[C320-list] Grinding noise while motor sailing?

[Scott Thompson]

Or possibly some debris on the prop that fell off when you went to neutral. 



> On Sep 6, 2015, at 10:08 PM, Rick Sulewski <rsulewski at bex.net> wrote:
> 
> JZ, Perhaps if you caught the bow in wave at its lowest point in the trough while the headsail was also pushing the bow lower as the stern "seesawed" at the crest of that wave given that you were also heeling;  you may have ended up with some air between your prop and the hull. The noise could then be attributed to with the prop losing its bite as it was freewheeling and mixing air about the blades at high RPMs before regaining its bite when you pulled back on the throttle (called cavitation when the prop breaks the surface of the water and struggles to regain its bite with all of the air mixing around the prop blades), a rare occasion for a keel displacement hull.
> Rick
> 
> -----Original Message-----
> From: C320-list [mailto:c320-list-bounces at lists.catalina320.com] On Behalf Of JZ
> Sent: Sunday, September 06, 2015 9:35 PM
> To: c320-list at lists.catalina320.com
> Subject: [C320-list] Grinding noise while motor sailing?
> 
> Hello all, Yesterday i was motor sailing with just my headsail up. I was doing about 7.5knots, engine at my usual cruise rpm of about 2800, all of a sudden there was a grinding/rattling type noise and a slight vibration. I immediately slowed the engine to idle and put it in neutral, the noise stopped as i slowed the engine. I then put it back in forward, no problem, gradually increased rpms to 2800 again, and no problem.  I am baffled as to what it might have been? It was fairly rough out, 4-5ft sea’s, we were battling a head current trying to get to our intended destination, hence the motor sailing. We were heeled over approx 15deg. Once we were anchored, i went below and checked the engine/trans area, everything was tight and secure. I checked all the fluids, normal. Trans oil was bang on and nice and clean.
> 
> Anyone ever run into anything like this?
> 
> It is the Yanmar 3gm30f with the Kanzaki trans, approx 2500 hours.
> 
> Thanks!
> 
> Jeff Zinselmeyer
> s/v Escape #934
>