[C320-list] Overheating

[hcreech at comcast.net]

Jack, 
Unless I am reading this wrong you are running your engine at too low a rate of speed. This should not have any bearing on the water pump situation but still way too low. If you continue to run at that low speed you will only create a carbon build-up which is not good. I run mine continuously while crusing a 2800 RPM and only lower speeds while docking. When I took the initial diesel class they stressed that low speeds are very detrimental to diesels. They went on to say you should cruise at 2800-2900 RPM and can run at 3100 RPM for up to an hour without causing any problems. The main point was to "Not Baby" the diesel. Could be another problem, but regardless, if I am reading this right, you need to crank it up. 

Herb Creech 
Cloud Chaser 606 



----- Original Message -----
From: "Jack McDonough" <mcdonough5 at verizon.net> 
To: C320-List at Catalina320.com 
Sent: Monday, August 15, 2011 8:47:20 AM 
Subject: [C320-list] Overheating 

A puzzling, intermittent overheating problem developed a couple of weeks ago with the 3GM30F Yanmar in my 2003 C-320. 

While traveling at low speed from an anchorage to a newly available mooring one morning (maybe 10 - 15 minutes running time), the engine overheat alarm sounded. I managed to pick up the mooring, after which I pulled the raw water intake hose at the seacock and determined that water was, in fact, coming into the system. I then checked to see that the strainer was clear and, finally, took apart the impeller housing and inspected the impeller -- which was newly installed in May and which looked fine. I started the engine again and still got only steam out of the exhaust. A couple of tries later, however, the system once again pumped out water like a champ. 

I made a three-hour passage to another harbor under power the next day and everything was fine -- but the same problem occurred the following day. Again it blew steam -- but the following morning I got a healthy flow of water and headed home. 

Since then, I have again pulled the hose off the intake seacock but, this time, I took my digital wire coat hanger and fed it down through the intake passage to make sure there was nothing flopping around in there. I disconnected the other end of the hose -- at the strainer -- and detemined that there was nothing in the hose. Then I removed the hose between the strainer and the impeller and confirmed that it, too, was clear. 

I have a sense that I'm more likely to be able to pump water if I briefly goose the RPMs up to 2000 or a little more. But I've consulted my diesel guy and he says that shouldn't make any difference. It should pump water regardless. 

That's my story. Any ideas? 

Jack 
#947