Can the water pump on an 8.1 lose prime?

[highslice]

I was winterizing my boat a couple weeks ago. I put the muffs on the drive and ran the motor for awhile until the temperature got up to operating levels. Shut the motor down and hooked the muffs up to a hose that ends in a 5 gallon bucket full of anti-freeze (no need to discuss if this method is actually right or not, I have done it for 5 years with no issues) and started the motor back up and....nothing. The anti-freeze level didn't change. Usually it's hard for me keep up pouring anti-freeze into the bucket as fast as the water pump draws it out. After checking to see that the belt was turning and the pump hadn't seized. I put the water hose back on the muffs and ran the motor again to see if the temp went above normal levels, which it did not. I puy the anti-freeze hose back on, started the engine and it immediately started drawing anti-freeze out of the bucket at the normal rapid pace.

Not sure what the issue was, but it has never happened to me before. Any guesses?

 

[paulswagelock]

Pump lost prime. When you do this, at a minimum you should have the bucket on the swim platform so there is some head pressure on the antifreeze supply. Ideally you should use a pump in the bucket to pressurize the antifreeze. By design the pump is so low that it is actually below water level so water is forced by pressure to the pump inlet when floating in the water.

 

[Jimmy Buoy]

Here's a tip from a previous Bravo I owner that did his own winterizing for years... me. Your drives don't have internal water pumps. The raw water pump is in the ER and driven by a belt off of your engine. Instead of attaching clumsy muffs on the drive, simply disconnect the water line that feeds the belt driven pump at the transom assembly inside the ER. Use a proper sized fitting to attach your antifreeze line to this raw water line and fire up the engine until the antifreeze comes out the exhaust ports on the drive. Easy.

Just remember to reconnect the raw water line to the transom assembly once done.

 

[AFD]

I was going to suggest this too

 

[highslice]

Thanks to all for replies, I wasn't looking for advice concerning my method as stated in the OP, but appreciate the feedback anyway. The drive is a Bravo III.

Paul, I had the bucket on the swim platform, that is part of what confused/concerned me.

 

[paulswagelock]

Guess it was just an oddity that the system lost prime or had an air pocket. Keep in mind since you have the closed cooling system, there is no need to bring the engine up to temperature. The antifreeze you are drawing in simply comes up through the drive, through the pump, through the cool fuel module, power steering cooler, oil cooler, heat exchanger, then into the manifolds and dumps out the exhaust. The thermostat is on the closed side, not this side.

 

[highslice]

You know I never really thought about that. I have always brought it up to temp to change the oil, but I didn't have time to do that and will in the spring. Force of habit. Thanks!

 

[Lazy Daze]

Paul's right - probably just an air pocket. I might be concerned about the impeller if it ran for a while without water/AF/lubrication, though. If the impeller is more than a few years old I would probably replace it for good measure. If it's new, I'd probably just see how the season (next) goes and watch my temp's.

With your engine, there's nothing wrong with using the bucket method. But you might think about taking one more little step to be totally sure all the water is out of the system. And that's just to either pull the little blue drain plugs or use the air-actuated system - depending on what your motor has. If you use plenty of AF, though, you don't need to worry about it. It just means you'll use more AF than needed, but if it's inconvenient to get to the plugs then a few more gallons of AF is well worth the cost. I know you mentioned you weren't looking for a discussion on "methods" and I hope you understand my comment wasn't centered around that. It was just meant as a tip that can help to make sure there's no water laying somewhere. Some of the areas you have are very small and it wouldn't take much water to cause damage. I've been through this stuff enough times to know that just because a certain way has worked in the past, doesn't mean it will always work. But again, if you're using plenty of AF, then... continue on! :smt001

 

[highslice]

Thanks Dennis. The manual states that the capacity of the raw water cooling system is 5.1 gallons. I always run 7 - 8 gallons through just to be sure. I only let it run for less than a minute before I shut it down because the af level usually goes down very quickly. When it didn't this time, I was grew concerned very quickly. But the impeller only has about 25 hours on it. So I will watch closely as I always do. No worries about the advice on draining. I just didn't want this to be a debate about using muffs vs. pulling water hoses...

I appreciate the replies.

 

[Lazy Daze]

You know, are you sure the manual isn't referring to the "closed" cooling system? Because that sounds about right for the amount of antifreeze in your block. But to be completely honest, I didn't even know there was a spec'd raw water cooling capacity listed by Merc so you very well might be right. It just "seems" like a lot to be held in a few hoses and the heat exchanger, you know? If I'm right, though, that's even better for you as you are DEFINITELY pumping enough AF through the raw water system!

From what you're saying about how long the impeller ran (there still would have been some residual water in there) I'd feel comfortable in just seeing how things go next season.

 

[highslice]

The manual spec the raw water side "for winterization purposes only". I imagine that includes exhaust as well. The cooling system has similar capacity (19 quarts vs. 21 for the raw water side).

I should also mention that the other reason I run the engine up to operating temps is to get the fuel treatment circulated.

Again, thanks for the responses.

 

[somefun]

I work with all sorts of pumps - from small chemical pumps to very large water pumps - on a daily basis at my job. It doesn't take much for most pumps to lose prime, and stopping and re-starting the pump is one of our methods to overcome that. I would imagine you had a small air pocket.