Compression Gauge

[captaingary]

Does anyone know where to get a compression gauge at a reasonable cost that will work on the Universal Diesel?

[Ron Hill]

Gary : Go by a NAPA store and see what they can get for you.  They usually have a varity of ($$) instruments.  

[David Sanner]

One thing you may already know is that you can test the compression through the glow plug socket.   This saves the hassle of removing the injectors.  You just need the right adaptor...

Stating the obvious...
When testing you want to have the engine stop lever pulled (to stop all fuel flow to the engine) as well as the cooling water cut off so you don't fill your muffler with sea water.

[Ron Hill]

Guys : Scanner mentioned it, but shut off the raw water thru hull or you'll really screw up your engine if the muffler fills and back flows into the engine!!!!!!!!!!!!!
In fact anytime you are turning the engine over and not intending to have it start - shut off that thru hull.  If you forget and start the engine with that thru hull off you have plenty of time to go down and turn it on - after you don't hear that no water coming out of the exhaust.  I'll guess that it takes about 5-8 minutes for the engine to start to overheat with no cooling water.  

[John Langford]

But how long does it take for the impeller to start falling apart? I started the motor at 5am the other day (tide waits for no man!) and forgot that the thru-hull was closed. The engine ran for a couple of minutes before I noticed. The impeller did the job for the whole cruise (three weeks) but I haven't had the courage to look at it yet.

Cheers,
John

[Ray & Sandy Erps]

I suspect that the folks who know how long it takes to destroy an impellor don't want to admit it.  The good news is that if you forget to open the thru hull valve, there is a little residule water left in the impellor that may keep it cool and lubricated for a little while.  As far as spinning the engine a little while for compression tests, I wouldn't think that would harm the impellor.

[Ken Juul]

Might want to give your local "AutoZone" a call.  They have a good tool loaner program.  They don't list the tester on their web page, but individual stores carry a variety of tools not listed.  Unless you want to add to your tool chest, borrowing a seldom used tool makes alot of sense.

[SteveLyle]

OK, I admit it, I fried an impeller earlier this year when I started up the engine without opening the through-hull.

As it was not a planned activity, I neglected to time the time  involved.  But it wasn't more than a few minutes.  Maybe 5.

My practice is to remove the impeller whenever I need to run the engine with no cooling water, the most typical example is in the fall.  I always wait, for some reason, to change the oil until after the boat's out of the water.  So I pull the impeller, run the engine to warm it up so the oil will flow (keep an eye on the temp gauge, it can take 20-30 minutes to get to full operating temperature even without any seawater circulating), change the oil, and leave the impeller out for the winter (stored in a baggy with some silicone spray) on top of the air cleaner so I don't forget it in the spring.