3GM Priming water pump?

[CJeffBreen]

I always close the water pump through hole when I'm done sailing. I always open it when I start the engine. Almost always.
About a month ago I started to go out and forgot to open through hull. I can sail back into my slip so I didn't start the engine again.
Finished the days sail and came back a week later. Opened through hull and started motor but, but no water came out the exhaust.
Got the dock hose and tried to prime. Would not start pumping. Put in new impeller. Will not start pumping.
Help? This is an old faithful engine. Always starts. Over the twenty plus years I've owned it I've had a couple impeller issues and that's it.
I rarely run it more than a few minutes. As soon as sails can go up, I sail. Motor has few hours even though it is old.

 

[Clutch Cargo]

First of all, anything I tell you is worth exactly what you've paid for it. This is not a directive but my opinion. Proceed at your own risk.

Assuming that the thru-hull on your vessel is in the proper place, it is below the waterline and subject to positive pressure so there is generally no reason that it would need to be primed. Secondly, the raw water pump on a marine engine is of the flexible impeller type and is in the positive displacement family of pumps. Therefore, generally speaking, it should not need to be primed. If seawater is not flowing through the engine, it is most likely for some other reason.

From what you described, the last thing you touched is the through-hull valve (a.k.a. a seacock) and this may be the culprit. However, determining if this valve is working while the vessel is in the water can have potentially catastrophic results. Your boat is worth more than the price of a short haul. With the vessel on the slings, you can determine if it is working or broken in the closed position, blocked etc. If it is working, then you'll have to look someplace else.

RE: "I rarely run it more than a few minutes. As soon as sails can go up, I sail. Motor has few hours even though it is old."
Second only to running a diesel engine on gasoline, this is probably the worst thing you can do to it. Any piece of machinery is like a good dog and needs to be exercised. What you are doing actually accelerates wear of the bearing, seals, pumps (FW, oil), valves/guides, injectors, gaskets etc. etc. etc. because the engine never gets up to operating temperature. I have had this conversation with numerous sailboat owners who mistakenly believe that because they rarely use the engine, it is perfectly fine; and then are incredulous when it suffers a major breakdown. I motor my boat for an hour on a regular basis so as to avoid these problems.

HTH

 

[Claude L.-Auger]

Good ideas from HTH. However, your marina may not let you work on the boat while in the slings so here are a few things to check before before you go through the cost and hassle of a hauling the boat out:

1) most boats have a skimmer type water filter between the seacock and the impeller pump. Make sure the seacock is shut and clean that filter. You may have picked-up some seaweeds and it's doing its job by blocking access to the pump.

Two people are better for the next 2 suggestions. One controlling the opening/closing of the through-hull
2) if filter is clean, while it's opened open seacock slowly to see if water rises to it. If it's below the water line, you should see water getting into it. If it does you should be good to go, after putting the cover back on the filter. If it's above water line, you'll need to close the cover and start the engine to see if you have water coming through. The impeller pump is self-priming as HTH said.
3) If filter is clean and stll no water, shut the seacock, disconnect the hose at the filter and using a compressor blow some air into the hose with the second person opening the seacock. That should clean whatever is clogging the through-hull. After you hear bubbles going through the water, shut the seacock and reconnect the hose. Then open it again and start engine to check.
If you do not hear bubbles then the seacock itself is the culprit and the boat will indeed need to be hauled-out for it to be replaced. And if you do have to replace it, make sure you get a good quality ball valve.

Last but not least, it's not a bad idea to shut all seacocks, including engine, when leaving the boat. In order to avoid forgetting to turn it back open, leave your engine key on it. That way you'll need to retrieve the key and won't forget to turn the valve open. Good luck !

 

[Clutch Cargo]

I like the idea of leaving the key on the valve handle. BTW, "HTH" stands for Hope This Helps.

 

[Richard19068]

In addition to the above, I assume the old impeller had all its vanes so none had broken loose and blocked any hoses.

Also, over the years there have been several posts about people replacing impellers and having them not pump. Apparently new impellers can sometimes be defective by having the hub of the impeller being loose on the shaft. Rare but a possibility.

ps: As Claude L.-Auger suggests I leave my key on the raw water intake valve handle.

 

[CJeffBreen]

Good ideas from HTH. However, your marina may not let you work on the boat while in the slings so here are a few things to check before before you go through the cost and hassle of a hauling the boat out:

1) most boats have a skimmer type water filter between the seacock and the impeller pump. Make sure the seacock is shut and clean that filter. You may have picked-up some seaweeds and it's doing its job by blocking access to the pump.

Two people are better for the next 2 suggestions. One controlling the opening/closing of the through-hull
2) if filter is clean, while it's opened open seacock slowly to see if water rises to it. If it's below the water line, you should see water getting into it. If it does you should be good to go, after putting the cover back on the filter. If it's above water line, you'll need to close the cover and start the engine to see if you have water coming through. The impeller pump is self-priming as HTH said.
3) If filter is clean and stll no water, shut the seacock, disconnect the hose at the filter and using a compressor blow some air into the hose with the second person opening the seacock. That should clean whatever is clogging the through-hull. After you hear bubbles going through the water, shut the seacock and reconnect the hose. Then open it again and start engine to check.
If you do not hear bubbles then the seacock itself is the culprit and the boat will indeed need to be hauled-out for it to be replaced. And if you do have to replace it, make sure you get a good quality ball valve.

Last but not least, it's not a bad idea to shut all seacocks, including engine, when leaving the boat. In order to avoid forgetting to turn it back open, leave your engine key on it. That way you'll need to retrieve the key and won't forget to turn the valve open. Good luck !

I appreciate all the replies. Seacock is clear. Filter is clean. Water flows up into filter bowl easily. Hoses to pump are clear. There is stuff on this motor i never use. It has a hot water heater attached to the radiator. i don't think that is a problem but it is a complication. Changing radiator fluid is more of an issue. it does have a hose coming out of the radiator that goes up to a valve for bleeding, and comes down to the exhaust manifold. I open this and water shoots out. This time a few gasps of air shot out and then water squirts out. Seems to me enough hot water to spew out the exhaust. I see no water coming out the exhaust. Whenever we start the motor one person looks to see if water is pumping out. I will disconnect the hose going from that valve to the exhaust manifold. Maybe? I sort of can't imagine why, but maybe. Thanks again for all the feedback. I am in salt water, and I do expect issues. My damn engine is reversed. To get in there is an absolute nightmare. Years ago I saw an identical boat in Santa Barbara with a cutout in the cockpit floor. You had complete motor access to a reversed motor. Once you get into your eighties you stop, at least I stop, considering these renovations. Climbing over the top of the engine is not exciting. Takes me weeks to recover every time I do it and I have nightmares I'll have to do it again.

 

[CJeffBreen]

First of all, anything I tell you is worth exactly what you've paid for it. This is not a directive but my opinion. Proceed at your own risk.

Assuming that the thru-hull on your vessel is in the proper place, it is below the waterline and subject to positive pressure so there is generally no reason that it would need to be primed. Secondly, the raw water pump on a marine engine is of the flexible impeller type and is in the positive displacement family of pumps. Therefore, generally speaking, it should not need to be primed. If seawater is not flowing through the engine, it is most likely for some other reason.

From what you described, the last thing you touched is the through-hull valve (a.k.a. a seacock) and this may be the culprit. However, determining if this valve is working while the vessel is in the water can have potentially catastrophic results. Your boat is worth more than the price of a short haul. With the vessel on the slings, you can determine if it is working or broken in the closed position, blocked etc. If it is working, then you'll have to look someplace else.

RE: "I rarely run it more than a few minutes. As soon as sails can go up, I sail. Motor has few hours even though it is old."
Second only to running a diesel engine on gasoline, this is probably the worst thing you can do to it. Any piece of machinery is like a good dog and needs to be exercised. What you are doing actually accelerates wear of the bearing, seals, pumps (FW, oil), valves/guides, injectors, gaskets etc. etc. etc. because the engine never gets up to operating temperature. I have had this conversation with numerous sailboat owners who mistakenly believe that because they rarely use the engine, it is perfectly fine; and then are incredulous when it suffers a major breakdown. I motor my boat for an hour on a regular basis so as to avoid these problems.

HTH

I do run it about fifteen minutes at the dock if I'm going out on a friends boat or varnishing and not sailing. So, it does get run, but without a load. It has been great for more than twenty years. I'm gonna try and figure out when I bought it. i avoid thinking back that far. Thanks again.

 

[JoeWhite]

It appears that the mixing elbow is clogged. Disconnect the hose and put it in a bucket and have someone else run the engine for 5 seconds and see if water runs out normally. If so then turn off the engine and try to unclog it by using a flexible brush. Then reconnect and try. If water comes put of the exhaust hose then you have located the problem, but it is not fixed. Replace the exhaust elbow.

 

[CJeffBreen]

It appears that the mixing elbow is clogged. Disconnect the hose and put it in a bucket and have someone else run the engine for 5 seconds and see if water runs out normally. If so then turn off the engine and try to unclog it by using a flexible brush. Then reconnect and try. If water comes put of the exhaust hose then you have located the problem, but it is not fixed. Replace the exhaust elbow.

And I agree. i did take it off many years ago and thoroughly wire brushed it and put it back on. It has been lovely for many years. Thanks!

 

[Claude L.-Auger]

I like the idea of leaving the key on the valve handle. BTW, "HTH" stands for Hope This Helps.

LOL Sorry I thought they were your initials LMAO !

 

[jssailem]

I agree with @JoeWhite, you have cleared the intake part of the system. Now it’s time to examine the exhaust side.