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dap
RO# 11327
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 Posted - Aug 06 2012 : 17:21:10
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How much,if any vibration should be felt while underway.Twin inboard 454cu in.I detect some vibration around 1600rpm with both engines running.But how do you gauge it.I ran the port up to 1600 and 1700 with the starboard in neutral and felt nothing,did the same with starboard, port in neutral same results.Both engaged feel some.What to look for.Cutlass bearings,engine mounts,props are good.Engines run smooth.
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jtybt15
RO# 3300
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Posted - Aug 06 2012 : 18:35:37
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Harmonic vibrations? Try running one engine at set RPM and adjust the other engine RPM to see if there's a compatible RPM
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Charlie
There is much to be said, in a world like ours, for taking the world as you find it and fishing with a worm.-Bliss Perry, 1904
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Homeport: Ca
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JimPend
RO# 5022
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Posted - Aug 06 2012 : 18:57:23
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All boats will vibrate even if all is balanced, bearing are good, shaft is good too. It's called prop beat and the boat will respond if it gets in harmonic with it, don't run that RPM.
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| Jim P. |
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Homeport: Port Clinton, OH
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Billylll
RO# 24494
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Posted - Aug 06 2012 : 23:02:58
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Unless you have an electronic engine sync system just being off 100 to 250 rpms can cause this harmonic oscillation/ vibration. Follow Charlies instructions. If it isn't bad I suggest what Jim said just don't run at that rpm for any length of time. Before I installed my Morse Teleflex KE-6 engine sync on my Morse KE-4 electronic shifters I would notice this once the electronic sync was installed I haven't had the problem unless I drop the sync out if the rpms are close but not close enough.
Bill
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WirelessOne,
40 Mainship
Sedan Bridge
Little Egg, N.J. |
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Homeport: Tuckerton, N.J.
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Sandy
RO# 1159
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Posted - Aug 07 2012 : 11:06:34
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I use the Sturdy Corp's Accusync active synchronizer and love it to minimize exhaust harmonic vibration, but some engine , muffler design and exhausr hose lengths just set up more harmonics than others. I changed out brand new Centek Vernatone single stage mufflers for 2 stage mufflers and harmonincs were hugely improved though not completely eliminated.
You might have your props scanned and engine/shaft alignment ( to max. .003 gap at loosened propshaft couplers) checked in-water, make sure all U/W anodes are tight and not out of position (like grinding on the strut or loose/vibrating on rudders or tabs) , check play at the cutlass bearings and rudder ports & strut fasteners.
On some hulls there is a way to really greatly reduce the "prop beat" Jim Pend mentions above, by adding a small wedge and air induction holes ahead of the props to create a minute insulating layer of air on the hull above the prop wash , but it's best suited to installation on single engine downeast hulls. A whole lot of what people usually chalk up to just "diesel vibration " underway is really prop beat. More blades can also reduce that effect in a different way.
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| Sandy |
Edited by - Sandy on Aug 07 2012 11:07:07 |
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Homeport: The Vineyard
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Vibration
