{Stus-List} Engine vibration and RPM fixed

cscheaffer at comcast.net cscheaffer at comcast.net
Sat Jun 20 23:40:13 EDT 2009


I thought you might want to know, I measured the actual RPM of my Universal M4-30 using a hand held dial tachometer and discovered the cockpit tach was reading low.  For years, my engine seemed to enjoy running at 1800 to 2200 RPM and achieved hullspeed easily at those rpms.  Experts were convinced I had the wrong prop and had me worried I was hurting the engine running it at those low RPMs.  The handheld tachometer showed me that the engine was actually turning between 3000 and 3400.  I changed a selector knob on the back of the cockpit tach to "15" and it still doesn't read exact, but reads into the 3000's now.  

Also, I found a fix for the noise and vibration whenever the engine ran.  I bought new mounts but don't have to install them.   It was eliminated by moving the exhaust hose .  The hose had become jambed against a bulkhead where it bends underneath and this caused vibration throughout the boat.  I was able to pull the whole hose and muffler closer toward the engine, by simply undoing clamps and sliding it all forward to provide more slack and a bigger radius bend where it exits the engine box.  It was that way when I bought the boat but has gotten worse.  

Amazing difference.  It's as quiet as a Yanmar on a new boat now.  Launched Friday, tuned the rig today and hope to sail between showers tomorrow. 


1990 C&C 34R
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