RWC water pump did not prime?

[am_dew]

Volvo AQ130C 4 cylinder, raw water cooled I/O with VP 270 outdrive<br /><br />Had a strange thing happen the other day. Bear with me on this...I'll try to keep it as short as I can. <br /><br />In anticipation of a fishing trip and since I had not run the boat for about a month, I decided to start her up in the driveway the day before the trip. Each time I run the boat in the driveway, I unhook the hose that attaches to the incoming side of the mechanical, engine mounted water pump and supply water at low pressure from a garden hose using a custom hose attachment I made. No problems doing that and everything was fine. The next day, I launched and started the engine and everything was fine. Since this is a 5 mph max lake, I very slowly cruised for no more than one minute to get further out in the lake where we would start trolling. Max rpm during this time was 1000 rpm. I happened to look at my temp gauge and it was right up to the red section (the temp gauge only has a large green and a small red secion; no numeric intervals), so I shut the engine off immediately. I checked the hose that feeds the water pump and did a general engine check and all looked fine. I guessed that because the engine had not been revved over 1000 rpm, the water pump had not "primed" itself and just needed a little "kick start". So, I started the engine back up and ran the RPM up slowly while observing the temp. gauge. Sure enough, as soon as the RPMs went over about 1500, the temp started quickly falling and did not take long to lower to what is typical. I backed off the throttle to abut 800 rpm and the temp stayed normal and it was fine for the rest of the day. <br /><br />One thing of note that may or may not have contributed to this. The lake is 7900' elevation. I have to wonder if perhaps the lack of oxygen that is at that altitude contributed to the water pump not being able to prime itself?<br /><br />I will be checking the impeller that is for sure since it probably ran dry during that one minute when it did not seem to be drawing water. It's due for replacement anyways, so I will replace it regardless what it looks like. I don't think I need to be overly concerned about overheat damage since the engine was idling and the small amount of time it probably was in the hot range...I figure it took at least 30 seconds before the temp raised above normal, so that only leaves another 30 seconds it ran while very hot. <br /><br />Any comments?

 

[Don S]

Re: RWC water pump did not prime?

Just an FYI, you do not have a raw water cooled 130, it also has a closed cooling system in it also (the antifreeze part).<br /><br />If you have any air leaks in the cooling system on the suction side of the raw water pump, it will not draw water up. A common place is the hose connection on the drive just below the ujoint bellows where the S shaped hose attaches.<br />That fitting corrodes away and allows the pump to suck air and not water.

 

[am_dew]

Re: RWC water pump did not prime?

Thanks Don. Not to argue, but I assure you it is fully raw water cooled...no antifreeze in it anywhere.<br /><br />I just went out and inspected the area you mentioned and all looks fine. I really think the problem was due to some sort of air pressure issue from the raw water pump on down, perhaps due to the high elevation I was at.