J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Need Help, Advice - Cooling System

I've been fighting with intermittent cooling issues in my 2Q15M for probably six months. I need advice on next steps.

Here's the situation, excuse the length.

It all started about 6 months ago - no water discharge at the dock, temperature alarm. Opened up the water pump and the impeller was cracked at the brass bearing - all parts recovered. Back together, pumped fine, went out to race, ran fine. About 5 minutes after starting to return to marina, no flow.

I've gone thru two paid "mechanics" who have basically done nothing but get her running/pumping again and each time AFTER RACING, no water discharge, engine temp alarm.

So, after taking things into our own hands, the crew has confirmed the impeller is okay and via testing confirmed that we have positive flow from the kingston cock to the thermostat assembly, at each segment. In the process of removing and testing flow we felt like we had a lot of old/bad hoses so everything along the bypass route, including the thermostat has been replaced. Thank goodness for our local oil and gas hose supplier as most of the needed hoses are no longer manufactured by Yanmar.

After all replacements she primed immediately and over two days we ran her two 30-minutes sessions at the dock, in gear at 1800 rpm with good flow. The engine, however never got to the operating temp per manual that would open the thermostat (air temps in the high 40s, water temp 57 degrees) so we don't know anything about flow thru the engine.

So, this Saturday we motored out for our season ending regatta, good flow all the way out (only 15 minutes, max). Had a great day of racing and within 5 minutes of starting back up to return to marina no water flow, engine temp alarm. On me but I did not check for flow immediately on starting, there were main flaking hijinks going on.

So, what next? We'll of course recheck the impeller but ... Restriction in mixing elbow? Issue with exhaust manifold? What??

Help, please.

Frustrated in TX.

Have you checked/change the thermostat?

Oh, yeah. Way past that and problem solved after thermo replacement, descaling block and exchanger, hose replacement, etc. issue isolated to engine draining/not re-priming when significantly healed on starboard tack. Solution? Close the Kingston valve.

Hi, I just replaced the exhaust elbow due to a small leak on my 2gm, raw water cooled. It was original I think on an 82 hull. The elbow and exhaust port on the head were pretty carboned up. I also pulled the thermostat to check flow and discovered it was corroded inop. I also noticed quite a bit of debris in the thermostat housing. So I pulled the housing, cleaned it, pulled the zinc anodes, pulled the thermostat and descaled the cooling system from the input pipe (from the water pump) to the discharge side of the thermostat housing. I plugged the bypass flow to make sure it all went through the cylinder head. While descaling, I pulled the overheat sensor, checked it for operation and verified that the overheat heat sensor worked. By the way, the new sensors are 60 or 65 degree limits. The one I have is white topped listed at 65 degree. So my point is check for flow through the cylinder head. Water in the exhaust might just be bypass flow. Dan, #409

Thanks Navy Dan! We preformed the same descaling from the input pipe to discharge side including the cylinders by recirculating descaler for a bit over 12 hours. It was pretty shocking how much gunk collected in the descaling solution.