Cathunk, gurgle, swoosh

Engine/tranny combo? Prop type/brand?

When I initially put my 3 blade max prop in reverse while moving forward if above 1200 RPM it initially makes those funny noises as you describe. It is normal but it sounds quite dis functional.

We have a Max Prop on our PSC 34 and it too makes that noise when shifting from forward to reverse.

I have a fixed prop on Hush.

What was making the noise, now that we have added our 2 cents worth?

I still haven't been able to figure out what the noise is. I have a fixed prop so I am baffled. Some with the max prop have indicated they too have the noise when the prop is put in reverse.

The noise I hear sounds a lot like air but I don't understand how I can cavitate that much air simply by going into reverse.

I have noticed the same noise (bubbling and gurgling) when shifting into reverse. I our case it seems only to happen when shifting into reverse while slowly coasting forward. I don't hear it when shifting into reverse if the boat is motionless. We too have a Maxprop, but I'm guessing it has more to do with the hull shape and relative location of the propeller, than the prop itself. At any rate it seems harmless (ours has done it for the last 10 years).

Dave
Crealock 37 #151
"Eowyn"

Thanks to everyone for your response. I am going to keep an eye on things hoping the noise is just a quirk of my boat.

Yes! Kenlanu makes exactly the same (and quite disconcerting) noises. The faster you are going forward the more the noise and the greater the "What the bleeep?!?!?!" As others have noted, going into reverse when standing still produces none of these noises so it has be to something to do with turbulance, cavitation, or special gremlins that came with our boats, take your pick.

Fortunately the noise is consistent over the past 6 years and so I assume it is just a normal part of this particular boat. I sure hope I'm right on this one!

Thanks, Jay

SV Kenlanu
Back in Buck's Harbor, Maine---Home!

BirdBrain333 said:

Yes! Kenlanu makes exactly the same (and quite disconcerting) noises. The faster you are going forward the more the noise and the greater the "What the bleeep?!?!?!" As others have noted, going into reverse when standing still produces none of these noises so it has be to something to do with turbulance, cavitation, or special gremlins that came with our boats, take your pick.

Click to expand...

Same thing here. I have removed the cockpit floor to check that the engine (Yanmar 3HM35F) is not moving aft on its soft mounts, but I saw nothing interesting. I thought about going over the side to see what was going on in the water, but it seemed likely to be one of those, "Honey, hold my beer and watch this." ideas.

I have a two blade fixed prop.

Bill Murdoch
1988 PSC 34
Irish Eyes

Welcome home,Jay.

Our 34 has always made the same described noise when reversing when you still have a little forward momentum. Thought it was a Max Prop thing but sounds like it will do it with any prop. My guess is the disturbed water from the forward momentum causes a little prop cavitation. No worries!

John S
PSC 34 #201
Norstar