Air lock during initial launch - water pump

[Cooler]

Trying to find out how common this is. 2nd season my water pump could not draw water during initial season launch. Disconnected hose at the thermostat water input last season. There was a hissing noise of escaping air, and then water started flowing. This year, both engines acted the same way. Disconnected the hose from water input at water pump. Held hose below water line and water strated flowing. Last season I started a test with Globe Run Dry impellers. That was the first time it happened to one engine only. Wondering if this could be a result of Run Dry impellers not having enough suction to start from initial season launch. The vessel is launched from a trailer. The mechanic said the water line from seacock had to run over a stringer before it entered water pump. Opined that left too much uphill draw to get water at water pump location. He recommended new impellers every year. The Run Dry impellers could be at fault, but if I did not have those in, the standard impellers would have been smoked by the time water started running. Is this common? Is it an impeller issue, or a water line issue? Any thoughts on mitigation? Thanks for comments. Hope Viper sees this. er

[km1125]

Wondering how you are winterized? Is antifreeze fed in from underneath via a "plunger", or is it fed in at/near the strainers?

I would think if it's fed in via a plunger, and they shutoff the seacock before removing the plunger then the inlet hose should be full of antifreeze and stay that way until startup. There would only be a small amount of air between the seacock and the sea that would quickly get sucked though the system. There would be plenty of antifreeze to lubricate the pump in the intervening time.

[bud37]

Gee those run dry impellers really do live up to their name and," run dry "....

The standard ones must have worked fine before, they will pull water up quite well.The antifreeze from winterizing is quite slippery so that will lube them at start up each year , in my experience and probably yours.

There are still some folk, MAYBE, that pull their impellers each winter so they don't take a set, maybe these run dry ones take a set more easily and need this sort of treatment.

[Midnightsun]

One thing many overlook when winterizing is using the wrong pink stuff in their engines. The Alcohol based one or the cheapest one if you prefer, will dry out an impeller and cause them to fail well before they should. Not saying this is what you did but as a reminder to others using the cheap stuff for winterizing.

It's like storing your impeller in Vodka all winter, rubber is going to be affected for sure.

[tomschauer]

On most any boat I have owned over the years, if the raw water pump was above the water line, I have had to goose the throttles a bit to like 2000 rpm for a few seconds to pull the water up to the pumps. Only had to do this on initial launch, or after changing impellers, then no problem for the rest of the season.

[Viper]

All good points. I can't comment on the Globe impellers but have read things that and talked to colleagues who've dealt with them which convinced me to stick with the tried and true regular impellers.

There's several things that can contribute to the issue, worn pump, impeller, leak, clog, hose routing, etc. Hans hit my initial thought in that the proper winterizing antifreeze really helps on start up. The product has lubricants that regular plumbing antifreeze doesn't, you can feel it when you rub it between two fingers. If you run antifreeze through the pump at winterizing, your impeller will be lubricated enough to get it through initial start up.

Shouldn't really matter whether the intake hose is full of antifreeze or not over the winter. In fact, if you open your seacock after you finish winterizing which is a must, the intake hose will drain completely leaving only the antifreeze in the pump.

As Tom mentioned, the norm when firing up for the first time in the spring is to chop the throttle a few times, this usually solves the problem, I just wouldn't do it nor is it usually necessary with diesels.

[Cooler]

Engines are not winterized. Stored in warm storage. The support staff at Globe suggested the impellers probably did set while in storage due to their pliable nature. I was thinking they would act just the opposite, due to that pliable nature. So, my Run Dry impeller test is complete. They do seem to pump more water when primed, but the issue with intial launch priming challenge has me going back to standard neoprene impellers. The other issue is the engines run 10 degrees hotter than when I ran neoprene impellers. Will run these for the season, and change out next fall. Had a friend who ran these Run Dry in his go fast boat and loved them. I guess they are not for everybody. Thanks everybody! er

[Midnightsun]

Thanks for the update. Honestly I have never seen any good or maybe I should say revolutionary regarding the run dry units. Not that I have ever tried them however all the reviews I have read were mostly negative so I never bothered trying in the past.

[Viper]

Source of the post......Will run these for the season, and change out next fall.....

There's no sense in replacing impellers in the Fall on a vessel that is laid up for the winter. You'll be starting off with new impellers that have already taken a set for almost 6 months before you use them for the first time. Change them first thing in the Spring.