Joined: July-06-2019 Location: Central MA Status: Offline Points: 190 |
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I had it out today for a test, still reved past 6 but the boat kept pulling and I saw 50, after adjusting the float height on the secondaries it helped make for a smoother transition up top
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