How to flush sand out of the engine block?

[DieselDogg]

The other day I noticed my temp on the port motor wouldn't go above 130 unless I got up on plane. Took the T stat out and as I suspected, had sand in it that prevented the T stat from closing all the way. Put the T stat in a cup of hot water, it opened, sand fell out. Put everything back, motor got up to normal op temp, then on the next warm up cycle, same thing. Took T stat out again, same thing, more sand.

Local mechanic said I probably have sand in the block and need to flush it out. His recommendation was to remove the drain plug from the bottom of the block and then run the motor for a bit. He also suggested that if that drain plug is too hard to get at, I can try running the motor at ~1500 rpm with T stat removed.

Has anyone ever run into this and do you guys see any issues with either of the methods he recommended? The boat is in the water and I have a 3 point drain system.

Thanks!

 

[Lazy Daze]

You might find that the small hoses that feed the lower water manifold drain setup are clogged up with sand, as well. So draining from the blue plug/orange hose down there may not actually do anything. Yes, I would open things up and run the engine for a while (monitor your temps, but at idle I doubt you'll have anything to worry about as there'll be more water going in than the block drains will drain). You could try just disconnecting the hoses from the block and keep poking the hole to keep it clear, but it would be much more efficient if you remove the fitting as that makes the "drain hole" about twice as big. Monitor temps with your gauges and your hand on the elbow.

It's going to take some time and you may never get it all out. But I would probably alternate between running the engine for a while and then shutting it off and letting it drain. Be sure to clean out those hoses and also the water manifold drain setup! Check the exhaust manifold drain hose for good measure, too.

Might as well do the starboard drain, too (fuel coolers, as well)! And, yes, getting to inboard sides of the engines is going to be mostly be feel! It's not a "hard" job, just time consuming because it's awkward. You may want to remove some outboard accessories to make things a little roomier down there.

The raw water impellers and plates should at least be checked for wear or scoring.

Note... Make sure you take care of this before winterizing (if you do that where you are, that is). Otherwise you will be left with water in the block, even though the water manifold drain will "appear" to have drained everything.

 

[DieselDogg]

Dennis, thanks so much for such a fast and detailed reply! I wanted to clarify I understand, so I have a few questions per below diagram:

(1) - If my assumption is right, this is the block drain fitting / hose that needs to be removed from the block. Then I run the motor for a bit? Is there the same plug on the STBD side? Do I need to do both of them?
(2) - Is this the exhaust manifold drain hose and if it is, do I disconnect it and then again run the motor?
(3) - Clean out these hoses and the drain manifold to the right? Do I again, disconnect one at a time and run the motor?
(g) - Item g on this diagram is marked as Cool Fuel Box. I did not see this on my set up. I have a Gen 3 Cool Fuel, which mounts in front of the Seawater Pump (c). Is Gen 3 Cool Fuel a different set up then?

Thanks again! We have a 3 day trip into San Juans scheduled end of this week and it's no surprise something like this happens.

 

[Lazy Daze]

Dennis, thanks so much for such a fast and detailed reply! I wanted to clarify I understand, so I have a few questions per below diagram:

(1) - If my assumption is right, this is the block drain fitting / hose that needs to be removed from the block. Then I run the motor for a bit? Is there the same plug on the STBD side? Do I need to do both of them? Yes. The fitting is roughly located between the two middle spark plugs, but lower on the block. Just above where the oil pan touches the block. The small hose attaches to a fitting and that fitting is screwed into the block. Yes, both sides.
(2) - Is this the exhaust manifold drain hose and if it is, do I disconnect it and then again run the motor?Yes. On this, though, I might just remove the small hose from the collection pipe (by letter "F"). It's much less likely that the exhaust mani is clogged and if you have a nice, good stream coming from the hose that would suffice and there's no need to go any further on this one. Do that for both small hoses. I would probably do these first to get them "out of the mix". Run the engine for a good 5 minutes, then shut down. Pull the small hoses from that collection manifold. If the hoses drain what seems like a good half gallon or so, they're fine.
(3) - Clean out these hoses and the drain manifold to the right? Do I again, disconnect one at a time and run the motor?It's also less likely that these are clogged. Just open the drain on Letter F and see that it drains (run engine for a few minutes, then shut down) what looks like a few gallons out.
(g) - Item g on this diagram is marked as Cool Fuel Box. I did not see this on my set up. I have a Gen 3 Cool Fuel, which mounts in front of the Seawater Pump (c). Is Gen 3 Cool Fuel a different set up then?Correct, this diagram is from an older set up and is not of your setup. You should find two hoses attached to the back side of the unit, one on top of the other with a single bracket/nut holding them in place. Follow those hoses back to where they attach to the raw water pump hose. Take them off both off and just squirt some water into one of them.

Thanks again! We have a 3 day trip into San Juans scheduled end of this week and it's no surprise something like this happens.

When you remove the two block drains, and run the engine, you'll probably need something to continually pick/poke the hole. Depending on how hard it's packed, a zip tie may work or you may need need something stronger like an allen wrench, or get creative. The plus to a zip tie, once you can get it in there, is that you can push it in quite far as it will bend and go around the corner. I would also plug the block hoses that go to the water collection pipe while you're running the engine with the hoses off - just for good measure.

You may even consider, after you think you have it all cleaned out, replacing the existing small hoses with some clear, vinyl hose - at least temporarily. That way you can easily monitor things. The vinyl hose can be longer - you don't have to try and cut them exactly as the black rubber ones.

FYI, this is something I DON'T like about the quick drain systems. It's very easy for someone (especially someone that may only watch youtube videos on how to winterize) to miss the fact that one of the hoses may be blocked up and not allowing the engine to drain fully.

If you have the time, you can totally get this done and save the trip! Good luck, Dog!

 

[DieselDogg]

Man, you are awesome! Seriously one of the best replies I've seen on any forum. Should be a sticky!

Going to the boat this afternoon to give it a shot. This seems like such a weird problem to me. My slip is the shallowest point of my boating and at the outdrive, water is 6 feet deep. How and where I found this sand is beyond me. I've only had the boat for barely a year, but when I replaced the impellers, or what was left of them, the brass raw water pump housing was badly grooved. I got the SS plates from Aftermarket Marine to address that problem, but that tells me that previous owner had sand going through there. Wonder if it's possible that it's his sand that somehow got dislodged after 40 hours of use.

 

[DieselDogg]

Was able to pull the STBD block drain quick connect hose and then the brass fitting. If anyone ever has to do this, to remove the quick-connect, squeeze it with your fingers and then pull off the fitting. The brass fitting is a 9/16. 12 point box end was the right tool. Ran the motor 4 times. After the first few times I realized that it was probably more effective to increase the RPM as it increased the water flow and pressure. I did it at 1500 and then the last time took it up to 2500 RPM.

On the PORT side, I only disconnected the quick-connect. I could have taken the fitting out, but I started running out of time and looking at the fine sand that came out on the other side, I didn't really see the need. Did the same procedure on the PORT side.

After connecting the hoses back, I ran it and got it up to operating temp. Then let it cool down and pulled the thermostat. It was clean, no sand. Hoping I got it, but the real test will be when we take her out this Fri. I decided to postpone our trip till next week, just to make sure all is good.

I probably got a hand-full of sand out of it (pic above). I still think that it was from the previous owner. Maybe they winterized it with sand in the block, sand solidified and then came loose once I put a new impeller in with wear plates. I just don't boat in anything shallow at all.

Another thing I noticed is that this motor always had lower water pressure than STBD, on the smartcraft gauges. At idle I was getting 0.6 on this one and 1.1 on STBD. After doing this flush, I was at 0.9. I will have to re-verify this when I take her out later this week.

Thanks for your help Dennis!

 

[DieselDogg]

I will post pics of the quick-connect and the brass fitting if anyone ever needs to do this.

 

[DieselDogg]

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[DieselDogg]

Well, turns out that after getting all that sand out through the drain plugs, I still have more sand. Went out for a bit yesterday and same thing. Thermostat stuck open after getting up on plane. I wonder if I'm just not creating enough water pressure while running the motor at 2500 RPM in my slip. When on plane I'm at 3500, which would pump more water through the block, right?

My next thought is to take the thermostat out completely and go run it on plane at 3500 - 4000 RPM. What do you guys think? I can't hurt anything by running the motor without thermostat for 10 min, can I?

 

[Lazy Daze]

Yeah, sand is a pain in the butt. It's usually a time consuming process to get it all out. As the water flows through the block, the sand gets swooshed around and forced into smaller passages. Nope - you won't hurt anything running without the stat - go for it. Another thought... you might even try backflushing the system with a hose from the top down - with the t-stat housing off and block drains removed. Maybe even flush for a few minutes, then let drain, then flush, then drain, etc. In the end, I don't think there's one best way - just keep experimenting!

 

[magstang1]

Ran my first boat for 7 years with no stat. 350 merc. I'd say you're fine for at least 10 min.

 

[DieselDogg]

Yeah, sand is a pain in the butt. It's usually a time consuming process to get it all out. As the water flows through the block, the sand gets swooshed around and forced into smaller passages. Nope - you won't hurt anything running without the stat - go for it. Another thought... you might even try backflushing the system with a hose from the top down - with the t-stat housing off and block drains removed. Maybe even flush for a few minutes, then let drain, then flush, then drain, etc. In the end, I don't think there's one best way - just keep experimenting!

Dennis, just to make sure I understand this, stick the hose into the opening under thermostat housing, right?

 

[Bt Doctur]

Depending on the amount of sand you have a few options.
1 GET RID OF THE QUICK DRAIN SYSTEM ,BLOCK AND MANIFOLD CONNECTIONS
2 Remove the plugs and try to flush the sand out. Make a curved tool from 3/16 brass tubing to stick into the block drains to encourage sand loosening and removal
3 Remove the engine circ pump, remove the upper core plugs and flush downward
4 Remove engine, remove block core plugs and flush engine

 

[Lazy Daze]

Yup, you got it, Dogg. Have a couple "tools" ready to poke the block holes (remember, it's best to remove the actual block fitting so you have a bigger hole). A heavy zip tie is nice since it will bend and go around the corner. But it may not be strong enough to poke through tightly packed sand. So have something stiffer, too. I imagine it's going to take you multiple attempts to get the majority of it out. Every so often, turn the water off and let it drain as much as it will - that could help to let the sand re-accumulate at the bottom, after being swished around. You might even try varying the intensity of the water - a slow trickle, medium, etc, etc. There's no one best way to do it - at least not that I've ever found. Removing the core plugs as the Doc mentioned is a good idea - but check how much room you have to put new ones back in... there may not be enough. But that would be nice since the holes are larger. Good luck!

 

[DieselDogg]

Thanks everyone! So far I've ran the motor with drain plugs removed while docked in my slip and ran without the thermostat on plane for about 30 min. Got about a handful of sand out with plugs removed, but I'm still having a problem. I guess I'm going to keep flushing it more. What a pia

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[DieselDogg]

Depending on the amount of sand you have a few options.
1 GET RID OF THE QUICK DRAIN SYSTEM ,BLOCK AND MANIFOLD CONNECTIONS
2 Remove the plugs and try to flush the sand out. Make a curved tool from 3/16 brass tubing to stick into the block drains to encourage sand loosening and removal
3 Remove the engine circ pump, remove the upper core plugs and flush downward
4 Remove engine, remove block core plugs and flush engine

Doc, Could you elaborate on option 1? How would one go about getting rid of the quick drain system and why would this fix the issue? Thanks

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