Question about vibration ratcheting noise from prop/shift cable.

[bayliner2252]

Thank you for reading this post discussion as I have been having a real hard time finding out what is the possible cause of my problems. I have a 1997 Bayliner 2252 with a Mercruiser 5.7 MCM with carb that is connected to an Alpha gen 2. I recently had a full tune up on the boat after having the motor rebuilt and on the first test run the boat was good no problems no noises. My current issue is after my second day out on the lake. When I have the boat on trailer and running on hose with muffs I am getting a weird vibration/ratcheting noise. When running the boat in neutral there is no noise that I can detect at all. However I shift the drive into either forward or reverse and I get the normal clunk noise which indicates gear engagement. My problem really comes from if I give the motor any type of acceleration in RPM and let off I get a very faint and subtle vibration/ratcheting noise. I have located that the drive shift cable is vibrating in the mounting plate on the exhaust manifold and this is where the noise is coming from. The prop seems to make the similar noise if I'm out of the boat and watching prop spin while in gear. This noise does this in both fwd and reverse. I have had this boat for 5 years and have had other boats with same drive and never noticed this noise before. Again this noise is only happening when in gear, not in neutral. I have asked multiple mechanics and they say that this is normal but I have a hard time believing this. Now some of the troubleshooting I have done is that I run the boat the exact same way with placing in gear and slight acceleration with no prop on the drive and there is no noise or vibrations at all and my problems are gone. I placed the extra prop that I have on the boat and noise comes back. One mechanic said it might be an overspinning of the prop when not under load. The noise doesnt change if I have the drive turned one way or the other which I would think indicates U joints. Also the drive is always in the complete down position. Again no noise in neutral which makes me believe gimbal bearing is not bad. I am just wondering if the cable is not engaging completely, worn out or has excess play. When in gear the prop spins and accelerates as it is supposed, so no spun prop hub. I am also able to check that gears engage and lock in the directions they are supposed with engine off and drive static shifted. Does anyone have any suggestions.

[admin]

If the noise is gone with the prop off, then i think the mechanic had it right when he said an overspinning of the prop. The engine runs slow at idle and the prop has time to fall backwards and hit the clutch. I usually only hear about this with stainless props though. It sounds like a clicking noise that is not in perfect rhythm. it might be a click, then a little later a click click and then later a click or a click click.

Given its a new or rebuilt engine, i would do a cylinder drop test to make sure they all are doing their job. The engine may seem to run ok, but it may seem imbalanced if one cylinder is not doing 100% of its job.

Tech Support

[bayliner2252]

Thanks for the quick reply. It makes sense to me what you are describing, I just was worried since I have never really heard this type of noise before. As well it just seemed really strange the the noise was coming from the drive shift cable. I was really worried it was jumping in and out of gear. Thanks for your input.