Catalina 27 RPMs drop to zero - SailNet Community

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Catalina 27 RPMs drop to zero

I have a Catalina 27 (~1986) with a Universal M18 diesel engine. I went out the other day and while motoring I noticed the tachometer dropped to zero and the battery charging gauge (ammeter?) as well. Boat was moving along as normal though.

A couple days later in the slip I started her up with a some throttle in neutral. After 20 seconds or so, the RPMs and battery charging drops to zero. I have posted a video of this happening. You can hear a change in sound too when it drops.


Any advice on what to look for here?

Thanks
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Re: Catalina 27 RPMs drop to zero

You might do better putting this in the "Gear and maintenance" forum. You have an engine and instruments issue, not a Catalina issue. Although, I'll be interested in any responses you get as I have the exact panel on my C-34.
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Re: Catalina 27 RPMs drop to zero

Yup.
Look for a wire coming off your alternator that runs to the tachometer.
This wire is likely not very well connected - electrically or mechanically.
The alternator provides the engine rpm information to the guage.
Have seen this before on a friends universal diesel.
When the wire is disconnected the tach seems dead. Could also be a short along that wire.
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Re: Catalina 27 RPMs drop to zero

Thanks! I will check wiring and tell you what happens.
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Re: Catalina 27 RPMs drop to zero

I have a similar problem.

A few weeks ago while motoring out of the marina a guest slipped and kicked the throttle lever. The rpms jumped way up b for a second or two until I was able to throttle back. Immediately the tachometer, which had always worked perfectly, dropped down to around 1500 when it should have read 2000. It eventually dropped to about 500 and then would wander back and forth from 500 to 1500. Sometimes it rests on zero. All the time with no change to the actual engine rpms and also no response if I do move the throttle.

The engine is a yanmar 3g. I have looked for a loose wire on the tach and alternator but haven't found anything. The yanmar manual says there is a sensor on the engine, but I can't find it. It seems like it ought to be somewhere near the crankshaft. I think it would look like a temperature or oil pressure sending unit.

Any suggestions? Thanks.
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Re: Catalina 27 RPMs drop to zero

Quote:
Originally Posted by pwilliams55 View Post
Thanks! I will check wiring and tell you what happens.

Check the 12V+ excite wire to the alt. It looks like your alt 12V excite wire is being interrupted which then shuts down the regulator thus shutting down the alternator. The alt sounded "loaded" so I would not assume it is shutting down for over voltage/full..
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Re: Catalina 27 RPMs drop to zero

It could also be a temperamental ignition switch. Had to change mine a couple of years ago for this fault.
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