It’s suddenly got noisy
QMy 2007 Piper boat has a Beta 35 engine which is regularly serviced. I spend about three months a year touring the canals and rivers and the engine has been very reliable. However, it has now become very noisy when just ticking over and this is very apparent in locks. It ran as smooth as silk on the Trent and it wasn’t noisy, but once back on tickover, the noise returns. Could this be due to excessive vibration? How do I check and re-align the engine mountings, or do they need replacing? MARTIN BRETT, via email
ATONY REPLIES… Does the noise come in or out of gear, or both. With a misaligned engine-shaft you would get the noise in gear but not out of gear; if it’s a broken engine mount you would get the noise out of gear but less so in gear.
On tickover out of gear, try pushing the top of the engine to the left and then to the right. If the noise is reduced it is possibly a broken engine mount. Testing the mounts, unless one is well and truly broken, really requires experience. If a visual inspection shows glossy black slime around a mount, oil or fuel has attacked the rubber so it needs a new mount.
You need to test each mount individually. Get a length of strong metal, possibly a mooring stake, and lay it over the engine beds with the tip under an engine foot (on a Beta probably a length of angle iron that runs the length of the engine), use this as a lever to try to lift the engine off each mount in turn. All should give by the same small amount because of the rubber in the mount. Any that give more are likely to need replacing. Diagnosing from lift requires experience to recognise when it is excessive. Being rubber, the engine mounts will drop over time, but whether this causes engine-shaft misalignment depends upon what type of stern gland and flexible shaft coupling you have. Aquadrive, Pythondrive or long Centaflex couplings allow lots of misalignment so with those it is unlikely to be an issue. Another Centaflex coupling allows a little. A Vetus stern gland and gear will also allow the engine to drop a little without going out of alignment.
I suspect your engine is suspended part way up long studs in the top of the mounts. The top nut is usually self-locking, but the bottom ones can undo themselves unless checked for tightness at least once a year. If one of your lower nuts has come undone it would give you this symptom so check all four lower nuts and tighten the lower nut back up to the top nut.
You can also get this sort of symptom if the nuts and bolts holding the mounts onto the engine bed become loose so check all of those as well. However, you might be best advised to pay an engineer to test the mounts and check engine alignment.
Finally, the driveplate could be failing and an engineer should be able to identify a failing driveplate within seconds.
The rear engine mountings