1997 Volvo 3.0 Wants To Run Hot

[MainstreetUSA1]

1997 3.0 Volvo SX<br />Raw Water Cooled<br />Exclusively Fresh Water Use<br />Purchased Used 2.5 Months Ago<br /><br />Was boating last weekend and temp gauge started to approach 220 degrees at cruising speed. I immediately shut down and trolled back to the ramp. Normally engine runs at 175-180<br /><br />When I got back to my shop I pulled the raw water pump and the rubber impeller was toast. Remainng rubber was very brittle I retrieved rubber pieces of vanes from the T-stat housing and from one of the smaller hose fittings before the manifold. I also drained the block and manifold and poked around with a wire to check for any other loose debris (none).<br /><br />Saturday I installed the new raw water impeller and ran on the muffs temp climbed to normal operating temp. I got plenty of exhaust/water exiting the outdrive during warmup and througout the time it was idling. I let it run for about 8-10 mins and shut it down to head to the lake.<br /><br />On the lake anything above 2500 rpms and the temp wants to climb past 200 degrees. I shut down for a minute or two and opened the engine cover. Manifold and exhaust tube were not too hot to hold a bare hand on. Closed it up and idled back to the ramp at maintaing about 175 degrees.<br /><br />Last night I pulled the T-stat (160 degree unit)and it looked like it may have been original. It looked a little crusty and seems to be sticking so I orded a replacement today.<br /><br />I installed a new water circulaton pump 4 weeks ago (the original was begining to leak from the weep holes). Is there anyting else I can troubleshoot? I think that the new T-stat, raw water impeller, and circulation pump will solve the temp problems.<br /><br />Thanks For The Help!

 

[Don S]

Re: 1997 Volvo 3.0 Wants To Run Hot

You can troubleshoot it forever, but till you run it and test your repairs you don't even know if it's fixed or not.<br />The impeller alone was the cause of the overheat.

 

[Lou C]

Re: 1997 Volvo 3.0 Wants To Run Hot

I just replaced the thermostat on my raw water cooled OMC after about 2 seasons in salt water. I tested the old one against a new one in a pot of water, using an automotive radiator thermometer. What I found is that the new one opened sooner, and farther, and after I installed it, it keeps the temp more even overall. Before it was running too cool at idle, and at high speeds it would not overheat, but coming off plane the engine would go from about 160 to 170 or so. Now it stays steady at 160 and the motor warms up like it should. Sounds like you have it about covered. You could try testing the old stat to see if it opened at 160 and closed like it should. If it still heats up it is possible there could be a piece of the old impeller somewhere, you can check the thermo housing when you change the stat, that is one possbile place. Lastly is the riser but if it is not hot after running it is probably OK.<br />PS your temps of 175-180 were a little on the high side even before it overheated, I have found at least with mine (17 year old original raw water cooled motor, at least 4 seasons in salt water, new manifolds last year, new impeller every year) when the cooling system is in top shape it runs right at 160, even after running at 4000 rpm. So the impeller was the cause of the overheat, but something else was causing your temp to be slightly higher than it should be.

 

[MainstreetUSA1]

Re: 1997 Volvo 3.0 Wants To Run Hot

As my post stated I replaced the impeller and it still wanted to run hot under load. Is there anyhing else besides the t-stat that could cause this? My new t-stat should be here in 2 days (on order)<br /><br />Thanks!

 

[Lou C]

Re: 1997 Volvo 3.0 Wants To Run Hot

Ususally what is suspect is the manifold/riser, but in freshwater they are likely to still be good. Worth a look anyway. <br />On a more basic level, you want to check the actual raw water flow with the new impeller if you still have heating problems after the new thermo. With the boat in the water, if you disconnect the hose from the impeller housing to the thermo housing and start the motor (BRIEFLY) while someone holds that hose straight up, it should shoot a stream of water 2-3 inches in the air, at least according to my OMC manual. If not and it the impeller is new, then you have to check for blockages in the hose from the transom to the impeller housing, and there is a chance the water tube that brings water from the lower unit upward could be leaking, or letting air in somewhere and that could reduce the impeller output. Other stuff could be ignition timing off or a leaky head gasket (hope not!) <br />I'd get a Volvo manual as it will make the trouble shooting much easier.