09/04/2007 11:06:01 PM
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RCPILOT
Admiral
Posts: 274
Joined: 07/11/2007
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Was stretching the legs of our 37 Carl Craft, had her up on plane,
when the port throttle linkage barrel let go. She dove hard to
port, I throttled starboard throttle back to idle. Went into the
engine compartment to check it out, both transmissions still in
drive (1st mate at helm) and heard a knocking noise from port side
with rotation of drive line. In neutral, it doesn't make a sound,
so eliminates the engine. Don't know if the knocking was from the
trans or the new v-drive (which was replace 4yrs ago). Any idea's
gentlemen ?
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09/05/2007 09:39:02 AM
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TheJudge
Admiral
Posts: 282
Joined: 05/01/2006
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We have discussed this problem several times in the past beginning, I think, when mine was making the same noise. I was jumping to the worst possible conclusions of transmission rebuild or V-drive replacement when OHB came to the rescue. There are damper plates in the transmission that are loose and can cause this noise at idle speed in forward or reverse. It is basically harmless but will make you think the thing is going to tear up. Mine acts up on and off I guess depending on the rotation of those plates. Just to be safe I would at least change the transmission fluid and also pull the short driveshaft between the transmission and V-drive to see if it could also be the u-joints. You can get a machine shop to replace those for about $100 per shaft. They are truck U-joints. But if it is the damper plates just learn to live with the racket.
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The Judge Rules
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09/05/2007 06:09:56 PM
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RCPILOT
Admiral
Posts: 274
Joined: 07/11/2007
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I can almost feel this knocking on the bridge at the right RPM.
Are we talking the same knocking noise? The transmissions
are a pair of Velvet-Drives.
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09/06/2007 08:55:48 AM
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TheJudge
Admiral
Posts: 282
Joined: 05/01/2006
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I certainly would not swear to your problem without being onboard. But I need to correct one thing you said. Your transmissions are NOT a pair of V-drives. Your transmissions are connected to the rear of your engines. They are not large like a car because there are no gears to shift. Just simple forward and reverse. Then you have a short shaft with a U-joint on each end that connects the transmission to the V-drives. All a V-drive does is take the motion of that short shaft and turn it in a V so that it can drive the prop shaft out the rear of the boat. There is nothing in the V-drive that shifts any gears. They are fixed in position like a differential and will turn in either direction depending on the input from your transmission via the short shaft. I still say to pull the short shaft and inspect the U-joints and while you have it out crank the engine and put it in gear since it is not connected to anything and see if you still have the noise. By the way, it will not be nearly as pronounced without the resistance of the drive line.
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The Judge Rules
Edited: 09/06/2007 at 08:58:03 AM by TheJudge
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09/06/2007 08:03:53 PM
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enginetamer
Member
Posts: 87
Joined: 02/14/2007
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This seemed to happen so quickly that one wonders if he has got a prop fouled up in net or trap?
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lookin' for adventure and the next wild engine!
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09/06/2007 08:07:52 PM
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enginetamer
Member
Posts: 87
Joined: 02/14/2007
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The other thing that jst occurred to me is when you said you just had parts replaced. I wonder if the shaft coupling is really out of alignment ( faces not exactly parallel, as it can have a clunking effect. Next act in that scenario is a broken shaft where it is fastened inside the rear couupling half. Nottrying to scare, but suggesting you have the mechanic come back for follow-up on his work.
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lookin' for adventure and the next wild engine!
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09/06/2007 08:29:18 PM
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RCPILOT
Admiral
Posts: 274
Joined: 07/11/2007
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Originally posted by: RCPILOT I can almost feel
this knocking on the bridge at the right RPM. Are we talking
the same knocking noise? The transmissions are a pair of
Velvet-Drives.
Judge, I'm not sure where you see I said that my transmission's
were "V-drives", but a "Velvet Drive" is a type of Transmission, my
"V-drives" , if I'm not mistaken, are Casale Mfg . I
think I'll try a stethescope to the trans and to the
v-drive while in gear and if that doesn't work, I'll
remove the shaft. Enginetamer, good idea's, I'll take a look at
them. Thanks for the tips.
Edited: 09/06/2007 at 08:35:35 PM by RCPILOT
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09/07/2007 08:34:52 AM
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TheJudge
Admiral
Posts: 282
Joined: 05/01/2006
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My apologies for misreading your prior post. The stethascope is a good idea. I bought one with a probe at Auto Zone and used it with great success.
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The Judge Rules
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09/08/2007 07:53:02 PM
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LongJohn
Member
Posts: 123
Joined: 11/13/2004
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A mangled or unbalenced prop is a good source of driveline knock.
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Harbor Master 47
Watts Bar Lake - TN River
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09/16/2007 11:18:54 PM
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RCPILOT
Admiral
Posts: 274
Joined: 07/11/2007
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Turns out, the knock had something to do with Ignition and fuel.
Talking with someone who owns a large marine transmission
company, (who I promised to leave nameless) told me about some type
of resonance from the engine being out of tune. We were having a
couple of cocktails when he told me of this, I thought he was nuts.
The next day, as I was sweating in the bilge over the running port
engine, I brushed the plug wires and got toasted. Looking at the
plug wires on the HEI converted distributor, I noticed they were
all miss matched. The starboard engine's plugs and wires are about
6 mos. old, so I replaced the port plugs/wires/cap. Cleared the
knock up. I plan on rebuilding the carburetors when I have the boat
hauled out in two weeks.
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09/17/2007 05:44:39 AM
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BananaTom
Admiral
Posts: 968
Joined: 12/05/2006
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Congratulations, spark plug wires are cheeper than a transmission>j
Just as the Judge stated above - We always jump to the worst conclusions.
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Banana Tom
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