Vibration

[Piratenorm]

My 1983 30' Mk1 with mid-mounted 10 year old Universal M25-XPB with low hours, with a recently developed harsh vibration just above idle and then again up around 1000 rpms. Bad enough I have had people aboard look my way curiously when I run at that rpm until I nudge the throttle away. I have checked everything I can, the motor mounts are all tight and appear in fine shape (wouldn't it vibrate at every rpm if they were bad?) and she's running fine. Does it in gear and in neutral.
Also I changed my impeller last month and put everything back as I disassembled it and now I have an irregular ticking noise at idle rpms. It does seem centered at the raw water pump. Goes away when rpms increase. Water flow is fine and again, short of disassembling it again or putting in another impeller (my next step) I thought I'd ask here first. This is my 3rd replacement since I bought her and it is the right impeller and it did go back together correctly.
As always, Thanks.

 

[Piratenorm]

BTW, the vibration and the ticking noise started separately, I do not believe they are related. Thanks.

 

[Don S/V ILLusion]

Any pictures of the mounts?

The usual suspect would be loose, compressed or hardening of the rubber dampers.

 

[jimmcgee]

Sounds like mounts. You can't tell if they're bad with a visual inspection unless they're really bad.

There's a couple of threads on here about replacing the stock mounts with Vetus K75's on the C30. It's definitely the way to go and the difference is amazing. Those threads will also give you tips for replacing the mounts without removing the galley (easier with two people).

Since you'll have to unhook the shaft coupler anyway you'll want to look at your cutlass bearing and the condition of your shaft seal.

Replacing the stock packing with a dripless seal will give you a dry bilge and a lot less "boat smell". When you jack the engine you'll be unhooking the hose to the waterlift muffler. Best to replace it with a hump hose if it hasn't already been done.

This is one of those jobs that opens up a lot of "while I'm in here" type projects...

Not sure about the ticking noise.

 

[Stu Jackson]

Also too low an idle. 1,000 is just fine.

 

[jrowan]

I'm not sure if your water pump is like mine, the earlier Oberforfer style, which has a 2 piece shaft & if its not reinstalled correctly it can slip & that might be the cause of your ticking noise. But I believe it wouldn't pump if it was misaligned or disconnected & you would know that real fast. But I had to comment on an idle of 1,000 RPM recommended above. That sounds way too high for any diesel engine, & will just waste fuel at idle & cause unnecessary extra wear & tear on the engine. I would have to research, but I believe the proper idle setting would be around 500 RPM. The idle speed is not causing his rattle. It sounds like bad motor mounts, but could be something as simple as a loose air muffler.

 

[Capt jgw]

The Oberdorfer pump has some play in the mounting bolt holes. The manual says to screw the bolts in finger tight then run the engine for a few seconds to let it align itself, then tighten them up. If it's misaligned, the tang on the pump shaft will slam back and forth in the cam shaft slot and that might make the ticking noise. It will also tear up the pump and shaft in time.